U.S. patent application number 15/341626 was filed with the patent office on 2017-03-16 for method for recycling of obsolete printed circuit boards.
The applicant listed for this patent is ADVANCED TECHNOLOGY MATERIALS, INC.. Invention is credited to Andre BROSSEAU, Svitlana GRIGORENKO, Ping JIANG, Michael B. KORZENSKI.
Application Number | 20170079146 15/341626 |
Document ID | / |
Family ID | 44201293 |
Filed Date | 2017-03-16 |
United States Patent
Application |
20170079146 |
Kind Code |
A1 |
BROSSEAU; Andre ; et
al. |
March 16, 2017 |
METHOD FOR RECYCLING OF OBSOLETE PRINTED CIRCUIT BOARDS
Abstract
Processes for recycling printed wire boards using
environmentally-friendly compositions, wherein electronic
components, precious metals and base metals may be collected for
reuse and recycling.
Inventors: |
BROSSEAU; Andre; (Montreal,
CA) ; GRIGORENKO; Svitlana; (Montreal, CA) ;
JIANG; Ping; (Danbury, CT) ; KORZENSKI; Michael
B.; (Bethel, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ADVANCED TECHNOLOGY MATERIALS, INC. |
Danbury |
CT |
US |
|
|
Family ID: |
44201293 |
Appl. No.: |
15/341626 |
Filed: |
November 2, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14962250 |
Dec 8, 2015 |
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15341626 |
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13641371 |
Jan 7, 2013 |
9215813 |
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PCT/US2011/032675 |
Apr 15, 2011 |
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14962250 |
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61412628 |
Nov 11, 2010 |
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61412390 |
Nov 10, 2010 |
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61388643 |
Oct 1, 2010 |
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61385586 |
Sep 23, 2010 |
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61376549 |
Aug 24, 2010 |
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61368360 |
Jul 28, 2010 |
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61362118 |
Jul 7, 2010 |
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61324390 |
Apr 15, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02P 70/50 20151101;
Y02P 20/582 20151101; Y10T 29/49815 20150115; C22B 11/046 20130101;
Y02P 10/20 20151101; Y02W 30/50 20150501; C23F 1/44 20130101; C25C
1/20 20130101; C22B 7/008 20130101; H05K 2203/178 20130101; C22B
7/007 20130101; H05K 3/22 20130101; H05K 2203/176 20130101 |
International
Class: |
H05K 3/22 20060101
H05K003/22; C22B 3/00 20060101 C22B003/00; C22B 7/00 20060101
C22B007/00; C25C 1/20 20060101 C25C001/20 |
Claims
1.-38. (canceled)
39. A method of recovering at least one precious metal from a
printed wire board (PWB) comprising solder and at least one
precious metal, said method comprising: (a) contacting a surface of
the PWB with a first composition, wherein the PWB and the first
composition are in a first vessel; (b) agitating said first vessel;
(c) dissolving or solubilizing the solder in the first composition,
wherein the first composition selectively removes the solder
relative to the at least one precious metal; (d) removing the first
composition from the PWB by rinsing; (e) drying the PWB; (f)
contacting the PWB with a leaching composition, wherein the PWB and
the leaching composition are in a second vessel; (g) producing
agitation in said second vessel; (h) dissolving or solubilizing the
at least one precious metal in the leaching composition; (i)
removing the leaching composition from the PWB by rinsing; and (j)
recovering the at least one precious metal from the leaching
composition, wherein the first composition is: (i) substantially
devoid of fluoride salts, ferric nitrate and other ferric salts,
titanium (IV) salts, and abrasive material; (ii) substantially
devoid of fluoride salts, ferric nitrate and other ferric salts,
titanium (IV) salts, and fluoroboric acid; (iii) substantially
devoid of fluoride salts, ferric nitrate and other ferric salts,
abrasive material, and fluoroboric acid; (iv) substantially devoid
of fluoride salts, titanium (IV) salts, abrasive material, and
fluoroboric acid; (v) substantially devoid of ferric nitrate and
other ferric salts, titanium (IV) salts, abrasive material, and
fluoroboric acid; or (vi) substantially devoid of fluoride salts,
ferric nitrate and other ferric salts, titanium (IV) salts,
abrasive material, and fluoroboric acid.
40. The method of claim 39, wherein at least one component is
attached to a surface of the PWB, wherein the at least one
component is selected from the group consisting of transistors,
capacitors, heat sinks, integrated circuits, resistors, integrated
switches, chips, processors, and combinations thereof.
41. The method of claim 40, wherein the at least one component is
attached to the surface of the PWB by solder, and wherein the
dissolving or solubilizing of the solder in the first composition
results in the separation of the at least one component from the
PWB.
42. The method of claim 39, wherein the solder comprises lead, tin
or a lead/tin alloy.
43. The method of claim 39, wherein the first composition comprises
at least one oxidizing agent, nitric acid, and at least one
passivating agent, wherein the at least one passivating agent
comprises a species selected from the group consisting of ascorbic
acid, adenosine, L(+)-ascorbic acid, isoascorbic acid, ascorbic
acid derivatives, citric acid, ethylenediamine, gallic acid, oxalic
acid, tannic acid, ethylenediaminetetraacetic acid (EDTA),
1,2,4-triazole (TAZ), benzotriazole (BTA), tolyltriazole,
5-phenyl-benzotriazole, 5-nitro-benzotriazole,
3-amino-5-mercapto-1,2,4-triazole, 1-amino-1,2,4-triazole,
hydroxybenzotriazole, 2-(5-amino-pentyl)-benzotriazole,
1-amino-1,2,3-triazole, 1-amino-5-methyl-1,2,3-triazole,
3-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole,
3-isopropyl-1,2,4-triazole, 5-phenylthiol-benzotriazole,
halo-benzotriazoles, naphthotriazole 2-mercaptobenzothiazole,
2-mercaptothiazoline, 5-aminotetrazole (ATA),
5-amino-1,3,4-thiadiazole-2-thiol,
2,4-diamino-6-methyl-1,3,5-triazine, thiazole, triazine,
methyltetrazole, 1,5-pentamethylenetetrazole,
1-phenyl-5-mercaptotetrazole, diaminomethyltriazine,
4-methyl-4H-1,2,4-triazole-3-thiol,
5-amino-1,3,4-thiadiazole-2-thiol, benzothiazole, tritolyl
phosphate, indiazole, benzoic acid, boric acid, malonic acid,
ammonium benzoate, catechol, pyrogallol, resorcinol, hydroquinone,
cyanuric acid, barbituric acid and derivatives such as
1,2-dimethylbarbituric acid, alpha-keto acids such as pyruvic acid,
phosphonic acid and derivatives thereof, glycine/ascorbic acid,
Dequest 2000, Dequest 7000, p-tolylthiourea, succinic acid,
phosphonobutane tricarboxylic acid (PBTCA), sodium molybdate,
ammonium molybdate, sodium chromate, potassium chromate, calcium
chromate, barium chromate, sodium tungstate, sodium dichromate,
potassium dichromate, ammonium dichromate, suberic acid, azaleic
acid, sebacic acid, adipic acid, octamethylene dicarboxylic acid,
pimelic acid, dodecane dicarboxylic acid, dimethyl malonic acid,
3,3-diethyl succinic acid, 2,2-dimethyl glutaric acid, 2-methyl
adipic acid, trimethyl adipic acid, 1,3-cyclopentane dicarboxylic
acid, 1,4-cyclohexane dicarboxylic acid, terephthalic acid,
isophthalic acid, 2,6-naphthalene dicarboxylic acid,
2,7-naphthalene dicaroxylic acid, 1,4-naphthalene dicarboxylic
acid, 1,4-phenylenedioxy diacetic acid, 1,3-phenylenedioxy diacetic
acid, diphenic acid, 4,4'-biphenyl dicarboxylic acid,
4,4'-oxydibenzoic acid, diphenylmethane-4,4'-dicarboxylic acid,
diphenylsulfone-4,4'-dicarboxylic acid, decamethylene dicarboxylic
acid, undecamethylene dicarboxylic acid, dodecamethylene
dicarboxylic acid, orthophthalic acid, naphthalenedicarboxylic
acid, paraphenylenedicarboxylic acid, trimellitic acid,
pyromellitic acid, sodium hexametaphosphate, and combinations
thereof.
44. The method of claim 39, wherein the first composition comprises
at least one oxidizing agent, nitric acid, and at least one
passivating agent, wherein the at least one passivating agent
comprises a triazole derivative selected from the group consisting
of 1,2,4-triazole, benzotriazole, tolyltriazole,
5-phenyl-benzotriazole, 5-nitro-benzotriazole,
3-amino-5-mercapto-1,2,4-triazole, 1-amino-1,2,4-triazole,
hydroxybenzotriazole, 2-(5-amino-pentyl)-benzotriazole,
1-amino-1,2,3-triazole, 1-amino-5-methyl-1,2,3-triazole,
3-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole,
3-isopropyl-1,2,4-triazole, 5-phenylthiol-benzotriazole,
halo-benzotriazoles, naphthotriazole, and
4-methyl-4H-1,2,4-triazole-3-thiol.
45. The method of claim 43, wherein the at least one oxidizing
agent comprises ozone, bubbled air, cyclohexylaminosulfonic acid,
hydrogen peroxide, oxone, ammonium peroxomonosulfate, ammonium
chlorite, ammonium chlorate, ammonium iodate, ammonium perborate,
ammonium perchlorate, ammonium periodate, ammonium persulfate,
ammonium hypochlorite, sodium persulfate, sodium hypochlorite,
potassium iodate, potassium permanganate, potassium persulfate,
potassium persulfate, potassium hypochlorite, tetramethylammonium
chlorite, tetramethylammonium chlorate, tetramethylammonium iodate,
tetramethylammonium perborate, tetramethylammonium perchlorate,
tetramethylammonium periodate, tetramethylammonium persulfate,
tetrabutylammonium peroxomonosulfate, peroxomonosulfuric acid, urea
hydrogen peroxide, peracetic acid, sodium nitrate, potassium
nitrate, ammonium nitrate, methanesulfonic acid (MSA),
ethanesulfonic acid, 2-hydroxyethanesulfonic acid,
n-propanesulfonic acid, isopropanesulfonic acid, isobutenesulfonic
acid, n-butanesulfonic acid, n-octanesulfonic acid, benzenesulfonic
acid, 4-methoxybenzenesulfonic acid, 4-hydroxybenzenesulfonic acid,
4-aminobenzenesulfonic acid, 4-nitrobenzenesulfonic acid,
toluenesulfonic acid, hexylbenzenesulfonic acid,
heptylbenzenesulfonic acid, octylbenzenesulfonic acid,
nonylbenzenesulfonic acid, decylbenzenesulfonic acid,
undecylbenzenesulfonic acid, dodecylbenzenesulfonic acid,
tridecylbenzenesulfonic acid, tetradecylbenzene sulfonic acid,
hexadecylbenzene sulfonic acid, 3-nitrobenzenesulfonic acid,
2-nitrobenzenesulfonic acid, 2-nitronaphthalenesulfonic acid,
3-nitronaphthalenesulfonic acid, 2,3-dinitrobenzenesulfonic acid,
2,4-dinitrobenzenesulfonic acid, 2,5-dinitrobenzenesulfonic acid,
2,6-dinitrobenzenesulfonic acid, 3,5-dinitrobenzenesulfonic acid,
2,4,6-trinitrobenzenesulfonic acid, 3-aminobenzenesulfonic acid,
2-aminobenzenesulfonic acid, 2-aminonaphthalenesulfonic acid,
3-aminonaphthalenesulfonic acid, 2,3-diaminobenzenesulfonic acid,
2,4-diaminobenzenesulfonic acid, 2,5-diaminobenzenesulfonic acid,
2,6-diaminobenzenesulfonic acid, 3,5-diaminobenzenesulfonic acid,
2,4,6-triaminobenzenesulfonic acid, 3-hydroxybenzenesulfonic acid,
2-hydroxybenzenesulfonic acid, 2-hydroxynaphthalenesulfonic acid,
3-hydroxynaphthalenesulfonic acid, 2,3-dihydroxybenzenesulfonic
acid, 2,4-dihydroxybenzenesulfonic acid,
2,5-dihydroxybenzenesulfonic acid, 2,6-dihydroxybenzenesulfonic
acid, 3,5-dihydroxybenzenesulfonic acid,
2,3,4-trihydroxybenzenesulfonic acid,
2,3,5-trihydroxybenzenesulfonic acid,
2,3,6-trihydroxybenzenesulfonic acid,
2,4,5-trihydroxybenzenesulfonic acid,
2,4,6-trihydroxybenzenesulfonic acid,
3,4,5-trihydroxybenzenesulfonic acid,
2,3,4,5-tetrahydroxybenzenesulfonic acid,
2,3,4,6-tetrahydroxybenzenesulfonic acid,
2,3,5,6-tetrahydroxybenzenesulfonic acid,
2,4,5,6-tetrahydroxybenzenesulfonic acid, 3-methoxybenzenesulfonic
acid, 2-methoxybenzenesulfonic acid, 2,3-dimethoxybenzenesulfonic
acid, 2,4-dimethoxybenzenesulfonic acid,
2,5-dimethoxybenzenesulfonic acid, 2,6-dimethoxybenzenesulfonic
acid, 3,5-dimethoxybenzenesulfonic acid,
2,4,6-trimethoxybenzenesulfonic acid, and combinations thereof.
46. The method of claim 43, wherein the at least one oxidizing
agent comprises an alkanesulfonic acid selected from the group
consisting of methanesulfonic acid, ethanesulfonic acid,
2-hydroxyethanesulfonic acid, n-propanesulfonic acid,
isopropanesulfonic acid, isobutenesulfonic acid, n-butanesulfonic
acid, and n-octanesulfonic acid.
47. The method of claim 39, further comprising dissolving at least
one base metal using a second composition that selectively
dissolves base metal relative to precious metal.
48. The method of claim 41, further comprising contacting the at
least one component with the leaching composition to dissolve or
solubilize at least one precious metal in the leaching
composition.
49. The method of claim 39, wherein the precious metal comprises
gold.
50. The method of claim 39, wherein the leaching composition
comprises triiodide ions.
51. The method of claim 48, wherein the PWB and/or the at least one
component are crushed prior to contact with the leaching
composition.
52. The method of claim 39, wherein the precious metal comprises
gold and the gold is recovered from the leaching composition using
a disproportionation reaction, a reducing agent, or by
electrowinning.
53. The method of claim 48, wherein the component is rinsed
subsequent to contact with the leaching composition and the rinse
water is treated by high surface area electrowinning using an
undivided cell, wherein precious metals are plated and iodide is
oxidized.
54. The method of claim 39, wherein the leaching composition
comprises at least one oxidizing agent, at least one iodide salt or
hydroiodic acid, water, and at least one metal passivating
agent.
55. The method of claim 54, wherein the at least one oxidizing
agent comprises a species selected from the group consisting of
oxone, sodium persulfate, ammonium persulfate, potassium
persulfate, nitric acid, periodic acid, sodium hypochlorite,
hydrogen peroxide, ferric chloride, ferric nitrate, or combinations
thereof, wherein the at least one iodide salt comprises a species
selected from the group consisting of lithium iodide, sodium
iodide, potassium iodide, ammonium iodide, calcium iodide,
magnesium iodide, and tetraalkylammonium iodides, wherein the alkyl
groups may be the same as or different from one another and are
selected from the group consisting of straight-chained
C.sub.1-C.sub.6 alkyls and branched C.sub.1-C.sub.6 alkyls, and
wherein the at least one passivating agent comprises a species
selected from the group consisting of benzotriazole,
5-aminotetrazole, 1,2,4-triazole, tolyltriazole,
5-phenyl-benzotriazole, 5-nitro-benzotriazole,
3-amino-5-mercapto-1,2,4-triazole, 1-amino-1,2,4-triazole,
hydroxybenzotriazole, 2-(5-amino-pentyl)-benzotriazole,
1-amino-1,2,3-triazole, 1-amino-5-methyl-1,2,3-triazole,
3-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole,
3-isopropyl-1,2,4-triazole, 5-phenylthiol-benzotriazole,
halo-benzotriazoles, naphthotriazole ascorbic acid, sodium
molybdate, and combinations thereof.
56. The method of claim 39, wherein the leaching composition is
substantially devoid of aqua regia and cyanide-containing
components.
57. The method of claim 39, wherein said agitation comprises at
least one of mixing, recirculation, turbulence, vibration, or
sonication.
58. The method of claim 39, wherein the first composition
comprises: (i) methanesulfonic acid, nitric acid, benzotriazole and
water; (ii) methanesulfonic acid, nitric acid, 1,2,4-triazole and
water; (iii) methanesulfonic acid, nitric acid,
1-amino-1,2,4-triazole and water; (iv) methanesulfonic acid, nitric
acid, 1-amino-1,2,3-triazole and water; (v) methanesulfonic acid,
nitric acid, 1-amino-5-methyl-1,2,3-triazole and water; (vi)
methanesulfonic acid, nitric acid, 3-amino-1,2,4-triazole and
water; (vii) methanesulfonic acid, nitric acid,
3-mercapto-1,2,4-triazole and water; (viii) methanesulfonic acid,
nitric acid, 3-isopropyl-1,2,4-triazole and water; (ix)
methanesulfonic acid, nitric acid, 5-aminotetrazole and water; (x)
methanesulfonic acid, nitric acid,
2,4-diamino-6-methyl-1,3,5-triazine and water; (xi) methanesulfonic
acid, nitric acid, ascorbic acid and water; (xii) methanesulfonic
acid, nitric acid, sodium molybdate and water; or (xiiiv)
methanesulfonic acid, nitric acid,
3-amino-5-mercapto-1,2,4-triazole and water.
59. The method of claim 39, further comprising flowing the leaching
composition through an ion-exchange resin to remove base metals
from said composition.
60. The method of claim 47, wherein the at least one base metal
comprises nickel, copper, or combinations thereof.
61. The method of claim 39, wherein the PWB comprises a fiberglass
layer, copper film, and adhesive.
62. The method of claim 61, wherein the adhesive is degraded to
liberate the copper film from the fiberglass layer.
63. The method of claim 41, wherein the at least one component is
reusable or recyclable and are separated accordingly.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/324,390 filed Apr. 15, 2010 in the name of
Svitlana Grigorenko and Andre Brosseau entitled "Method of
Selective Recovery of Precious Metals by the Use of Ultrasonic
Irradiation," to U.S. Provisional Patent Application No. 61/376,549
filed Aug. 24, 2010 in the name of Svitlana Grigorenko and Andre
Brosseau entitled "Methods of Removal of Components on Populated
Circuit Boards by Means of Selective Recovery of Tin, Lead and/or
Lead-Tin Solder Intensified by the Application of Ultrasound," to
U.S. Provisional Patent Application No. 61/412,390 filed Nov. 10,
2010 in the name of Andre Brosseau and Svitlana Grigorenko entitled
"Methods for Recycling of Obsolete Printed Circuit Boards," to U.S.
Provisional Patent Application No. 61/362,118 filed Jul. 7, 2010 in
the name of Michael B. Korzenski and Ping Jiang entitled "Processes
for Reclaiming Precious Metals and Copper from Printed Wire
Boards," to U.S. Provisional Patent Application No. 61/368,360
filed Jul. 28, 2010 in the name of Michael B. Korzenski and Ping
Jiang entitled "Processes for Reclaiming Precious Metals and Copper
from Printed Wire Boards," to U.S. Provisional Patent Application
No. 61/385,586 filed Sep. 23, 2010 in the name of Michael B.
Korzenski and Ping Jiang entitled "Processes for Reclaiming
Precious Metals and Copper from Printed Wire Boards," to U.S.
Provisional Patent Application No. 61/388,643 filed Oct. 1, 2010 in
the name of Ping Jiang and Michael B. Korzenski entitled
"Formulation and Method for Leaching Gold from Material," and to
U.S. Provisional Patent Application No. 61/412,628 filed Nov. 11,
2010 in the name of Andre Brosseau, Svitlana Grigorenko, Ping Jiang
and Michael B. Korzenski entitled "Method for Recycling of Printed
Circuit Boards," each of which is incorporated by reference herein
in their entirety.
FIELD
[0002] The present invention relates generally to processes for
recycling printed wire boards to separate materials including, but
not limited to, precious metals, base metals, solder metals, and
working integrated circuits.
DESCRIPTION OF THE RELATED ART
[0003] Disposal of used electronic equipment including obsolete or
damaged computers, computer monitors, television receivers,
cellular telephones, and similar products, is increasing at a rapid
rate. It is recognized that there are significant hazards to living
things and to the environment generally when electronic equipment
is dumped in landfills. Equally, it is understood that improper
disassembly poses appreciable risks to the health and safety of
people performing disassembly manually.
[0004] Printed wire boards (PWBs) are a common element of many
electronic systems. PWBs are typically manufactured by laminating
dry film on clean copper foil, which is supported on a fiberglass
plate matrix. The film is exposed with a film negative of the
circuit board design, and an etcher is used to remove unmasked
copper foil from the plate. Solder is then applied over the
unetched copper on the board. Depending upon the use and design of
the particular PWB, various other metals may be used in the
manufacturing process, including lead, tin, nickel, iron, zinc,
aluminum, silver, gold, platinum, palladium, and mercury. The PWBs
include many additional components, for example, transistors,
capacitors, heat sinks, integrated circuits (IC's), resistors,
integrated switches, processors, etc.
[0005] PWBs are potentially a difficult waste material to process
since they generally have little usefulness once they are removed
from the electrical system in which they were installed. In
addition, they typically consist of materials that classify them as
a hazardous or "special" waste stream. They must be segregated and
handled separately from other nonhazardous solid waste streams.
PWBs that are handled as waste materials must be processed using
any one of several available disposal options. Not only are these
options expensive, they require a significant amount of effort and
handling by the generator. Furthermore, since some of these
disposal options do not include destruction of the waste circuit
boards, the generator also retains much of the liability associated
with improper handling or disposal.
[0006] Different methods have been suggested to try to combat the
waste of raw materials and environmental pollution caused by the
ever increasing load of scrap electronic waste. To date, methods
requiring a high energy demand are needed to separate the materials
so that they can be recycled. Mechanical and hydrometallurgical
methods have been the traditional methods of recycling of waste
PWBs, which comprise grinding of the whole waste, followed by
attempts to separate and concentrate different material streams.
Disadvantageously, when PWBs are ground, only the plastic fraction
can be effectively liberated from metals and toxic gases are
evolved. Accordingly, mechanical methods do not result in high
recovery rates, especially for precious metals. In
hydrometallurgical methods, large amounts of chemicals are used,
generating huge quantities of waste acids and sludge, which have to
be disposed as hazardous waste. Furthermore, the overall processes
of recycling of various metals by chemical processes are very long
and complicated. Thermal methods, including pyrometallurgical
processing of waste PWBs, result in the emission of hazardous
chemicals to the atmosphere and water as the result of thermal
degradation of epoxy (formation of dioxins and furans) and
volatilization of metals (including Pb, Sb, As and Ga). Thermal
methods are further characterized by high energy consumption, and
the necessity to use expensive exhaust gas purification systems and
corrosion resistance equipment.
[0007] Further, disadvantageously, the present methods of
extracting precious metals (e.g., gold) from materials include
using toxic and/or expensive chemicals (i.e., lixiviants) to leach
the gold from the material. One of the oldest commercial processes
for dissolving gold is the so-called "cyanide process" whereby the
cyanide ion forms such a stable complex with gold. The
effectiveness of the cyanide process has led to its commercial
usage for both extraction of gold from its ores and for the
reclamation of gold from gold coated scrap parts. Generally, a
potassium cyanide solution is used in the "cyanide process."
Disadvantageously, this solution is very toxic and disposing of
spent cyanide solution has become a significant and increasing
waste disposal and pollution abatement control problem. Gold has
also been dissolved using a mixture of hydrochloric acid and nitric
acid, known as "aqua regia," in order to obtain the complex
chlorauric acid, HAuCl.sub.4. Aqua regia, however, is extremely
corrosive, yields toxic fumes, and does not have any selectivity
for precious metals.
[0008] Printed circuit boards without any components and solder
(i.e., bare boards) represent a material that is much easier to
recycle than populated circuit boards with mounted components,
since bare boards by themselves consist only of copper and
fiberglass foils glued by epoxy with some gold/nickel/copper
plating on their surface. As bare board represents 65-70% by weight
of an average populated printed circuit board, removal of
components from the board leads to formation of an
easily-recyclable material fraction, which represents 65-70% of the
total volume. This approach is more advantageous compared to common
practice of size reduction applied to the whole incoming material
volume. Moreover, once removed from the boards, recovered
components may be sorted and sold by type, such as components
containing tantalum or components that can be reused, thereby
generating multiple product streams with a higher retail value than
just a mix of components.
[0009] Thus, a need exists for a method of recycling printed wire
board components and other materials comprising gold or other
precious metals and for recovering the gold or other precious
metals therefrom that overcome or minimize the above-referenced
problems.
SUMMARY
[0010] The present invention relates generally to processes for
recycling printed wire boards to separate materials for reuse
and/or recovery. More particularly, the present invention relates
generally to processes for recycling PWBs to recover precious
metals, base metals, working components, and tantalum metals.
[0011] In one aspect, a method of separating a printed wire board
component from a printed wire board is described. Said method
comprises contacting a first composition with the printed wire
board to selectively remove the printed wire board component from
said printed wire board.
[0012] In another aspect, a first composition that selectively
removes solder, (e.g., lead and/or tin-containing materials)
relative to precious metals, tantalum-containing metals, and/or
base metals is described. The first composition comprises, consists
of, or consists essentially of at least one oxidizing agent,
optionally at least one at least one lead and/or tin complexing
agent, optionally at least one organic solvent, optionally at least
one passivating agent, and optionally a sulfamate ion.
[0013] In still another aspect, a method of removing precious
metals from the surface is described, wherein said precious metals
are undercut from the surface. The method comprises contacting said
surface with a second composition, to selectively remove base
metals relative to the precious metals present on said surface.
[0014] In another aspect, a second composition that selectively
removes base metals such as copper and/or nickel containing
materials relative to precious metals (e.g., gold) is described,
said second composition comprising, consisting of, or consisting
essentially at least one oxidizing agent, optionally at least one
base metal complexing agent, optionally at least one organic
solvent, and optionally at least one passivating agent.
[0015] In still another aspect, a method of recovering precious
metals, e.g., gold, from precious metal-containing materials is
described, wherein said method comprises introducing the precious
metal-containing materials to a leaching composition comprising
triiodide, and optionally introducing ultrasonic cavitation
thereto.
[0016] In yet another aspect, a bare board can be processed to
liberate the fiberglass-epoxy layer from the copper, wherein the
bare board can be processed by degrading the epoxy, which liberates
the copper sheet from the fiberglass.
[0017] In another aspect, a method of processing a printed wire
board (PWB) is described, said method comprising:
(a) separating at least one component from the PWB; and (b)
removing at least one metal, the at least one component, or both
from the PWB.
[0018] In another aspect, a method of removing lead and/or
tin-containing materials from a solid material is described,
wherein said method includes contacting a first composition with
the solid material having the lead and/or tin-containing materials
thereon or therein, under sufficient contacting conditions to
remove the lead and/or tin-containing materials from the solid
material. The solid material includes, but is not limited to,
microelectronic devices, metals, plastics, fabrics, fibers, soils,
ores, wood, paper, glass, leather and other animal hides, cement,
concrete, bricks, drywall, asphalt, keratin-containing substances
such as hair and nails, rubber, latex, and combinations
thereof.
[0019] In a further aspect, a method of removing copper and/or
nickel-containing materials from a solid material is described,
wherein said method includes contacting a second composition with
the solid material having the copper and/or nickel-containing
materials thereon or therein, under sufficient contacting
conditions to remove the copper and/or nickel-containing materials
from the solid material. The solid material includes, but is not
limited to, microelectronic devices, metals, plastics, fabrics,
fibers, soils, ores, wood, paper, glass, leather and other animal
hides, cement, concrete, bricks, drywall, asphalt,
keratin-containing substances such as hair and nails, rubber,
latex, and combinations thereof.
[0020] Other aspects, features and advantages will be more fully
apparent from the ensuing disclosure and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 illustrates a first embodiment of the method of
recycling printed wire boards.
[0022] FIG. 2 illustrates a second embodiment of the method of
recycling printed wire boards.
[0023] FIG. 3 illustrates a third embodiment of the method of
recycling printed wire boards.
[0024] FIG. 4 illustrates a fourth embodiment of the method of
recycling printed wire boards.
[0025] FIG. 5 illustrates a fifth embodiment of the method of
recycling printed wire boards.
DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS THEREOF
[0026] The present invention relates generally to processes for
recycling printed wire boards to separate materials for reuse
and/or recovery. More particularly, the present invention relates
generally to processes for recycling PWBs to recover precious
metals, base metals, working components, and tantalum metals.
Advantageously, the processes described herein are more
environmentally friendly and require less energy than the methods
of the prior art.
[0027] As introduced in the background section, the traditional
methods of recycling of waste PWBs result in environmental
contamination, high cost expenditure and low efficiency. In
contrast, the methods described herein are based on a differential
approach to the recycling of materials, wherein the various parts
of the waste PWBs are separated based on appearance and physical
and chemical properties. The methods described herein can use
sonochemistry to increase the rates of chemical leaching and
mechanical disaggregation, making possible high recovery rates
using low amounts of chemicals. Alternatively, the methods
described herein do not require sonochemistry to effectively and
efficiently recycle the waste PWBs.
[0028] In general, a process of removing at least one recyclable
material from a printed wire board (PWB) is described, said method
comprising at least one of (a), (b), (c), or any combination
thereof:
(a) releasing a component from the PWB; (b) recovering a precious
metal from the PWB and/or PWB component; (c) recovering a base
metal from the PWB.
[0029] For the purposes of the present disclosure, "electronic
waste" or "e-waste" corresponds to computers, computer monitors,
television receivers, electronic pads, cellular telephones, video
cameras, digital cameras, DVD players, video game consoles,
facsimile machines, copiers, MP3 players, and similar products that
have reached the end of their useful life or otherwise have been
disposed of. Electronic waste or e-waste includes the components
contained within these well known items such as printed wire boards
and the components contained thereon (e.g., transistors,
capacitors, heat sinks, IC's, resistors, integrated switches, chips
and processors).
[0030] For the purposes of the general disclosure, the bare board
is described as comprising fiberglass, epoxy and copper foil. As
will be appreciated by the skilled artisan, "fiberglass" is a
glass-reinforced plastic or a glass fiber reinforced plastic and
will correspond to any material that comprises plastic and
glass.
[0031] As used herein, "precious metals" include the metals gold,
silver, platinum, palladium, and alloys comprising same.
[0032] As used herein, "base metals" corresponds to iron, nickel,
zinc, copper, aluminum, tungsten, molybdenum, tantalum, magnesium,
cobalt, bismuth, cadmium, titanium, zirconium, antimony, manganese,
beryllium, chromium, germanium, vanadium, gallium, hafnium, indium,
niobium, rhenium, thallium, alloys comprising same, and
combinations thereof.
[0033] As used herein, "copper" corresponds to Cu(0) metal as well
as alloys comprising Cu(0).
[0034] "Substantially devoid" is defined herein as less than 2 wt.
%, preferably less than 1 wt. %, more preferably less than 0.5 wt.
%, and most preferably less than 0.1 wt. %. "Devoid" corresponds to
0 wt. %.
[0035] As used herein, "about" is intended to correspond to .+-.5%
of the stated value.
[0036] As used herein, "selectively removes solder relative to
precious metals, base metals and/or tantalum-containing metals" or
"selectively removes lead and/or tin-containing materials relative
to precious metals, base metals and/or tantalum-containing metals"
corresponds to a part per million (ppm) removal selectivity of
about 2:1 to about 1,000,000:1, preferably about 100:1 to about
1,000,000:1, more preferably about 1000:1 to about 1,000,000:1, and
most preferably about 10,000:1 to about 1,000,000:1. In other
words, when 2 (or upwards of 1,000,000) ppm of lead and/or
tin-containing materials are removed, no more than 1 ppm of
precious metals, base metals and/or tantalum-containing metals are
removed.
[0037] As used herein, "selectively dissolves base metal relative
to precious metal" or "selectively dissolves base metal relative to
the gold" corresponds to a part per million (ppm) removal
selectivity of about 2:1 to about 1,000,000:1, preferably about
100:1 to about 1,000,000:1, more preferably about 1000:1 to about
1,000,000:1, and most preferably about 10,000:1 to about
1,000,000:1. In other words, when 2 (or upwards of 1,000,000) ppm
of base metals are removed, no more than 1 ppm of gold is
removed.
[0038] As defined herein, "complexing agent" includes those
compounds that are understood by one skilled in the art to be
complexing agents, chelating agents, sequestering agents, and
combinations thereof. Complexing agents will chemically combine
with or physically associate with the metal atom and/or metal ion
to be removed using the compositions described herein.
[0039] For the purposes of the present description, "printed wire
boards" and "printed circuit boards" are synonymous and may be used
interchangeably.
[0040] As used herein, the term "separation" corresponds to the
complete removal of the component(s) from the PWB or the partial
separation of the component(s) from the PWB, wherein the partial
separation of the component from the PWB corresponds to the
weakening of the solder holding the component(s) to the PWB and the
remainder of the separation may be carried out by another
method.
[0041] As used herein, "to remove" solder relative to precious
metals, base metals and/or tantalum-containing metals means that
solder metal or ions are substantially dissolved or otherwise
solubilized in the removal composition, preferably dissolved, while
the precious metals, base metals and/or tantalum-containing metals
are not substantially dissolved or otherwise solubilized.
Analogously, "to remove" base metals relative to the precious
metals means that base metals or ions are substantially dissolved
or otherwise solubilized in the removal composition, preferably
dissolved, while the precious metals are not substantially
dissolved or otherwise solubilized. Further, "to remove" precious
metals from precious metal containing materials means that the
precious metal is substantially dissolved or otherwise solubilized
in the leaching composition, preferably dissolved, while base
metals and/or tantalum-containing metals are not substantially
dissolved or otherwise solubilized. "Substantially dissolved" is
defined herein more than 95 wt. % of the material originally
present is dissolved or otherwise solubilized, preferably more than
98 wt. %, more preferably more than 99 wt. %, and most preferably
more than 99.9 wt. %. "Not substantially dissolved" is defined
herein less than 5 wt. % of the material originally present is
dissolved or otherwise solubilized, preferably less than 2 wt. %,
more preferably less than 1 wt. %, and most preferably less than
0.1 wt. %.
[0042] As used herein, the term "leaches" corresponds to the
complete removal or extraction of the gold or other precious metals
from the PWB and/or PWB component into the leaching composition or
the partial removal or extraction of the gold or other precious
metals from the PWB and/or PWB component into the leaching
composition. The gold or other precious metal is dissolved or
otherwise solubilized in the leaching composition, preferably
dissolved.
[0043] As defined herein, "crushing" the PWB and/or PWB components
corresponds to any method that substantially exposes the gold and
other precious metals of the PWB and/or PWB component to the
leaching composition, e.g., cracking, pulverizing or shredding the
PWB and/or PWB component. Preferably, the PWB components are
cracked, thereby minimizing the amount of gold or other precious
metals lost as a result of the pulverizing or shredding. Precious
metals can be lost if scrap is pulverized wherein gold dust adheres
to the separated stream and is lost in the magnetic fraction.
Accordingly, crushing is further defined as a process whereby no
more than 10% of the gold or other precious metals are lost to
processes such as pulverizing or shredding, preferably no more than
5%, even more preferably no more than 2%. Moreover, crushing the
e-waste minimizes the risk to human health by minimizing the
release of dusts containing hazardous metals and brominated flame
retardants.
[0044] As defined herein, "agitation means" include, but are not
limited to, physical agitation such as mixing, recirculation,
turbulence, vibrations, sonication, and combinations thereof.
[0045] It is well understood to the skilled artisan that "iodine"
corresponds to the I.sub.2 molecule while "iodide" (I.sup.-) is an
anion and is provided as a salt. Iodide salts include, but are not
limited to, lithium iodide, sodium iodide, potassium iodide,
ammonium iodide, calcium iodide, magnesium iodide, and
tetraalkylammonium iodides, wherein the alkyl groups may be the
same as or different from one another and are selected from the
group consisting of straight-chained C.sub.1-C.sub.6 alkyls (e.g.,
methyl, ethyl, propyl, butyl, pentyl, hexyl) and branched
C.sub.1-C.sub.6 alkyls.
[0046] Compositions may be embodied in a wide variety of specific
formulations, as hereinafter more fully described. In all such
compositions, wherein specific constituents of the composition are
discussed in reference to weight percentage ranges including a zero
lower limit, it will be understood that such constituents may be
present or absent in various specific embodiments of the
composition, and that in instances where such constituents are
present, they may be present at concentrations as low as 0.001
weight percent, based on the total weight of the composition in
which such constituents are employed.
Method of Selectively Removing Solder
[0047] Components are typically attached to the surface of PWBs
with a lead, tin or lead-tin solder, which usually comes in
combinations of 70Sn/30Pb, 60Sn/40Pb or 63Sn/37Pb. In certain
applications Ag--Sn solder is used. Currently, the desoldering of
PWBs for component removal involves heating the solder to melting
temperature, whereby the liberated components separate from the PWB
and the liquid solder is collected. This method applied for
recycling PWBs has two main disadvantages: (i) as lead and tin are
low-volatile metals, such heating and melting will create a high
level of polluting emissions to the ambient air; and (ii) the heat
will damage the components making them unacceptable for re-use.
[0048] In a first aspect, a method of separating a printed wire
board component from a printed wire board is described. Broadly,
said method comprises contacting a first composition with the
printed wire board to selectively remove the printed wire board
component from said printed wire board. The printed wire board
component may be attached to the printed wire board using solder or
some other affixing means.
[0049] In one embodiment, a method of removing solder from a
surface is described, wherein said method comprises contacting said
solder with a first composition to selectively remove the solder
relative to metals that are simultaneously present on said surface.
In another embodiment, a method of removing solder from a surface
is described, wherein said method comprises contacting said solder
with a first composition in a vessel, and optionally producing
ultrasonic cavitation or other agitation means in said vessel, to
selectively remove the solder relative to metals that are
simultaneously present on said surface. Preferably, the solder
comprises lead, tin, or a combination of lead and tin. Preferably,
the metals comprise precious metals, tantalum-containing metals,
base metals, or any combination of precious metals,
tantalum-containing metals, and base metals. Preferably, the
surface includes a PWB. Accordingly, in an embodiment, a method of
removing lead and/or tin-containing solder from a PWB is described,
wherein said method comprises contacting said solder with a first
composition in a vessel, and optionally producing ultrasonic
cavitation or other agitation means in said vessel, to selectively
remove the solder relative to precious metals, tantalum-containing
metals, and/or base metals that are simultaneously present on said
PWB. In another embodiment, a method of removing lead and/or
tin-containing solder from a PWB is described, wherein said method
comprises contacting said solder with a first composition in a
vessel, and producing ultrasonic cavitation in said vessel, to
selectively remove the solder relative to precious metals,
tantalum-containing metals, and/or base metals that are
simultaneously present on said PWB. In still another embodiment, a
method of removing lead and/or tin-containing solder from a PWB is
described, wherein said method comprises contacting said solder
with a first composition in a vessel, to selectively remove the
solder relative to precious metals, tantalum-containing metals,
and/or base metals that are simultaneously present on said PWB,
wherein no ultrasonics are used in the process of removing said
solder from the PWB.
[0050] It should be appreciated by the skilled artisan that the
solder attaches "components" such as transistors, capacitors,
resistors, heat sinks, integrated circuits, integrated switches,
processors, chips, etc. to the PWB. Advantageously, new surfaces
(i.e., e-waste PWBs) that require the removal of solder can be then
added to the first composition and the process of removing the
solder to separate the components from the surface can be repeated
until the first composition is saturated with lead and/or tin
metals. With the removal of the solder, the components are released
and said components may be separated using an optical system into
those that are reusable and can be resold and those that can be
further processed for disposal, reclamation of useful materials,
etc. The composition used to remove the solder, which includes lead
and/or tin may undergo electrowinning to reclaim pure lead and/or
tin and/or alternatively can be processed using diffusion dialysis
technology to concentrate the metal ions.
[0051] In removal application when no ultrasonics are produced, the
first composition is contacted in any suitable manner to the PWB,
e.g., by spraying the first composition on the PWB, by dipping (in
a volume of the first composition) of the PWB, by contacting the
PWB with another material, e.g., a pad, or fibrous sorbent
applicator element, that has the first composition absorbed
thereon, by contacting the PWB with a recirculating composition, or
by any other suitable means, manner or technique, by which the
first composition is brought into contact with the material(s) to
be removed.
[0052] In removal application when ultrasound irradiation is
produced, the first composition is contacted to the PWB in a
preferably closed vessel wherein ultrasonic irradiation of the
first composition can be applied to create intensive cavitation.
The frequency of ultrasonic irradiation, the input power and the
ultrasonic amplitude should be chosen in such a way that intensive
cavitation is created in the given volume of irradiated
composition. To obtain a good acceleration of solder removal,
high-powered ultrasound at low frequencies such as 20-40 kHz are
preferred as being responsible for the effects of mechanical
disaggregation. The ultrasound-assisted solder removal process can
be carried out in any embodiment providing access of ultrasonic
irradiation to the composition with immersed PWBs, whereby
intensive cavitation is created in the volume of composition. For
example, the ultrasonic energy can be delivered by an ultrasonic
horn, which is inserted in a preferably closed vessel, containing
the chemical solution (e.g., by UIP1000 hd horn with operational
frequency of 20 kHz by Hielscher Ultrasonics GmbH, which was used
with 1 liter of solution). In this case, however, the PWB
components may not be affected equally because of the different
distance from the horn. The solder removal process should take
place, therefore, either in a small volume, irradiated by the
single ultrasonic horn, making sure that intensive cavitation is
created in the whole volume, or in large volumes, irradiated by
several ultrasonic horns, providing near-equal cavitation intensity
in all parts of the closed vessel. Alternatively, an ultrasonic
bath with vibrating bottom and/or ultrasonic transducers mounted on
the walls can be used to provide equal intensity of ultrasound in
the volume of composition (e.g., a Sonochemical Reaction Vessel
SRV-160 by Advanced Sonics, LLC; SRV-160 is a 5-gallon US bath
driven by 2000 W of ultrasonic power at 20 kHz). In that case,
attention should be paid to provide sufficient ultrasonic power,
since most off-the-shelf ultrasonic baths manufactured for cleaning
applications combine high frequency and low power. There is also an
option to create a special configuration of a flat US horn (e.g.,
as designed by Sonics and Materials Inc.), which enables treatment
of flat items like PWBs. Advantageously, the boards can be conveyed
on a continuous line through the flat sonotrode (similar to
ultrasonic wire cleaning systems such as for example, DRS2000,
manufactured by Hielscher Ultrasonics GmbH. As the intensity of
ultrasound is known to increase with a rise in pressure, better
sonication results can be achieved if light pressure is generated
over the composition surface in the closed vessel. Although not
wishing to be bound by theory, it is thought that chemical
reactions are accelerated by acoustic cavitation by means of
formation of radicals which participate in redox reactions with the
solutes, which dramatically accelerates chemical leaching of tin,
lead and/or tin/lead alloy metals. Acoustic cavitation is also
responsible for the creation of special mechanical effects of
high-speed jets, shear forces and shock waves on the surfaces of
contact, thereby speeding up the mass transfer and mechanical
disaggregation without any mechanical or thermal damage, which
accelerates the separation of mounted components from the surface
of PWBs.
[0053] In use of the compositions described herein for removing
lead and/or tin-containing materials from PWB's having same
thereon, the first composition typically is contacted with the
surface for a time of from about 5 sec to about 180 minutes,
preferably about 1 min to 60 min, and most preferably about 5
minutes to about 45 minutes at temperature in a range of from about
20.degree. C. to about 85.degree. C., preferably in a range from
about 20.degree. C. to about 40.degree. C. Such contacting times
and temperatures are illustrative, and any other suitable time and
temperature conditions may be employed that are efficacious to
remove the materials to be removed from the PWB. After the PWBs
have been exposed to the first composition, with or without
ultrasonic irradiation, the electronic components are liberated,
leaving the bare board with no traces of solder. The components
either drop off or can be removed with minimal force.
[0054] Following the achievement of the desired removal, the first
composition may be readily removed from the PWB to which it has
previously been applied, as may be desired and efficacious in a
given end use application of the compositions described herein.
Preferably, the rinse solution includes deionized water.
Thereafter, the PWB may be dried using nitrogen or a spin-dry
cycle.
[0055] The solder removal process can be repeated with new batches
of PWBs until the first composition is saturated with the ions of
dissolved metals. It is desirable that the first composition is
recycled and reused in new solder removal cycles. It is also
desirable to eventually recover the dissolved metals from the first
composition. There are a number of alternative technologies used
for regeneration of tin and lead from solutions comprising same.
One of them is diffusion dialysis, which takes place in a divided
cell separated by an ion exchange membrane. The membrane allows the
transport of acid and water molecules, but prevents the passing of
metal ions. The acidic solution recovered in this manner can be
immediately reused in the next solder removal cycle, and metals can
be recovered by electrowinning from the concentrated metal
solutions created. A solution comprising tin, lead or tin/lead
alloy can also be regenerated and the metals can be recovered in a
single step by subjecting the solution to electrolysis, whereby the
metals deposit in metallic form on a cathode.
[0056] Advantageously, the method for the separation of electronic
components from the surface of PWBs selectively removes the solder
metals while the precious and base metals and the exposed epoxy of
printed circuit laminate are unaffected. The method provides a fast
and economically efficient process for recycling/reworking waste
PWBs, including reclamation of electronic components and forming a
stream of more easily recyclable bare boards containing only
copper, fiberglass reinforced epoxy and gold/nickel/copper
plating.
An Embodiment of a Composition to Selectively Remove Solder
[0057] In a second aspect, a first composition that selectively
removes solder, (e.g., lead and/or tin-containing materials)
relative to precious metals, tantalum-containing metals, and/or
base metals is described. The first composition for solder removal
has the following qualities: [0058] 1. It is selective as possible
for the dissolution of only lead and tin. PWBs contain large
amounts of different metals, including copper, zinc, aluminum, and
iron. Non-desirable metals would saturate the first composition,
making it less effective for the dissolution of target metals.
[0059] 2. The first composition is effective in dissolving the
solder so the mounted components could rapidly detach from the
surface of PWBs. [0060] 3. The mounted components is recovered in
saleable condition; that means they are preferably not be damaged
or corroded by the first composition. For example, the tiny leads
covered by solder that connect chips to the surface of PWBs are
preferably not be affected. [0061] 4. The first composition removes
gold plating during the process of the first aspect. PWBs contain
metallic gold, which is present in the form of thin plating over
nickel and copper, forming so-called "gold fingers." Accordingly,
the ideal first composition leaves the gold plating unaffected.
[0062] In one embodiment, the first composition comprises, consists
of, or consists essentially of at least one oxidizing agent. The
first composition may further comprise at least one lead and/or tin
complexing agent, at least one organic solvent, and/or at least one
passivating agent for passivating the precious metals,
tantalum-containing metals, and/or base metals. Accordingly, in one
embodiment, the first composition comprises, consists of, or
consists essentially of at least one lead and/or tin complexing
agent in combination with at least one oxidizing agent. In another
embodiment, the first composition comprises, consists of, or
consists essentially of at least one lead and/or tin complexing
agent, at least one oxidizing agent, and at least one passivating
agent for passivating the precious metals, tantalum-containing
metals, and/or base metal materials. In still another embodiment,
the first composition comprises, consists of, or consists
essentially of at least one lead and/or tin complexing agent, at
least one oxidizing agent, and at least organic solvent. In yet
another embodiment, the first composition comprises, consists of,
or consists essentially of at least one lead and/or tin complexing
agent, at least one oxidizing agent, at least one organic solvent,
and at least one passivating agent for passivating the precious
metals, tantalum-containing metals, and/or base metal materials. In
another embodiment, the first composition comprises, consists of,
or consists essentially of at least one oxidizing agent and at
least one organic solvent, wherein the first composition is
substantially devoid of nitric acid, sulfuric acid, or combinations
thereof. In still another embodiment, the first composition
comprises, consists of, or consists essentially of at least one
oxidizing agent and at least one passivating agent for passivating
the precious metals, tantalum-containing metals, and/or base
metals, wherein the first composition is substantially devoid of
nitric acid, sulfuric acid, or combinations thereof. In yet another
embodiment, the first composition comprises, consists of, or
consists essentially of at least one oxidizing agent, at least one
organic solvent, and at least one passivating agent for passivating
the precious metals and/or copper materials, wherein the first
composition is substantially devoid of nitric acid, sulfuric acid,
or combinations thereof. In still another embodiment, the first
composition comprises, consists of, or consists essentially of at
least one oxidizing agent, at least one organic solvent, and at
least one passivating agent for passivating the precious metals,
tantalum-containing metals, and/or base metal materials, wherein
the first composition is substantially devoid of sulfuric acid.
These compositions possess the selectivity of lead and/or
tin-containing materials relative to precious metals,
tantalum-containing metals, and/or base metals thereby increasing
the loading of the bath for the solder and increasing the bath-life
of the first composition. Ion-exchange resins selective to lead
and/or tin can be used in combination with the first composition to
further extend the life of the bath. It should be appreciated that
the first composition is an aqueous composition.
[0063] It should be appreciated by the skilled artisan that the
composition of the second aspect represents just one version of the
first composition of the process of the first aspect. Other
compositions are contemplated for use in the process of the first
aspect, as readily determined by one skilled in the art.
[0064] Oxidizing agents are included in the composition to oxidize
the metals to be removed into an ionic form and accumulate highly
soluble salts of dissolved metals. Oxidizing agents contemplated
herein include, but are not limited to, ozone, nitric acid
(HNO.sub.3), bubbled air, cyclohexylaminosulfonic acid, hydrogen
peroxide (H.sub.2O.sub.2), oxone (potassium peroxymonosulfate,
2KHSO.sub.5.KHSO.sub.4.K.sub.2SO.sub.4), ammonium polyatomic salts
(e.g., ammonium peroxomonosulfate, ammonium chlorite
(NH.sub.4ClO.sub.2), ammonium chlorate (NH.sub.4ClO.sub.3),
ammonium iodate (NH.sub.4IO.sub.3), ammonium perborate
(NH.sub.4BO.sub.3), ammonium perchlorate (NH.sub.4ClO.sub.4),
ammonium periodate (NH.sub.4IO.sub.3), ammonium persulfate
((NH.sub.4).sub.2S.sub.2O.sub.8), ammonium hypochlorite
(NH.sub.4ClO)), sodium polyatomic salts (e.g., sodium persulfate
(Na.sub.2S.sub.2O.sub.8), sodium hypochlorite (NaClO)), potassium
polyatomic salts (e.g., potassium iodate (KIO.sub.3), potassium
permanganate (KMnO.sub.4), potassium persulfate, potassium
persulfate (K.sub.2S.sub.2O.sub.8), potassium hypochlorite (KClO)),
tetramethylammonium polyatomic salts (e.g., tetramethylammonium
chlorite ((N(CH.sub.3).sub.4)ClO.sub.2), tetramethylammonium
chlorate ((N(CH.sub.3).sub.4)ClO.sub.3), tetramethylammonium iodate
((N(CH.sub.3).sub.4)IO.sub.3), tetramethylammonium perborate
((N(CH.sub.3).sub.4)BO.sub.3), tetramethylammonium perchlorate
((N(CH.sub.3).sub.4)ClO.sub.4), tetramethylammonium periodate
((N(CH.sub.3).sub.4)IO.sub.4), tetramethylammonium persulfate
((N(CH.sub.3).sub.4)S.sub.2O.sub.8)), tetrabutylammonium polyatomic
salts (e.g., tetrabutylammonium peroxomonosulfate),
peroxomonosulfuric acid, urea hydrogen peroxide
((CO(NH.sub.2).sub.2)H.sub.2O.sub.2), peracetic acid
(CH.sub.3(CO)OOH), sodium nitrate, potassium nitrate, ammonium
nitrate, and combinations thereof. Although not oxidizing agents
per se, for the sake of the present disclosure, oxidizing agents
further include alkanesulfonic acids (e.g., methanesulfonic acid
(MSA), ethanesulfonic acid, 2-hydroxyethanesulfonic acid,
n-propanesulfonic acid, isopropanesulfonic acid, isobutenesulfonic
acid, n-butanesulfonic acid, n-octanesulfonic acid),
benzenesulfonic acid, benzenesulfonic acid derivatives (e.g.,
4-methoxybenzenesulfonic acid, 4-hydroxybenzenesulfonic acid,
4-aminobenzenesulfonic acid, 4-nitrobenzenesulfonic acid,
toluenesulfonic acid, hexylbenzenesulfonic acid,
heptylbenzenesulfonic acid, octylbenzenesulfonic acid,
nonylbenzenesulfonic acid, decylbenzenesulfonic acid,
undecylbenzenesulfonic acid, dodecylbenzenesulfonic acid,
tridecylbenzenesulfonic acid, tetradecylbenzene sulfonic acid,
hexadecylbenzene sulfonic acid, 3-nitrobenzenesulfonic acid,
2-nitrobenzenesulfonic acid, 2-nitronaphthalenesulfonic acid,
3-nitronaphthalenesulfonic acid, 2,3-dinitrobenzenesulfonic acid,
2,4-dinitrobenzenesulfonic acid, 2,5-dinitrobenzenesulfonic acid,
2,6-dinitrobenzenesulfonic acid, 3,5-dinitrobenzenesulfonic acid,
2,4,6-trinitrobenzenesulfonic acid, 3-aminobenzenesulfonic acid,
2-aminobenzenesulfonic acid, 2-aminonaphthalenesulfonic acid,
3-aminonaphthalenesulfonic acid, 2,3-diaminobenzenesulfonic acid,
2,4-diaminobenzenesulfonic acid, 2,5-diaminobenzenesulfonic acid,
2,6-diaminobenzenesulfonic acid, 3,5-diaminobenzenesulfonic acid,
2,4,6-triaminobenzenesulfonic acid, 3-hydroxybenzenesulfonic acid,
2-hydroxybenzenesulfonic acid, 2-hydroxynaphthalenesulfonic acid,
3-hydroxynaphthalenesulfonic acid, 2,3-dihydroxybenzenesulfonic
acid, 2,4-dihydroxybenzenesulfonic acid,
2,5-dihydroxybenzenesulfonic acid, 2,6-dihydroxybenzenesulfonic
acid, 3,5-dihydroxybenzenesulfonic acid,
2,3,4-trihydroxybenzenesulfonic acid,
2,3,5-trihydroxybenzenesulfonic acid,
2,3,6-trihydroxybenzenesulfonic acid,
2,4,5-trihydroxybenzenesulfonic acid,
2,4,6-trihydroxybenzenesulfonic acid,
3,4,5-trihydroxybenzenesulfonic acid,
2,3,4,5-tetrahydroxybenzenesulfonic acid,
2,3,4,6-tetrahydroxybenzenesulfonic acid,
2,3,5,6-tetrahydroxybenzenesulfonic acid,
2,4,5,6-tetrahydroxybenzenesulfonic acid, 3-methoxybenzenesulfonic
acid, 2-methoxybenzenesulfonic acid, 2,3-dimethoxybenzenesulfonic
acid, 2,4-dimethoxybenzenesulfonic acid,
2,5-dimethoxybenzenesulfonic acid, 2,6-dimethoxybenzenesulfonic
acid, 3,5-dimethoxybenzenesulfonic acid,
2,4,6-trimethoxybenzenesulfonic acid), and combinations thereof.
The oxidizing agents can include a combination of the any of the
species defined herein as oxidizing agent. The oxidizing agent may
be introduced to the first composition at the manufacturer, prior
to introduction of the first composition to the PWB, or
alternatively at the PWB, i.e., in situ. Oxidizing agent is
preferably present in the first composition an amount ranging from
0.1 to 90% by volume, more preferably from 10 to 60% by volume, and
most preferably from 25 to 45% by volume. Preferably, the oxidizing
agent comprises a peroxide compound, oxone, nitric acid and/or
methanesulfonic acid. Most preferably, the oxidizing agent
comprises methanesulfonic acid.
[0065] When present, it is thought that an effective amount of
nitric acid serve as an accelerator of the solder removal process.
Accordingly, in some embodiments, the oxidizing agent in the first
composition preferably comprises an alkane sulfonic acid (e.g.,
MSA) and nitric acid, wherein the alkane sulfonic acid is present
in an amount ranging from 0.1 to 90 vol %, more preferably from 10
to 60 vol %, and most preferably from 25 to 45 vol %, and the
nitric acid is present in an amount of about 0.1 to 80 vol %,
preferably from about 1 to 30 vol %, and most preferably from 5 to
15 vol %.
[0066] The complexing agents are included to complex the ions
produced by the oxidizing agent. Complexing agents contemplated
herein include, but are not limited to: .beta.-diketonate compounds
such as acetylacetonate, 1,1,1-trifluoro-2,4-pentanedione, and
1,1,1,5,5,5-hexafluoro-2,4-pentanedione; carboxylates such as
formate and acetate and other long chain carboxylates; and amides
(and amines), such as bis(trimethylsilylamide) tetramer. Additional
chelating agents include amines and amino acids (i.e. glycine,
serine, proline, leucine, alanine, asparagine, aspartic acid,
glutamine, valine, and lysine), citric acid, acetic acid, maleic
acid, oxalic acid, malonic acid, succinic acid, phosphonic acid,
phosphonic acid derivatives such as hydroxyethylidene diphosphonic
acid (HEDP), 1-hydroxyethane-1,1-diphosphonic acid,
nitrilo-tris(methylenephosphonic acid), nitrilotriacetic acid,
iminodiacetic acid, etidronic acid, ethylenediamine,
ethylenediaminetetraacetic acid (EDTA), and
(1,2-cyclohexylenedinitrilo)tetraacetic acid (CDTA), uric acid,
tetraglyme, pentamethyldiethylenetriamine (PMDETA),
1,3,5-triazine-2,4,6-thithiol trisodium salt solution,
1,3,5-triazine-2,4,6-thithiol triammonium salt solution, sodium
diethyldithiocarbamate, disubstituted dithiocarbamates
(R.sup.1(CH.sub.2CH.sub.2O).sub.2NR.sup.2CS.sub.2Na) with one alkyl
group (R.sup.2=hexyl, octyl, deceyl or dodecyl) and one oligoether
(R.sup.1(CH.sub.2CH.sub.2O).sub.2, where R.sup.1=ethyl or butyl),
ammonium sulfate, monoethanolamine (MEA), Dequest 2000, Dequest
2010, Dequest 2060s, diethylenetriamine pentaacetic acid,
propylenediamine tetraacetic acid, 2-hydroxypyridine 1-oxide,
ethylendiamine disuccinic acid (EDDS),
N-(2-hydroxyethyl)iminodiacetic acid (HEIDA), sodium triphosphate
penta basic, sodium and ammonium salts thereof, ammonium chloride,
sodium chloride, lithium chloride, potassium chloride, ammonium
sulfate, hydrochloric acid, sulfuric acid, and combinations
thereof. Preferably, the complexing agent comprises HEDP, HEIDA,
EDDS, sodium or ammonium salts thereof, sulfuric acid, or
combinations thereof. The amount of oxidizing agent to complexing
agent is in a volume percent ratio range from about 10:1 to about
1:10, preferably about 5:1 to about 1:5, and even more preferably
about 2:1 to about 1:2, wherein the oxidizing agent constituent is
dilute and present in a weight percent of about 1 wt % to about 50
wt %, e.g., a volume of 30 wt % hydrogen peroxide, and the
complexing agent constituent is dilute and present in a weight
percent of about 1 wt % to about 50 wt %, e.g., a volume of 1 wt %
HEDP. For example, the first composition can comprise 1 part by
volume of 30 wt % hydrogen peroxide plus 1 part by volume of a 1 wt
% complexing agent.
[0067] Passivating agents for passivating the precious metals,
tantalum-containing metals, and/or base metals include, but are not
limited to, ascorbic acid, adenosine, L(+)-ascorbic acid,
isoascorbic acid, ascorbic acid derivatives, citric acid,
ethylenediamine, gallic acid, oxalic acid, tannic acid,
ethylenediaminetetraacetic acid (EDTA), uric acid, 1,2,4-triazole
(TAZ), triazole derivatives (e.g., benzotriazole (BTA),
tolyltriazole, 5-phenyl-benzotriazole, 5-nitro-benzotriazole,
3-amino-5-mercapto-1,2,4-triazole, 1-amino-1,2,4-triazole,
hydroxybenzotriazole, 2-(5-amino-pentyl)-benzotriazole,
1-amino-1,2,3-triazole, 1-amino-5-methyl-1,2,3-triazole,
3-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole,
3-isopropyl-1,2,4-triazole, 5-phenylthiol-benzotriazole,
halo-benzotriazoles (halo=F, Cl, Br or I), naphthotriazole),
2-mercaptobenzimidazole (MBI), 2-mercaptobenzothiazole,
4-methyl-2-phenylimidazole, 2-mercaptothiazoline, 5-aminotetrazole
(ATA), 5-amino-1,3,4-thiadiazole-2-thiol,
2,4-diamino-6-methyl-1,3,5-triazine, thiazole, triazine,
methyltetrazole, 1,3-dimethyl-2-imidazolidinone,
1,5-pentamethylenetetrazole, 1-phenyl-5-mercaptotetrazole,
diaminomethyltriazine, imidazoline thione, mercaptobenzimidazole,
4-methyl-4H-1,2,4-triazole-3-thiol,
5-amino-1,3,4-thiadiazole-2-thiol, benzothiazole, tritolyl
phosphate, imidazole, indiazole, benzoic acid, boric acid, malonic
acid, ammonium benzoate, catechol, pyrogallol, resorcinol,
hydroquinone, cyanuric acid, barbituric acid and derivatives such
as 1,2-dimethylbarbituric acid, alpha-keto acids such as pyruvic
acid, adenine, purine, phosphonic acid and derivatives thereof,
glycine/ascorbic acid, Dequest 2000, Dequest 7000, p-tolylthiourea,
succinic acid, phosphonobutane tricarboxylic acid (PBTCA), sodium
molybdate, ammonium molybdate, salts of chromate (e.g., sodium,
potassium, calcium, barium), sodium tungstate, salts of dichromate
(e.g., sodium, potassium, ammonium), suberic acid, azaleic acid,
sebacic acid, adipic acid, octamethylene dicarboxylic acid, pimelic
acid, dodecane dicarboxylic acid, dimethyl malonic acid,
3,3-diethyl succinic acid, 2,2-dimethyl glutaric acid, 2-methyl
adipic acid, trimethyl adipic acid, 1,3-cyclopentane dicarboxylic
acid, 1,4-cyclohexane dicarboxylic acid, terephthalic acid,
isophthalic acid, 2,6-naphthalene dicarboxylic acid,
2,7-naphthalene dicaroxylic acid, 1,4-naphthalene dicarboxylic
acid, 1,4-phenylenedioxy diacetic acid, 1,3-phenylenedioxy diacetic
acid, diphenic acid, 4,4'-biphenyl dicarboxylic acid,
4,4'-oxydibenzoic acid, diphenylmethane-4,4'-dicarboxylic acid,
diphenylsulfone-4,4'-dicarboxylic acid, decamethylene dicarboxylic
acid, undecamethylene dicarboxylic acid, dodecamethylene
dicarboxylic acid, orthophthalic acid, naphthalenedicarboxylic
acid, paraphenylenedicarboxylic acid, trimellitic acid,
pyromellitic acid, sodium phosphates (e.g., sodium
hexametaphosphate), sodium silicates, and combinations thereof.
Most preferably, the passivating agent comprises BTA, ATA, TAZ,
triazole derivatives, ascorbic acid, sodium molybdate, or
combinations thereof. In a particularly preferred embodiment, the
passivating agent comprises sodium molybdate. More particularly,
the role of the passivating agent is to reduce the composition's
attack on copper. This prevents the thin gold plating on the copper
from being undercut and lost as the copper dissolves, and it keeps
such plating safe for a further gold extraction process. When
present, the amount of passivating agent is in a range from about
0.01 to 5 wt %, preferably about 0.1 wt % to about 1 wt %, based on
the total weight of the first composition.
[0068] Although not wishing to be bound by theory, it is thought
that organic solvents enhance the metal etch rates by wetting the
surface of the microelectronic device structure. Organic solvents
contemplated herein include, but are not limited to, alcohols,
ethers, pyrrolidinones, glycols, carboxylic acids, glycol ethers,
amines, ketones, aldehydes, alkanes, alkenes, alkynes, and amides,
more preferably alcohols, ethers, pyrrolidinones, glycols,
carboxylic acids, and glycol ethers such as methanol, ethanol,
isopropanol, butanol, and higher alcohols (including diols, triols,
etc.), tetrahydrofuran (THF), N-methylpyrrolidinone (NMP),
cyclohexylpyrrolidinone, N-octylpyrrolidinone,
N-phenylpyrrolidinone, methyl formate, dimethyl formamide (DMF),
dimethylsulfoxide (DMSO), tetramethylene sulfone (sulfolane),
diethyl ether, phenoxy-2-propanol (PPh), propriopheneone, ethyl
lactate, ethyl acetate, ethyl benzoate, acetonitrile, acetone,
ethylene glycol, propylene glycol, dioxane, butyryl lactone,
butylene carbonate, ethylene carbonate, propylene carbonate,
dipropylene glycol, amphiphilic species (diethylene glycol
monomethyl ether, triethylene glycol monomethyl ether, diethylene
glycol monoethyl ether, triethylene glycol monoethyl ether,
ethylene glycol monopropyl ether, ethylene glycol monobutyl ether,
diethylene glycol monobutyl ether (i.e., butyl carbitol),
triethylene glycol monobutyl ether, ethylene glycol monohexyl
ether, diethylene glycol monohexyl ether, ethylene glycol phenyl
ether, propylene glycol methyl ether, dipropylene glycol methyl
ether (DPGME), tripropylene glycol methyl ether, dipropylene glycol
dimethyl ether, dipropylene glycol ethyl ether, propylene glycol
n-propyl ether, dipropylene glycol n-propyl ether (DPGPE),
tripropylene glycol n-propyl ether, propylene glycol n-butyl ether,
dipropylene glycol n-butyl ether, tripropylene glycol n-butyl
ether, propylene glycol phenyl ether, and combinations thereof),
branched non-fluorinated ether-linkage carboxylic acids
(CH.sub.3CH.sub.2).sub.nO(CH.sub.2).sub.mCOOH, where n=1 to 10 and
m=1 to 10), unbranched non-fluorinated ether-linkage carboxylic
acids (CH.sub.3CH.sub.2).sub.nO(CH.sub.2).sub.mCOOH, where n=1 to
10 and m=1 to 10), branched non-fluorinated non-ether linkage
carboxylic acids (CH.sub.3(CH.sub.2).sub.nCOOH, where n=1 to 10),
unbranched non-fluorinated non-ether linkage carboxylic acids
(CH.sub.3(CH.sub.2).sub.nCOOH, where n=1 to 10), dicarboxylic
acids, tricarboxylic acids, and combinations thereof. Preferably,
the organic solvent comprises diethylene glycol monobutyl ether,
dipropylene glycol propyl ether, propylene glycol, or mixtures
thereof. When present, the amount of organic solvent is in a range
from about 0.01 wt % to about 25 wt %, preferably about 0.1 wt % to
about 10 wt %, and most preferably about 0.1 wt % to about 5 wt %,
based on the total weight of the first composition.
[0069] Typically hydrogen peroxide decomposes upon exposure to
organics or metals, thus, compositions that contain hydrogen
peroxide have a short shelf-life and thus must be mixed at the
point of use. Due to the lack of infrastructure at some user sites,
point of mix use is not an option because of a lack of proper
plumbing and chemical delivery systems, which add cost to a
manufacturing plant. Advantageously, when the first composition
comprises the lead and/or tin complexing agent in combination with
at least one oxidizing agent, the oxidizing agent is stabilized and
thus can be pre-mixed, although it should be appreciated the said
complexing agent and the at least one oxidizing agent may still be
mixed at the point of use.
[0070] In another embodiment, the first composition comprises,
consists of, or consists essentially of: at least one oxidizing
agent; optionally at least one lead and/or tin complexing agent;
optionally at least one organic solvent; optionally at least one
passivating agent for passivating the precious metals,
tantalum-containing metals, and/or base metals; and solder
material. Preferably, the solder material comprises lead and/or
tin-containing materials. The lead and/or tin-containing materials
may be lead and/or tin ions dissolved and/or suspended in the
composition described herein.
[0071] In still another embodiment, when the first composition
includes nitric acid, the composition can further comprise ammonium
sulfamate or sulfamic acid. The sulfamic ions are thought to
stabilize the nitric acid and to suppress the evolution of toxic
NO.sub.x fumes. When present, the amount of sulfamate ion is in a
range from about 0.1 to 20 wt %, preferably of about 1 to 10 wt %,
and most preferably of about 1 to 5 wt %, based on the total weight
of the first composition.
[0072] In a particularly preferred embodiment, the first
composition comprises, consists of, or consists essentially of MSA,
at least one organic solvent, and at least one passivating agent,
wherein the composition is substantially devoid of nitric acid,
sulfuric acid, or combinations thereof. In another particularly
preferred embodiment, the first composition comprises, consists of,
or consists essentially of MSA, at least one glycol ether, and at
least one passivating agent, wherein the composition is
substantially devoid of nitric acid, sulfuric acid, or combinations
thereof. In still another particularly preferred embodiment, the
first composition comprises, consists of, or consists essentially
of MSA, at least one glycol ether, and sodium molybdate, wherein
the composition is substantially devoid of nitric acid, sulfuric
acid, or combinations thereof. Even more preferably, the first
composition comprises, consists of, or consists essentially of MSA,
diethylene glycol monobutyl ether, sodium molybdate, and water,
wherein the composition is substantially devoid of nitric acid,
sulfuric acid, or combinations thereof. In still another
embodiment, the first composition comprises, consists of, or
consists essentially of MSA, at least one organic solvent, and at
least one passivating agent, wherein the composition is
substantially devoid of sulfuric acid. In yet another embodiment,
the first composition comprises, consists of, or consists
essentially of MSA, nitric acid, ammonium sulfamate, BTA,
diethylene glycol monobutyl ether, and water, wherein the
composition is substantially devoid of sulfuric acid. In another
embodiment, the first composition comprises, consists of, or
consists essentially of MSA, nitric acid, ammonium sulfamate, BTA
and water, wherein the composition is substantially devoid of
sulfuric acid. Additional embodiments of the first composition
include (i) a first composition comprising, consisting of or
consisting essentially of MSA, nitric acid, BTA and water; (ii) a
first composition comprising, consisting of or consisting
essentially of MSA, nitric acid, TAZ and water; (iii) a first
composition comprising, consisting of or consisting essentially of
MSA, nitric acid, 1-amino-1,2,4-triazole and water; (iv) a first
composition comprising, consisting of or consisting essentially of
MSA, nitric acid, 1-amino-1,2,3-triazole and water; (v) a first
composition comprising, consisting of or consisting essentially of
MSA, nitric acid, 1-amino-5-methyl-1,2,3-triazole and water; (vi) a
first composition comprising, consisting of or consisting
essentially of MSA, nitric acid, 3-amino-1,2,4-triazole and water;
(vii) a first composition comprising, consisting of or consisting
essentially of MSA, nitric acid, 3-mercapto-1,2,4-triazole and
water; (viii) a first composition comprising, consisting of or
consisting essentially of MSA, nitric acid,
3-isopropyl-1,2,4-triazole and water; (ix) a first composition
comprising, consisting of or consisting essentially of MSA, nitric
acid, MBI and water; (x) a first composition comprising, consisting
of or consisting essentially of MSA, nitric acid, ATA and water;
(xi) a first composition comprising, consisting of or consisting
essentially of MSA, nitric acid,
2,4-diamino-6-methyl-1,3,5-triazine and water; (xii) a first
composition comprising, consisting of or consisting essentially of
MSA, nitric acid, ascorbic acid and water; (xiii) a first
composition comprising, consisting of or consisting essentially of
MSA, nitric acid, sodium molybdate and water; and (xiv) a first
composition comprising, consisting of or consisting essentially of
MSA, nitric acid, 3-amino-5-mercapto-1,2,4-triazole and water.
Another first composition comprises, consists of, or consists
essentially of sulfuric acid, oxone and propylene glycol.
[0073] It was found that the detachment and liberation of
electronic components from the surface of PWBs can be achieved
without addition of ferric nitrate if nitric acid is used in the
first composition. In addition, the first composition can be
substantially devoid of at least one of fluoride salts, other
ferric salts, titanium (IV) salts, abrasive material, fluoroboric
acid, and organic solvents including ethylene groups, e.g.,
ethylene, diethylene, triethylene, etc., and other HAP organic
solvents. As used herein, "fluoride" species correspond to species
including an ionic fluoride (F.sup.-) or covalently bonded
fluorine. It is to be appreciated that the fluoride species may be
included as a fluoride species or generated in situ.
[0074] Advantageously, an easily recyclable chemical composition
can be employed in a closed-loop process generating minimal waste.
For example, when the first composition includes MSA, the MSA is
easily recycled. For example, if the first composition includes
MSA, a glycol ether and sodium molybdate, and said composition is
contacted with Pb/Sn solder, the resulting composition including
the Pb/Sn metals can be recycled by passing the composition through
a carbon filter to remove the glycol ether and electrowinned to
reclaim the Pb and Sn. The remaining solution including MSA can be
reused. When no longer viable, the first composition can be
rendered essentially non-toxic by electrowinning the Pb and Sn and
neutralizing the excess acidity.
[0075] The first composition described can be used to selectively
remove lead and/or tin-containing materials are compatible with the
PWB components, for example, transistors, capacitors, heat sinks,
IC's, resistors, integrated switches, processors, etc., as well as
the precious metals, tantalum-containing metals, and/or base metals
exposed on said PWB. Furthermore, the first compositions are water
soluble, non-corrosive, non-flammable and of low toxicity.
[0076] It should be appreciated that the first composition can be
used at the point of use as formulated or following dilution with
water. Preferably, the diluent is deionized water and the extent of
dilution is about 1:1 to about 10:1 (water to first composition
concentrate).
[0077] The first composition described herein has pH in a range
from about 1 to about 12 and can be adjusted depending on the
complexing agent used (when present). For example, when the
complexing agent comprises HEDP, HEIDA or, salts thereof, the pH of
the composition will be highly acidic, e.g., in a range from about
1 to about 4. When the complexing agent comprises EDDS, the pH of
the composition may be advantageously dialed in by using different
sodium salts of EDDS. For example, compositions comprising EDDS
having three sodium ions will have a pH in a range from about 4 to
about 8, preferably about 5 to about 7. Compositions comprising
EDDS having four sodium ions will have a pH in a range from about 8
to about 12, preferably about 9 to about 11.
[0078] Preferred embodiments of the first compositions described
herein include compositions comprising, consisting or, or
consisting essentially of (i) EDDS/H.sub.2O.sub.2, (ii)
HEIDA/H.sub.2O.sub.2, and (iii) MSA, nitric acid, ammonium
sulfamate, BTA, diethylene glycol monobutyl ether.
[0079] The first compositions described herein are easily
formulated by simple addition of the respective ingredients and
mixing to homogeneous condition. Furthermore, the first composition
may be readily formulated as single-package formulations or
multi-part formulations that are mixed at or before the point of
use, e.g., the individual parts of the multi-part formulation may
be mixed at the tool or in a storage tank upstream of the tool. The
concentrations of the respective ingredients may be widely varied
in specific multiples of the composition, i.e., more dilute or more
concentrated, and it will be appreciated that the compositions
described herein can variously and alternatively comprise, consist
or consist essentially of any combination of ingredients consistent
with the disclosure herein.
Method of Removing Precious Metals by Undercutting Same
[0080] In a third aspect, a method of removing precious metals,
e.g., gold, from a surface is described. It is well known in the
art that PWB's include "gold fingers," which are readily exposed
following the removal of solder and the components (e.g.,
transistors, capacitors, heat sinks, IC's, resistors, integrated
switches, processors, etc.) from the PWB. The gold (as gold
connectors or "gold fingers") overlies base metals such as copper
and/or nickel-containing layers.
[0081] In one embodiment, a method of removing precious metals from
the surface is described, wherein said precious metals are undercut
from the surface. In another embodiment of the third aspect, the
method comprises contacting said surface with a second composition,
to selectively remove base metals relative to the precious metals
present on said surface. The second composition etchingly removes
the base metals (e.g., copper and/or nickel-containing layers) and
undercuts the precious metals (e.g., gold), which delaminates from
the surface and is readily collected (e.g., filtered) for further
processing. Preferably, the surface includes a PWB. In another
embodiment of the third aspect, the method comprises contacting
said surface with a second composition in a vessel, and optionally
producing ultrasonic cavitation or other agitation means in said
vessel, as described hereinabove, to selectively remove base metals
relative to the precious metals present on said surface. In yet
another embodiment, a method of removing precious metals from a
printed wire board is described, wherein said method comprises
contacting said surface with a second composition in a vessel, and
optionally producing ultrasonic cavitation or other agitation means
in said vessel, to selectively remove base metals relative to the
precious metals present on said surface. In another embodiment, a
method of removing precious metals from a printed wire board is
described, wherein said method comprises contacting said surface
with a second composition in a closed vessel, and producing
ultrasonic cavitation in said vessel, to selectively remove base
metals relative to the precious metals present on said surface. In
yet another embodiment, a method of removing precious metals from a
printed wire board is described, wherein said method comprises
contacting said surface with a second composition in a vessel to
selectively remove base metals relative to the precious metals
present on said surface, wherein no ultrasonics are used in the
process of removing precious metals from the PWB.
[0082] Advantageously, new surfaces that have had the solder and
components removed (e.g., according to the process of the first
aspect or the equivalent thereof), that comprise base and precious
metals, can be added to the second composition and the process of
removing the base metals to capture the precious metals can be
repeated until the second composition is saturated with the base
metals. Following completion of the process of the third aspect,
the second composition comprising the base metals can be processed
to obtain useful forms of said base metals (e.g., electrochemically
or by electrowinning). Further, the bare PWB board comprising
fiberglass, copper and epoxy can be processed to liberate the
copper sheets and fiberglass as disclosed herein.
[0083] In another embodiment of the third aspect, a method of
removing precious metals from a printed wire board is described,
wherein said method comprises contacting said surface with a second
composition in a closed vessel, and producing ultrasonic cavitation
in said vessel, to selectively remove base metals relative to the
precious metals present on said surface. Although not wishing to be
bound by theory, it is thought that the ultrasonics create
intensive cavitation, leading to a dramatic increase in removal
efficiency and the creation of special mechanical effects
including, but not limited to, shear forces, high-speed jets and
shock waves, which assist with the removal of the base metals
relative to the precious metals. Although not wishing to be bound
by theory, it is thought that the second composition creates a
tunnelling effect under the precious metals when removing the base
metals. This results in the desired undercutting and subsequent
detachment of the precious metals as a collectable solid, which can
be recovered from the second composition by filtration,
centrifugation, froth flotation or any other appropriate
solid-liquid separation method. The detached precious metals can be
washed with water. Preferably, in this embodiment wherein
ultrasonic cavitation is used, the second composition comprises an
aqueous solution of persulfate salt, e.g., potassium persulfate,
ammonium persulfate, tetramethylammonium persulfate or sodium
persulfate, wherein the concentration of the persulfate salt in the
second composition is in a range from about 0.01 wt % to about 10
wt %, preferably about 0.01 wt % to the limit of solubility. Low
frequency ultrasound (20-40 kHz) is preferred, as the low frequency
would result in the creation of fewer free radicals, which may
contribute to the decomposition of persulfate solutions. It should
be appreciated that known methods of stabilisation of persulfate
solutions may be applied to prevent decomposition of the second
composition, e.g., as disclosed in U.S. Pat. No. 3,644,150, which
is hereby incorporated by reference herein in its entirety. U.S.
Pat. No. 3,644,150 describes a method of stabilizing a leaching
solution using a potassium salt of an organic sulfonic acid,
although it should be appreciated that the utilization of the
teachings of U.S. Pat. No. 3,644,150 are merely optional. The
saturated second composition of this embodiment consists mainly of
copper sulfate. To recover dissolved copper, the working second
composition can be acidified and subjected to electrolysis, or
cooled to precipitate and separate copper sulfate and ammonium
sulfate as claimed in U.S. Pat. No. 3,399,090, which is hereby
incorporated by reference herein in its entirety. U.S. Pat. No.
3,399,090 describes a method of separating a double salt of
dissolved metal sulphate and ammonium sulphate from a solution
comprising same by cooling the solution. It should be appreciated
that the utilization of the teachings of U.S. Pat. No. 3,399,090
are merely optional.
[0084] In removal application when ultrasonic cavitation is not
used, the second composition is contacted in any suitable manner to
the PWB, e.g., by spraying the second composition on the PWB, by
dipping (in a volume of the second composition) of the PWB, by
contacting the PWB with another material, e.g., a pad, or fibrous
sorbent applicator element, that has the second composition
absorbed thereon, by contacting the PWB with a recirculating
composition, or by any other suitable means, manner or technique,
by which the second composition is brought into contact with the
material(s) to be removed. To recover dissolved copper, the working
second composition can be acidified and subjected to electrolysis,
or cooled to precipitate and separate copper sulfate and ammonium
sulphate as described herein.
[0085] In use of the compositions described herein for removing
copper and/or nickel-containing materials from PWB's having same
thereon, the second composition typically is contacted with the
surface for a time of from about 5 sec to about 180 minutes,
preferably about 1 min to 60 min, and most preferably about 5
minutes to about 45 minutes at temperature in a range of from about
20.degree. C. to about 100.degree. C., preferably in a range from
about 20.degree. C. to about 70.degree. C. The temperature can be
higher than 65.degree. C. to prevent formation of solid complex
precipitates when ammonium persulfate is used. Such contacting
times and temperatures are illustrative, and any other suitable
time and temperature conditions may be employed that are
efficacious to remove the materials to be removed from the PWB.
[0086] After the PWBs have been exposed to the second composition,
with or without ultrasonic irradiation, the precious metal has been
liberated, leaving the bare board comprising fiberglass, copper
sheet and epoxy. The precious metal is easily separated from the
second composition comprising solubilized base metal and the
precious metal can be rinsed with water and the rinse water can be
than filtered to recover gold foils. The second composition can
also be filtered to recuperate detached gold foils or a frothing
agent can be added to the second composition and the detached foils
can be skimmed from its surface. The second composition may be
readily removed from the PWB to which it has previously been
applied using a rinse solution. Preferably, the rinse solution
includes deionized water. Thereafter, the PWB may be dried using
nitrogen or a spin-dry cycle. New PWBs having gold thereon (e.g.,
PWBs that have had the components removed) can be added to the
working second composition and the process can be repeated until
the second composition is saturated with base metals. The spent
second composition consists mainly of sulfate of the base metal(s).
To recover dissolved metals, the solution can be acidified and
subjected to electrolysis or electrowinning.
An Embodiment of a Composition for Undercutting Precious Metals
[0087] In a fourth aspect, the second composition that selectively
removes base metals such as copper and/or nickel containing
materials relative to precious metals (e.g., gold) is described,
said composition comprising, consisting of, or consisting
essentially at least one oxidizing agent. The second composition
may further comprise at least one base metal complexing agent, at
least one organic solvent and/or at least one passivating agent for
passivating precious metals. Accordingly, in one embodiment, the
second composition comprises, consists of, or consists essentially
of at least one base metal complexing agent and at least one
oxidizing agent. In another embodiment, the second composition
comprises, consists of, or consists essentially of at least one
oxidizing agent and at least one passivating agent for passivating
precious metals. In yet another embodiment, the second composition
comprises, consists of, or consists essentially of at least one
oxidizing agent and at least one organic solvent. In still another
embodiment, the second composition comprises, consists of, or
consists essentially of at least one base metal complexing agent,
at least one oxidizing agent, and at least one passivating agent
for passivating precious metals. In another embodiment, the second
composition comprises, consists of, or consists essentially of at
least one base metal complexing agent, at least one oxidizing
agent, and at least one organic solvent. Another embodiment of the
second composition comprises, consists of, or consists essentially
of at least one base metal complexing agent, at least one oxidizing
agent, and at least one organic solvent, wherein the composition is
substantially devoid of hydrogen peroxide. In still another
embodiment, the second composition comprises, consists of, or
consists essentially of at least one organic solvent, at least one
oxidizing agent, and at least one passivating agent for passivating
precious metals. In yet another embodiment, the second composition
comprises, consists of, or consists essentially of at least one
base metal complexing agent, at least one oxidizing agent, at least
one organic solvent, and at least one passivating agent for
passivating precious metals. Ion-exchange resins selective to the
base metals can be used in combination with the second composition
to extend the life of the bath. It should be appreciated that the
second composition is an aqueous composition.
[0088] The base metal complexing agents can be selected from the
list of complexing agents described herein, as readily determined
by one skilled in the art. Preferably, the base metal complexing
agents comprise sulfuric acid, chloride salts (e.g., NH.sub.4Cl,
NaCl, KCl, etc.), or combinations thereof. The oxidizing agents may
be selected from the list of oxidizing agents described herein.
Preferably, the oxidizing agent(s) of the second composition
comprise oxone or a persulfate salt, e.g., potassium persulfate,
ammonium persulfate, tetramethylammonium persulfate or sodium
persulfate. The precious metal passivating agents can be selected
from the list of passivating agents described herein, as readily
determined by one skilled in the art. Preferably, the precious
metal (e.g., gold) passivating agent(s) comprise sodium molybdate,
sodium hexametaphosphate, suberic acid, or combinations
thereof.
[0089] It should be appreciated by the skilled artisan that the
composition of the fourth aspect represents just one version of the
second composition of the process of the third aspect. Other
compositions are contemplated for use in the process of the third
aspect, as readily determined by one skilled in the art.
[0090] The amount of oxidizing agent to complexing agent is in a
volume percent ratio range from about 10:1 to about 1:10,
preferably about 5:1 to about 1:5, and even more preferably about
2:1 to about 1:2, wherein the oxidizing agent constituent is
present in a weight percent of about 1 wt % to about 50 wt %, based
on the total weight of the oxidizing agent constituent, and the
complexing agent constituent is present in a weight percent of
about 1 wt % to about 50 wt %, based on the total weight of the
complexing agent constituent. For example, the second composition
can comprise 1 part by volume of 30 wt % hydrogen peroxide plus 1
part by volume of a 1 wt % complexing agent. When present, the
amount of passivating agent is in a range from about 0.01 wt % to
about 5 wt %, preferably about 0.1 wt % to about 1 wt %, based on
the total weight of the second composition. When present, the
amount of organic solvent is in a range from about 0.01 wt % to
about 25 wt %, preferably about 0.1 wt % to about 10 wt %, and most
preferably about 0.1 wt % to about 5 wt %, based on the total
weight of the second composition.
[0091] Advantageously, when the second composition comprises the at
least one base metal complexing agent in combination with at least
one oxidizing agent, the oxidizing agent is stabilized and thus can
be pre-mixed, although it should be appreciated the complexing
agent(s) and the oxidizing agent(s) may still be mixed at the point
of use.
[0092] In another embodiment, the second composition comprises,
consists of, or consists essentially of: at least one oxidizing
agent; optionally at least one base metal complexing agent;
optionally at least one organic solvent; optionally at least one
passivating agent for passivating precious metals; and base metal
materials. Preferably, the base metal materials comprise copper
and/or nickel containing materials. The copper and/or
nickel-containing materials may be copper and/or nickel metals or
ions dissolved and/or suspended in the composition described
herein.
[0093] Preferably, the second composition comprises, consists of,
or consists essentially of oxone and at least one gold passivating
agent. In a particularly preferred embodiment, the second
composition comprises, consists of, or consists essentially of
oxone and sodium molybdate. In another particularly preferred
embodiment, the second composition comprises, consists of, or
consists essentially of oxone and sodium hexametaphosphate. In
still another embodiment, the second composition comprises,
consists of, or consists essentially of oxone, at least one copper
and/or nickel complexing agent, and at least one organic solvent.
For example, the second composition can comprise, consist of, or
consist essentially of oxone, sulfuric acid, and diethylene glycol
monobutyl ether. Alternatively, the second composition can
comprise, consist of, or consist essentially of oxone, sulfuric
acid, and propylene glycol.
[0094] Advantageously, when the second composition includes oxone,
the oxone is easily recycled. For example, if the second
composition includes oxone and sodium molybdate, and said
composition is contacted with Cu/Ni, the resulting composition
including the Cu/Ni ions can be recycled by electrowinning to
reclaim the Cu and Ni. The remaining solution including oxone can
be reused.
[0095] Advantageously, when the second composition includes
sulfuric acid, one of the products is copper sulfate, which can be
reused as copper sulfate or alternatively, electrowon to reclaim
copper metal.
[0096] It should be appreciated that the second composition can be
used at the point of use as formulated or following dilution with
water. Preferably, the diluent is deionized water and the extent of
dilution is about 1:1 to about 10:1 (water to second composition
concentrate).
[0097] The second composition described herein have pH in a range
from about 1 to about 12 and can be adjusted depending on the
complexing agent used (when present). For example, when the
complexing agent comprises HEDP, HEIDA or, salts thereof, the pH of
the composition will be highly acidic, e.g., in a range from about
1 to about 4. When the complexing agent comprises EDDS, the pH of
the composition may be advantageously dialed in by using different
sodium salts of EDDS. For example, compositions comprising EDDS
having three sodium ions will have a pH in a range from about 4 to
about 8, preferably about 5 to about 7. Compositions comprising
EDDS having four sodium ions will have a pH in a range from about 8
to about 12, preferably about 9 to about 11.
[0098] In one embodiment the second compositions are substantially
devoid of fluoride ions. In another embodiment, the second
compositions are substantially devoid of abrasive material.
Further, given the nature of the second compositions, they can be
substantially devoid of organic solvents including ethylene groups,
e.g., ethylene, diethylene, triethylene, etc., and other HAP
organic solvents.
[0099] Preferred embodiments of the second composition described
herein include compositions comprising, consisting or, or
consisting essentially of (i) HEDP/H.sub.2O.sub.2, (ii)
HEIDA/H.sub.2O.sub.2, (iii) sulfuric acid, oxone, diethylene glycol
monobutyl ether, (iv) sulfuric acid, oxone, propylene glycol, (v)
15 wt % sulfuric acid, 12 wt % oxone, 0.8 wt % diethylene glycol
monobutyl ether, (vi) 15 wt % sulfuric acid, 12 wt % oxone, 0.8 wt
% propylene glycol, (vii) 10-20 wt % sulfuric acid, 7-17 wt %
oxone, 0.1-2 wt % diethylene glycol monobutyl ether, and (viii)
10-20 wt % sulfuric acid, 7-17 wt % oxone, 0.1-2 wt % propylene
glycol.
[0100] The second compositions described herein are easily
formulated by simple addition of the respective ingredients and
mixing to homogeneous condition. Furthermore, the second
compositions may be readily formulated as single-package
formulations or multi-part formulations that are mixed at or before
the point of use, e.g., the individual parts of the multi-part
formulation may be mixed at the tool or in a storage tank upstream
of the tool. The concentrations of the respective ingredients may
be widely varied in specific multiples of the composition, i.e.,
more dilute or more concentrated, and it will be appreciated that
the compositions described herein can variously and alternatively
comprise, consist or consist essentially of any combination of
ingredients consistent with the disclosure herein.
Method and Composition for Leaching Precious Metals from Solid
[0101] In a fifth aspect, a composition and a method of recovering
precious metals, e.g., gold, from precious metal-containing
materials is described, wherein said method comprises introducing
the precious metal-containing materials to a leaching composition
comprising triiodide. Said precious metal-containing materials
include, but are not limited to, gold scrap, ores and other mining
tailings and electronic waste (e-waste) such as PWBs and/or PWB
components. In one embodiment, said method of the fifth aspect
comprises introducing precious metal-containing materials to a
leaching composition comprising triiodide in a vessel, and
optionally producing ultrasonic cavitation in said vessel, wherein
said leaching composition comprises triiodide, and wherein the
precious metal is substantially removed from said precious
metal-containing material. Preferably, the precious metal comprises
gold. For example, following the removal of solder and the release
of components from the surface of a PWB (e.g., according to the
method of the first aspect or the equivalent thereof), the
components may be separated into fractions using an optical system
or some other means whereby the reusable components may be
separated from precious metal-containing component fraction, the
base metal-containing component fraction, and optionally the
tantalum-containing component fraction. In one embodiment, the
precious metal containing component fraction is further processed
and the precious metal is leached from the PWB component
fraction.
[0102] In another embodiment, the method of the fifth aspect
corresponds to a method of recovering precious metals, e.g., gold,
from PWB components, wherein said method comprises: introducing the
PWB components to a leaching composition comprising triiodide, and
optionally producing ultrasonic cavitation in said leaching
composition, wherein the precious metals are substantially removed
from said PWB components. The PWB components can be processed as
is, or the PWB components may be crushed as defined herein.
[0103] In another embodiment, the method of the fifth aspect
corresponds to a method of recovering precious metals, e.g., gold,
from printed wire boards, wherein said method comprises:
introducing the PWBs to a leaching composition comprising
triiodide, and optionally producing ultrasonic cavitation in said
leaching composition, wherein the precious metals are substantially
removed from said PWBs. When recovering precious metals from the
PWBs, the PWBs are preferably devoid of the PWB components (e.g.,
the components can be removed using the method of the first aspect
described herein or any other method known in the art). The PWBs
can be processed as is, or the PWBs may be crushed as defined
herein.
[0104] It should be appreciated that the precious metal containing
materials can be added to the leaching composition as is,
pulverized into a powder, shredded into pieces, crushed such that
the hard shell (e.g., plastic) is cracked and the metals contained
therein exposed, or in any other form so long as the metals
contained in the precious metal containing materials are readily
exposed for removal from the materials. Preferably, the precious
metal containing materials is crushed so that the reclamation yield
is increased.
[0105] In use of the compositions described herein for leaching
precious metals from precious metal containing materials, the
composition of the fifth aspect typically is contacted with the
precious metal containing materials for a time of from about 5 sec
to about 180 minutes, preferably about 1 min to 60 min, and most
preferably about 5 minutes to about 45 minutes at temperature in a
range of from about 20.degree. C. to about 60.degree. C.,
preferably in a range from about 20.degree. C. to about 40.degree.
C. Such contacting times and temperatures are illustrative, and any
other suitable time and temperature conditions may be employed that
are efficacious to remove precious metals from the precious metal
containing materials. After the precious metal containing materials
have been exposed to the leaching composition of the fifth aspect,
with or without ultrasonic irradiation, the precious metal will be
liberated.
[0106] In one embodiment, the precious metal removed from the
precious metal containing materials is collected as solid metal
without the necessity to use electrowinning or reducing agents
according to the chemical reactions below which includes the
ionization of gold by the tri-iodide solution to form stable
complexes with gold according to:
2Au+I.sub.3.sup.-+I.sup.-.fwdarw.2AuI.sup.-.sub.2
2Au+3I.sub.3.sup.-.fwdarw.2AuI.sub.4.sup.-+I.sup.-
wherein the trivalent gold complex is in equilibrium with the
monovalent gold complex according to:
AuI.sub.4.sup.-+I.sup.-.fwdarw.AuI.sub.2.sup.-+I.sub.3.sup.-
The gold can be precipitated based on the disproportionation
reaction, as readily understood by the skilled artisan:
3AuI.sub.2.sup.-.fwdarw.2Au.sup.0+AuI.sub.4.sup.-+2I.sup.-
Metallic gold can appear on the surface of the leaching composition
in the form of tiny flakes.
[0107] Addition of metallic gold foils (e.g., seeding) as well as
cooling of the solution, although not obligatory, can increase the
rate of gold removal. To facilitate gold removal, flocculating
agent can be added to the composition (e.g., Magnaflok-351, Ciba
Chemicals) and skimmed from the surface of the leaching composition
together with gold particles. Advantageously, because reducing
agents are not required to obtain the gold metal, new
gold-containing material can be brought in contact with the
tri-iodide leaching composition until the composition becomes
saturated with leached metal again and new gold flakes appear on
the surface for recovery, and so on. Advantageously, the
disproportionation reaction is specific to gold over base metals
and as such, no base metals will auto precipitate at the same time
with gold. Accordingly, no additional measures for reducing the
removal of base metals into the leaching composition are needed.
Advantageously, the recovery of gold will not affect the leaching
composition which can be reused infinitively for leaching of new
precious metal containing material.
[0108] In another embodiment, a reducing agent is added to the
leaching composition containing precious metals removed from the
precious metal containing material to cause their precipitation.
Depending on the precious metal content, various reducing agents
can be applied to cause selective or non-selective precipitation of
precious metals. Precipitation can be done in a manner to avoid the
contamination of the leaching composition, so that the leaching
composition can be regenerated and reused in the next leaching
cycle after the precious metals have been removed. Preferably, the
reducing agent is a so-called environmentally friendly chemical.
Moreover, preferably the reduction occurs rapidly with minimal
heating requirements. For example, precipitation with SO.sub.2 is
known to be selective for gold, non-contaminating to the leaching
composition and inexpensive. Gold is precipitated as a fine powder
that is separated from the leaching solution by filtration. To
facilitate filtration, a flocculating agent can be added to the
solution at the same time as the reducing agent, if the reducing
agent is in liquid or gaseous form. If the reducing agent is in the
form of powder, a flocculating agent can be added after complete
dissolution of the reducing agent to prevent collection of
particles of the reducing agent. For separation of gold powder,
commercially available MAGNAFLOK-351 (Ciba Specialty Chemicals)
that is typically used for concentrating finely ground gold ores,
can be used. The use of a non-ionic flocculating agent is preferred
to avoid the possible undesirable recovery of iodine from the
composition.
[0109] Alternatively, the reducing agents can include, but are not
limited to, sodium borohydride, ascorbic acid, diethyl malonate,
sodium metabisulfite, polyphenon 60 (P60, green tea extract),
glucose, and sodium citrate. For example, as introduced in U.S.
Provisional Patent Application No. 61/375,273 filed on Aug. 20,
2010 and entitled "Sustainable Process for Reclaiming Precious
Metals and Base Metals from e-Waste," which is hereby incorporated
by reference herein in its entirety, ascorbic acid introduced to a
composition comprising Au.sup.3+ ions at pH 1 produces highly pure
gold metal. Sodium metabisulfite (SMB) can be added to a
composition comprising Au.sup.3+ ions at pH 1 or pH 7 and produce
highly pure gold metal. Alternatively, the gold ions can be
converted to gold metal via electrowinning or electrochemical
techniques. Any suitable means can be used to remove the
precipitated gold. Settling and decanting, filtering the solution
through a filter press or centrifuging are convenient procedures
for such removal.
[0110] After separation of the solid gold by filtering,
centrifugation or any other appropriate method, the leaching
composition may still include leached silver and palladium ions. A
selective reducing agent may be added for precipitation of silver,
such as hydroxylamine. The use of a flocculating agent is suggested
to facilitate filtration. After separation of precipitated silver,
only palladium will remain in the leaching solution and can be
precipitated, for example, with the use of a stabilized alkali
metal borohydride and a flocculating agent.
[0111] Although during the precious metal leaching process the
dissolution of base metals is generally inhibited, some base metals
can still accumulate in the composition after several repetitive
leaching cycles. In order to remove these base metals, the leaching
composition can be flowed through a packed column containing
ion-exchange resins, where the dissolved base metals will be
selectively captured, while the tri-iodide ions and the dissolved
precious metals will pass through. The resins that can be used for
this purpose are commercially available, strongly acidic cation
exchangers (e.g., DOWEX ion exchange resins manufactured by The Dow
Chemical Company). The purification of the leaching composition by
base metal removal need not be a part of each leaching cycle, but
can be repeated as often as the solution becomes polluted to the
point that its effectiveness is negatively affected.
[0112] As soon as the leaching process is over and the loaded
tri-iodide solution is separated from the leached material, the
leached material can be rinsed (e.g., with water) to recover the
leaching composition, which can contain very significant amounts of
tri-iodide and dissolved gold.
[0113] Electrowinning is a common way of gold recovery from
solutions, but if the rinse water comprising dissolved gold is
recovered, conventional electrowinning becomes ineffective as gold
is present in rinse water in small concentrations. The removal of
gold from rinse water solutions can become effective if high
surface area (HSA) electrodes are used for electrowinning. HSA
electrowinning may economically remove gold having a concentration
greater than 10 ppm down to ppb level. Iodide can also be oxidized
and recovered using the same process if an undivided electrowinning
cell is used.
[0114] Alternatively, the gold-iodide complex from rinse water can
be captured on ionic exchange resins, although gold and iodide will
be absorbed on the resins together. To absorb the gold-iodide
complex, strongly basic anion exchange resin (e.g., AMBERLITE IRA
410 from DOW) can be used. Gold cannot be easily eluted from these
resins and, if used, in most cases the resins are burned off for
gold recovery. The elution procedure may be facilitated as
described in U.S. Pat. No. 5,051,128, which is mentioned here as a
reference, wherein the gold-iodide complex can be easily eluted if
strongly basic anion exchange resins are pre-treated with sulfuric
acid and sodium nitrite. Elution itself takes place by reacting
with sodium sulfite. This method offers the possibility to
economically treat large amounts of diluted rinse water.
[0115] If for any reason the leaching composition must be
discarded, all the dissolved iodide can be recovered in the form of
iodine. The iodine can than be reused as make up additions to the
newly prepared leaching solution. For iodine recovery, either
oxidation of iodide to its solid state, or iodine recovery on the
special resins can be used. For example, the reaction of hydrogen
peroxide, ozone or sodium, potassium or ammonium persulfate with an
aqueous solution of an iodide leads to the oxidation of iodide ions
to iodine. For the recovery of iodine on resins, commercially
available metal hydroxide loaded ion exchange resins such as DOWEX
G-26 (H) (The Dow Chemical Company) can be used.
[0116] The tri-iodide ion can be introduced in the leaching
composition of the fifth aspect by any known method including, but
not limited to: dissolution of iodine in an aqueous solutions of
iodides (e.g., KI, Nal, NH.sub.4I) or hydroiodic acid; in situ
generation of iodine which reacts with excess iodide to form
triiodide; oxidation of aqueous solutions of iodides by nitric
acid, ozone, hypochlorite and the like; irradiation of aqueous
solutions of iodides by ultrasound; and reaction of an iodide with
an iodate in acidic media. Several are described at length
below.
(a) Generation of Triiodide Using Ultrasound
[0117] In yet another embodiment of the fifth aspect, a composition
and a method of removing gold or other precious metals from e-waste
is described, said method comprising contacting the e-waste with a
leaching composition to leach gold or other precious metals from
said e-waste, wherein ultrasonic irradiation of the leaching
composition is applied. The desired effect can be achieved by: a)
using a tri-iodide leaching composition that can serve as a
selective leachant for precious metals, b) keeping the pH of the
leaching composition only slightly acidic (preferably at least
around pH=5, and more preferably close to acid-neutral) and the
oxidation-reduction potential (ORP) between 100 and 900 mV to
minimize the dissolution of base metals, c) adding special
chemicals such as dibasic ammonium phosphate or dibasic potassium
phosphate/phosphoric acid to prohibit the dissolution of base
metals, and d) passing the composition through commercially
available strong acid cation exchange resins, which will capture
base metals but let tri-iodide and precious metals pass
through.
[0118] The tri-iodide ions are formed directly upon the application
of ultrasound in an aqueous composition containing only iodide,
with no iodine initially present. Although not wishing to be bound
by theory, it is thought that the irradiation of an aqueous
solution of iodide ions with intense ultrasound results in the
creation of hydroxyl radicals, which react with the iodide ions of
the dissolved compound to liberate molecular iodine in situ.
Molecular iodine then combines with the excess iodide present in
the solution to form the brown coloured tri-iodide. For example, it
is known that the release of iodide and the specific colour of the
solution can serve as the indicators of cavitation created by
ultrasonic irradiation. Using the in situ generated tri-iodide,
gold is oxidized and forms the stable complexes AuI.sub.2.sup.- and
AuI.sub.4.sup.- with iodine.
[0119] Advantageously, the application of ultrasound consists in
providing a solution for precious metals leaching that does not
require periodic re-oxidation to maintain the presence of the
triiodide ions, as the triiodide is generated by oxidation of the
iodide upon irradiation of ultrasound into the solution.
[0120] Besides chemical effects, consisting mainly of the formation
of radicals in ultrasonically irradiated solutions, sonication also
has mechanical effects on the chemical reaction, such as increasing
the surface area between the reactants, accelerating dissolution
and renewing the surface of a solid reactant. Cavitation, generated
by ultrasound, has dramatic effects on the reactivities of
solutions. Cavity collapse near an extended solid surface drives
high-speed jets of liquid into the surface and creates shockwave
damage. Shear forces, jets and shock waves result in rapid mass
transfer, surface cleaning and metal activation. Micro jet impacts
on the surfaces effectively remove any passivating coatings as
surface oxides or contaminants, which dramatically increases
reaction rates. Acoustic cavitation results in an enormous
concentration of energy, i.e., very high local temperatures and
pressures created under ultrasound irradiation. Cavitation collapse
produces intense local heating (5000 K), high pressures (1000 atm),
enormous heating and cooling rates (>109 K/sec) and liquid jet
streams (-400 km/h).
[0121] Advantageously, the application of ultrasound results in the
continuous generation of tri-iodide by oxidation of the iodide.
Moreover, the following results can be achieved by creation of
cavitation upon application of ultrasonic irradiation to the
leaching composition for the recovery of precious metals from
precious metal-containing e-waste: a) increase in reaction speed,
b) increase in reaction output, c) ability to conduct the process
at ambient temperatures and atmospheric pressure with short
leaching times, d) utilization of only one chemical selected from
the list including hydroiodic acid or any water-soluble iodide for
the preparation of the leaching composition.
[0122] The leaching process may be organized for a batch process or
a continuous process using an ultrasonic flow cell reactor. In the
latter case, all input material pass through the reactor and are
treated equally. When using a continuous flow process, a certain
optimal combination of slurry flow rate, sonication amplitude and
power can be found. Depending on the type of material and its
precious metal content, different residence times in the ultrasound
reactor may be required until the complete leaching of precious
metals from the material is detected. The time of exposure of the
material is determined by the material feed rate and the volume of
the reactor. Several ultrasonic cell reactors may be used connected
one after one to scale up the process efficiency.
[0123] After passing through the ultrasonic leaching reactor, a
mixture of the treated material and the leaching solution can be
forwarded to a vibrating screen for the separation of coarse
particles. Fines are then separated from the leaching solution with
the use of a pressure filter. Coarse and fine particles are
subsequently rinsed with water to remove all the iodide residues.
Wash water containing small amounts of triiodide is treated with
ozone that oxidizes tri-odide to molecular iodine, which is
collected in a gravity settler and is removed with the use of a
polishing filter. Iodine recovered in this manner can be reused as
a make up chemical in the next leaching cycle, as iodine dissolves
in the aqueous solution of a soluble iodide or hydroiodic acid.
Purified water may be used for the next rinse or for washing
precious metals separated from the leaching solution before sending
them to the oven. Clean coarse and fine particles, which do not
contain any precious metals, can be sent to the next stage for
recycling of base metals.
[0124] Depending on the precious metal content, various reducing
agents can be applied to cause selective or non-selective
precipitation of the precious metals from the leaching composition.
Precipitation can be done in a manner to avoid the contamination of
the leaching composition, so that the leaching composition can be
regenerated and reused in the next leaching cycle after the
precious metals have been removed. For example, precipitation with
SO.sub.2 is known to be selective for gold, non-contaminating to
the leaching composition and inexpensive. Gold is precipitated as a
fine powder that is separated from the leaching solution by
filtration. To facilitate filtration, a flocculating agent can be
added to the solution at the same time as the reducing agent, if
the reducing agent is in liquid or gaseous form. If the reducing
agent is in the form of powder, a flocculating agent can be added
after complete dissolution of the reducing agent to prevent
collection of particles of the reducing agent. For separation of
gold powder, commercially available MAGNAFLOK-351 (Ciba Specialty
Chemicals) that is typically used for concentrating finely ground
gold ores, can be used. The use of a non-ionic flocculating agent
is preferred to avoid the possible undesirable recovery of iodine
from the composition.
(b) Generation of Iodine In Situ
[0125] In another embodiment, a method of removing gold or other
precious metals from e-waste, e.g., PWBs and/or PWB components is
described, said method comprising generating iodine (I.sub.2) in
situ to form a leaching composition comprising the in situ
generated iodine, and contacting the PWBs and/or PWB components
with the leaching composition to leach gold or other precious
metals from the PWBs and/or PWB components. Preferably, the PWBs
and/or PWB components are crushed prior to contact with the
leaching composition. In a preferred embodiment, the method further
comprises separating the leaching composition comprising the gold
or other precious metals from the e-waste. Solid metal can be
obtained by reducing the gold or other precious metals in the
leaching composition (e.g., with a reducing agent suitable for such
purpose). Advantageously, the method can be run at room
temperature. Preferably gold is the precious metal separated from
the e-waste.
[0126] In yet another embodiment, a method of removing gold or
other precious metals from PWBs and/or PWB components is described,
said method comprising generating iodine (I.sub.2) in situ to form
a leaching composition comprising the in situ generated iodine,
contacting the PWBs and/or PWB components with the leaching
composition to leach gold or other precious metals from the PWBs
and/or PWB components, and separating the leaching composition
comprising the gold or other precious metals from the PWBs and/or
PWB components. Solid metal can be obtained by reducing the gold
ions in the leaching composition (e.g., with a reducing agent
suitable for such purpose). Preferably, the PWBs and/or PWB
components are crushed prior to contact with the leaching
composition.
[0127] In another embodiment, a method of removing gold or other
precious metals from PWBs and/or PWB components is described, said
method comprising generating iodine (I.sub.2) in situ to form a
leaching composition comprising the in situ generated iodine,
contacting the PWBs and/or PWB components with the leaching
composition to leach gold or other precious metals from the PWBs
and/or PWB components, separating the leaching composition
comprising the gold or other precious metals from the PWBs and/or
PWB components, and reducing the gold ions in the leaching
composition to form solid gold. Preferably, the PWBs and/or PWB
components are crushed prior to contact with the leaching
composition.
[0128] In yet another embodiment, a method of separating gold or
other precious metals from a material comprising at least one base
metal is described, said method comprising contacting a material
comprising the gold or other precious metals and the at least one
base metal with a composition under conditions to leach the gold or
other precious metals from said material into a leaching
composition, wherein said leaching composition comprises, consists
of, or consists essentially of at least one oxidizing agent, at
least one iodide salt or hydroiodic acid, water, optionally at
least one organic solvent, optionally at least one surfactant, and
optionally at least one passivating agent. In another aspect, the
method further comprises separating the leaching composition
comprising the gold or other precious metals from the material.
Solid gold metal can be obtained by reducing the gold in the
leaching composition (e.g., with a reducing agent suitable for such
purpose).
[0129] Iodine (I.sub.2) is very expensive and has low solubility in
water but it can be generated in situ. Iodine in an aqueous
solution of iodide is present as the triiodide ioin. The process
utilizes iodine to oxidize the gold while iodide contributes to
solubilizing the oxidized gold by formation of a gold iodide
complex.
[0130] In one embodiment, the leaching composition comprises,
consists of, or consists essentially of at least one oxidizing
agent, at least one iodide salt or hydroiodic acid and water. In
another embodiment, the leaching composition comprises, consists
of, or consists essentially of at least one oxidizing agent, at
least one iodide salt or hydroiodic acid, water, optionally at
least one organic solvent, optionally at least one metal
passivating agent, optionally at least one surfactant, optionally
at least one buffering agent. In another embodiment, the leaching
composition comprises, consists of, or consists essentially of at
least one oxidizing agent, at least one iodide salt or hydroiodic
acid, water, and at least one organic solvent. In still another
embodiment, the leaching composition comprises, consists of, or
consists essentially of at least one oxidizing agent, at least one
iodide salt or hydroiodic acid, water, and at least one metal
passivating agent. In still another embodiment, the leaching
composition comprises, consists of, or consists essentially of at
least one oxidizing agent, at least one iodide salt or hydroiodic
acid, water, at least one metal passivating agent, and at least one
buffering agent. In still another embodiment, the leaching
composition comprises, consists of, or consists essentially of at
least one oxidizing agent, at least one iodide salt or hydroiodic
acid, water, and at least one surfactant. In yet another
embodiment, the leaching composition comprises, consists of, or
consists essentially of at least one oxidizing agent, at least one
iodide salt or hydroiodic acid, water, at least one organic
solvent, and at least one metal passivating agent. In yet another
embodiment, the leaching composition comprises, consists of, or
consists essentially of at least one oxidizing agent, at least one
iodide salt or hydroiodic acid, water, at least one organic
solvent, and at least one surfactant. In yet another embodiment,
the leaching composition comprises, consists of, or consists
essentially of at least one oxidizing agent, at least one iodide
salt or hydroiodic acid, water, at least one surfactant, and at
least one metal passivating agent. In yet another embodiment, the
leaching composition comprises, consists of, or consists
essentially of at least one oxidizing agent, at least one iodide
salt or hydroiodic acid, water, at least one organic solvent, at
least one surfactant, and at least one metal passivating agent. It
is understood that the iodide salt or hydroiodic acid and the
oxidizing agent present in the leaching composition will react to
form iodine in situ and iodide ion will be in excess, resulting in
the formation of triiodide. Accordingly, the leaching composition
subsequent to the in situ reaction will comprise, consist of, or
consist essentially of triiodide and water. In another embodiment,
the leaching composition subsequent to the in situ reaction will
comprise, consist of, or consist essentially of triiodide, water,
and at least one organic solvent. In still another embodiment, the
leaching composition subsequent to the in situ reaction will
comprise, consist of, or consist essentially of triiodide, water,
and at least one passivating agent. In still another embodiment,
the leaching composition subsequent to the in situ reaction will
comprise, consist of, or consist essentially of triiodide, water,
and at least one surfactant. In yet another embodiment, the
leaching composition subsequent to the in situ reaction will
comprise, consist of, or consist essentially of triiodide, water,
at least one organic solvent, and at least one passivating agent.
In yet another embodiment, the leaching composition subsequent to
the in situ reaction will comprise, consist of, or consist
essentially of triiodide, water, at least one organic solvent, and
at least one surfactant. In yet another embodiment, the leaching
composition subsequent to the in situ reaction will comprise,
consist of, or consist essentially of triiodide, water, at least
one surfactant, and at least one passivating agent. In yet another
embodiment, the leaching composition subsequent to the in situ
reaction will comprise, consist of, or consist essentially of
triiodide, water, at least one organic solvent, at least one
surfactant, and at least one passivating agent. The leaching
composition is formulated to substantially leach gold from the
e-waste into a fraction that can be further processed to reclaim
said gold. For example, in one embodiment, the leaching composition
can be used to separate gold or other precious from base metals,
wherein the base metals remain as a solid.
[0131] In application, the leaching composition is contacted in any
suitable manner to the e-waste, e.g., by spraying the composition
on the e-waste, by dipping (in a volume of the composition) of the
e-waste, by contacting the e-waste with another material, e.g., a
pad, or fibrous sorbent applicator element, that has the
composition absorbed thereon, or by any other suitable means,
manner or technique, by which a composition is brought into contact
with the e-waste.
[0132] Following the process of contacting the PWBs and/or PWB
components with the leaching composition to leach gold or other
precious metals from the PWBs and/or PWB components, the leaching
composition comprising the gold or other precious metals can be
separated from the PWBs and/or PWB components and precipitates that
may be present. Separation techniques include filtration,
centrifugation, decanting, or a combination of any of these.
[0133] It is to be appreciated by the skilled artisan that
contacting the PWBs and/or PWB components with the leaching
composition to leach gold or other precious metals from the PWBs
and/or PWB components can be done (i) with working leaching
composition until the leaching composition approaches maximum
loading or alternatively, (ii) a "feed and bleed" process may be
used wherein clean leaching composition is periodically introduced
to the working leaching composition with simultaneous withdrawal of
some of the working leaching composition.
[0134] In use of the leaching composition, the composition
typically is contacted with the e-waste for a time of from about 1
minute to about 200 minutes, preferably about 1 min to about 60
min, more preferably about 5 min to about 45 min, at temperature in
a range of from about 20.degree. C. to about 70.degree. C.,
preferably in a range from about 20.degree. C. to about 30.degree.
C. Such contacting times and temperatures are illustrative, and any
other suitable time and temperature conditions may be employed that
are efficacious to separate gold or other precious metals from the
e-waste into a fraction that can be further processed to reclaim
said metal.
[0135] Potential oxidizing agents are defined herein in the second
aspect. Preferably, the oxidizing agent comprises oxone, sodium
persulfate, ammonium persulfate, potassium persulfate, nitric acid,
hydrogen peroxide, ferric chloride, ferric nitrate, or combinations
thereof. Even more preferably, the oxidizing agent comprises
ammonium persulfate, sodium persulfate, nitric acid, periodic acid,
oxone, sodium hypochlorite, or combinations thereof. The amount of
oxidizing agent is in a range from about 0.01 wt % to about 25 wt
%, preferably about 1 wt % to about 20 wt %, and most preferably
about 1 wt % to about 10 wt %.
[0136] Iodide salts include, but are not limited to, lithium
iodide, sodium iodide, potassium iodide, ammonium iodide, calcium
iodide, magnesium iodide, and tetraalkylammonium iodides, wherein
the alkyl groups may be the same as or different from one another
and are selected from the group consisting of straight-chained
C.sub.1-C.sub.6 alkyls (e.g., methyl, ethyl, propyl, butyl, pentyl,
hexyl) and branched C.sub.1-C.sub.6 alkyls. Preferably, the iodide
salt comprises potassium iodide. Hydroiodic acid can be used
instead of an iodide salt. The amount of iodide salt is in a range
from about 0.1 wt % to about 50 wt %, preferably about 1 wt % to
about 40 wt %, and most preferably about 10 wt % to about 35 wt
%.
[0137] Potential organic solvents are defined herein in the second
aspect. Most preferably, the organic solvent comprises an alcohol,
diethylene glycol monobutyl ether, propylene glycol, dipropylene
glycol n-butyl ether, and combinations thereof. When included, the
amount of organic solvent is in a range from about 0.01 wt % to
about 20 wt %, preferably about 1 wt % to about 10 wt %, and most
preferably about 1 wt % to about 5 wt %.
[0138] Potential passivating agents are defined herein in the
second aspect. When included, the amount of passivating agent is in
a range from about 0.01 wt % to about 10 wt %, preferably about
0.05 wt % to about 5 wt %, and most preferably about 0.05 wt % to
about 2 wt %.
[0139] Surfactants contemplated include, but are not limited to,
acids and bases, non-ionic surfactants, anionic surfactants,
cationic surfactants, zwitterionic surfactants, and combinations
thereof. Preferred acidic or basic surfactants include, but are not
limited to, surfactants having an acid or base functionality
("head") and a straight-chained or branched hydrocarbon group
("tail") and/or surfactants having an acid functionality ("head")
and a perfluorinated hydrocarbon group ("tail"). Preferred acid or
base functionalities include phosphoric, phosphonic, phosphonic
monoesters, phosphate monoesters and diesters, carboxylic acids,
dicarboxylic acid monoesters, tricarboxylic acid mono- and
diesters, sulfate monoesters, sulfonic acids, amines, and salts
thereof. The hydrocarbon groups preferably have at least 10, e.g.,
10-20, carbon atoms (e.g., decyl, undecyl, dodecyl, tridecyl,
tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl,
nonadecyl, eicosyl), except that somewhat shorter hydrocarbon
groups of 6-16 carbons (e.g. hexyl, 2-ethylhexyl, dodecyl) are
preferred where the molecule contains two alkyl chains such as in
phosphate diesters and phosphonate monoesters. The perfluorinated
hydrocarbon groups preferably have 7-14 carbon atoms (e.g., heptyl,
octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl).
Preferred surfactants include decylphosphonic acid,
dodecylphosphonic acid, tetradecylphosphonic acid,
hexadecylphosphonic acid, bis(2-ethylhexyl)phosphate,
octadecylphosphonic acid, perfluoroheptanoic acid,
prefluorodecanoic acid, trifluoromethanesulfonic acid,
phosphonoacetic acid, dodecylbenzenesulfonic acid, and
dodecylamine.
[0140] Non-ionic surfactants contemplated include, but are not
limited to, polyoxyethylene lauryl ether (Emalmin NL-100 (Sanyo),
Brij 30, Brij 98), dodecenylsuccinic acid monodiethanol amide
(DSDA, Sanyo), ethylenediamine tetrakis
(ethoxylate-block-propoxylate) tetrol (Tetronic 90R4),
polyoxyethylene polyoxypropylene glycol (Newpole PE-68 (Sanyo),
Pluronic L31, Pluronic 31R1), polyoxypropylene sucrose ether
(SN008S, Sanyo), t-octylphenoxypolyethoxyethanol (Triton X100),
Polyoxyethylene (9) nonylphenylether, branched (IGEPAL CO-250),
polyoxyethylene sorbitol hexaoleate, polyoxyethylene sorbitol
tetraoleate, polyethylene glycol sorbitan monooleate (Tween 80),
sorbitan monooleate (Span 80), alkyl-polyglucoside, ethyl
perfluorobutyrate,
1,1,3,3,5,5-hexamethyl-1,5-bis[2-(5-norbornen-2-yl)ethyl]trisiloxane,
monomeric octadecylsilane derivatives such as SIS6952.0 (Siliclad,
Gelest), siloxane modified polysilazane such as PP1-SG10 Siliclad
Glide 10 (Gelest), silicone-polyether copolymers such as Silwet
L-77 (Setre Chemical Company), Silwet ECO Spreader (Momentive), and
alcohol ethoxylates (Natsurf.TM. 265, Croda).
[0141] Cationic surfactants contemplated include, but are not
limited to, heptadecanefluorooctane sulfonic acid
tetraethylammonium, stearyl trimethylammonium chloride (Econol
TMS-28, Sanyo),
4-(4-diethylaminophenylazo)-1-(4-nitrobenzyl)pyridium bromide,
cetylpyridinium chloride monohydrate, benzalkonium chloride,
benzethonium chloride benzyldimethyldodecylammonium chloride,
benzyldimethylhexadecylammonium chloride,
hexadecyltrimethylammonium bromide, dimethyldioctadecylammonium
chloride, dodecyltrimethylammonium chloride,
hexadecyltrimethylammonium p-toluenesulfonate,
didodecyldimethylammonium bromide, di(hydrogenated
tallow)dimethylammonium chloride, tetraheptylammonium bromide,
tetrakis(decyl)ammonium bromide, Aliquat.RTM. 336 and oxyphenonium
bromide. The hydrocarbon groups preferably have at least 10, e.g.,
10-20, carbon atoms (e.g., decyl, undecyl, dodecyl, tridecyl,
tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl,
nonadecyl, eicosyl), except that somewhat shorter hydrocarbon
groups of 6-20 carbons (e.g. hexyl, 2-ethylhexyl, dodecyl) are
preferred where the molecule contains two functionized alkyl chains
such as in dimethyldioctadecylammonium chloride,
dimethyldihexadecylammonium bromide and di(hydrogenated
tallow)dimethylammonium chloride.
[0142] Anionic surfactants contemplated include, but are not
limited to, sodium polyoxyethylene lauryl ether, sodium
dihexylsulfosuccinate, dicyclohexyl sulfosuccinate sodium salt,
sodium 7-ethyl-2-methyl-4-undecyl sulfate (Tergitol 4), SODOSIL
RM02, and phosphate fluorosurfactants such as Zonyl FSJ.
[0143] Zwitterionic surfactants include, but are not limited to,
ethylene oxide alkylamines (AOA-8, Sanyo), N,N-dimethyldodecylamine
N-oxie, sodium cocaminpropinate (LebonApl-D, Sanyo),
3-(N,N-dimethylmyristylammonio)propanesulfonate, and
(3-(4-heptyl)phenyl-3-hydroxypropyl)dimethylammoniopropanesulfonate.
[0144] Inorganic acids may be optionally added to any of the
leaching compositions. For example, the leaching composition may
further include sulfuric, hydrochloric, hydrobromic, or hydroiodic
acid.
[0145] The pH of the leaching composition is preferably about 3 to
about 10, more preferably about 4 to about 8 and most preferably
about 6 to about 8. In a preferred embodiment, a buffering agent is
added to maintain the pH of the leaching composition in the range
from about 5 to about 8. Buffering agents are well known in the art
and can include, for example, phosphate buffer such as monosodium
phosphate/disodium phosphate or monopotassium phosphate/dipotassium
phosphate.
[0146] In one embodiment, the leaching composition comprises,
consists of, or consists essentially of at least one oxidizing
agent, at least one iodide ion, water, optionally at least one
organic solvent, optionally at least one passivating agent,
optionally at least one surfactant, optionally buffering agent, and
gold or other precious metal ions. Considered after the in situ
reaction, the leaching composition comprises, consists of, or
consists essentially of triiodide, water, optionally at least one
organic solvent, optionally at least one passivating agent,
optionally at least one surfactant, optionally buffering agent, and
gold or other precious metal ions.
[0147] The leaching compositions are easily formulated by simple
addition of the respective ingredients and mixing to homogeneous
condition. Furthermore, the compositions may be readily formulated
as multi-part formulations that are mixed at or before the point of
use, e.g., the individual parts of the multi-part formulation may
be mixed at the tool or in a storage tank upstream of the tool. The
concentrations of the respective ingredients may be widely varied
in specific multiples of the composition, i.e., more dilute or more
concentrated, and it will be appreciated that the compositions can
variously and alternatively comprise, consist or consist
essentially of any combination of ingredients consistent with the
disclosure herein.
[0148] Preferably, in one embodiment, the leaching composition
comprises, consists of, or consists essentially of potassium
iodide, sodium persulfate and water, more preferably about 20 wt %
to about 30 wt % potassium iodide, about 4 wt % to about 10 wt %
sodium persulfate and water. In another embodiment, the leaching
composition comprises, consists of, or consists essentially of
potassium iodide, ammonium persulfate and water, more preferably
about 20 wt % to about 30 wt % potassium iodide, about 4 wt % to
about 10 wt % ammonium persulfate and water. In yet another
embodiment, the leaching composition comprises, consists of, or
consists essentially of potassium iodide, sodium persulfate, BTA,
and water. In yet another embodiment, the leaching composition
comprises, consists of, or consists essentially of potassium
iodide, sodium persulfate, BTA, phosphate buffer, and water. In
still another embodiment, the leaching composition comprises,
consists of, or consists essentially of potassium iodide, nitric
acid and water. In another embodiment, the leaching composition
comprises, consists of, or consists essentially of potassium
iodide, periodic acid, hydrochloric acid and water. The leaching
composition in another embodiment comprises, consists of, or
consists essentially of potassium iodide, oxone and water. In still
another embodiment, the leaching composition comprises, consists
of, or consists essentially of potassium iodide, sodium
hypochlorite, hydrochloric acid and water. In yet another
embodiment, the leaching composition comprises, consists of, or
consists essentially of potassium iodide, in situ generated iodine
and water. The leaching compositions are substantially devoid of
aqua regia and cyanide-containing components. Preferably, the
leaching compositions are water soluble, non-corrosive,
non-flammable and of low toxicity.
[0149] It should be appreciated by the skilled artisan that once
the gold or other precious metals are leached from the PWBs and/or
PWB components, the remaining material(s) may be disposed of,
recycled or undergo further reclamation. Following the
extraction/leaching of the gold or other precious metals into the
leaching composition, the gold or other precious metals can be
obtained by reducing the metal ions, as will be discussed at length
hereinbelow.
[0150] Reduction of the metal ions to solid, high purity metals is
well known to the skilled artisan. Preferably, the reducing agent
is a so-called environmentally friendly chemical. Moreover,
preferably the reduction occurs rapidly with minimal heating
requirements. For example, preferred reducing agents include, but
are not limited to, ascorbic acid, diethyl malonate, sodium
metabisulfite, polyphenon 60 (P60, green tea extract), glucose, and
sodium citrate. For example, as introduced in U.S. Provisional
Patent Application No. 61/375,273 filed on Aug. 20, 2010 and
entitled "Sustainable Process for Reclaiming Precious Metals and
Base Metals from e-Waste," which is hereby incorporated by
reference herein in its entirety, ascorbic acid introduced to a
composition comprising Au.sup.3+ ions at pH 1 produces highly pure
gold metal. Sodium metabisulfite (SMB) can be added to a
composition comprising Au.sup.3+ ions at pH 1 or pH 7 and produce
highly pure gold metal. Alternatively, the gold ions can be
converted to gold metal via electrowinning or electrochemical
techniques. Any suitable means can be used to remove the
precipitated gold. Settling and decanting, filtering the solution
through a filter press or centrifuging are convenient procedures
for such removal.
[0151] In another embodiment, iodide-iodine solution regeneration
is accomplished by (a) decreasing the pH of the solution to below 7
after precipitation of the gold or other precious metals and (b)
adding an oxidizing agent to the solution. After repeated
regenerations if any interfering salt buildup decreases the
effectiveness of the solution all iodine can be recovered as
elemental iodine by precipitation from solution by acidifying and
adding an oxidizing agent. The resulting elemental iodine crystals
can be removed and used to form a new leaching composition.
Method of Processing Bare Boards
[0152] Following the removal of PWB components (e.g., as described
in the method of the first aspect) and precious metals (e.g., as
described in the method of the third or fifth aspect), the original
PWB has typically been stripped to a "bare board" comprising a
fiberglass layer and a copper sheet that are held together by an
adhesive such as epoxy. The bare board can be further processed to
liberate the fiberglass-epoxy layer from the copper.
[0153] In one embodiment of the sixth aspect, the bare board can be
processed by degrading the epoxy, which liberates the copper sheet
from the fiberglass. The epoxy can be degraded using a composition
that chemically degrades the epoxy, as readily determined by one
skilled in the art. Ultrasonics or other agitation means can be
used in the liberation of the copper sheet from the fiberglass.
[0154] In another embodiment of the sixth aspect, the bare board
can be processed by a process of wet grinding the bare board in a
copper etchant. The solution produced will comprise a solid powder
in a copper-containing solution, which can be physically separated
from one another using methods known in the art (e.g.,
centrifugation, decanting, filtering, etc.). The copper etchant can
be the composition of the fourth aspect described herein or
alternatively, sulfuric acid aerated with oxygen or ozone or
H.sub.2O.sub.2 or any other solution capable of dissolving metallic
copper without affecting fiberglass and epoxy. The solid powder,
which comprises the fiberglass and epoxy can be further processed
to degrade the epoxy to liberate the fiberglass powder for reuse.
The copper-containing solution, e.g., copper sulfate, can be sold
as is or further processed to liberate copper metal therefrom
(e.g., electrowinning, etc.).
Methods of Recycling Printed Wire Boards
[0155] One embodiment of seventh aspect corresponds to a process of
removing at least one component from a surface, e.g., a PWB, as
generalized in FIG. 1, said method comprising:
(a) the method of the first aspect; and (b) the method of the third
aspect, or (a) removing solder from the surface, wherein the
removal of solder releases at least one component from the surface;
and (b) removing base metals from the surface, thereby undercutting
the precious metals from the surface, or (a) removing solder from
the surface, wherein the removal of solder releases at least one
component from the surface; and (b) contacting said surface with a
second composition in a vessel, and optionally producing ultrasonic
cavitation or other agitation means in said vessel, to selectively
remove base metals relative to the precious metals present on said
surface thereby undercutting the precious metals from the surface,
or (a) contacting solder with a first composition in a vessel, and
optionally producing ultrasonic cavitation or other agitation means
in said vessel, to selectively remove the solder relative to
precious metals, tantalum-containing metals, and/or base metals
that are simultaneously present on said surface, wherein the
removal of solder releases at least one component from the surface;
and (b) removing base metals from the surface, thereby undercutting
the precious metals from the surface, or (a) contacting solder with
a first composition in a vessel, and optionally producing
ultrasonic cavitation or other agitation means in said vessel, to
selectively remove the solder relative to precious metals,
tantalum-containing metals, and/or base metals that are
simultaneously present on said surface, wherein the removal of
solder releases at least one component from the surface; and (b)
contacting said surface with a second composition in a vessel, and
optionally producing ultrasonic cavitation or other agitation means
in said vessel, to selectively remove base metals relative to the
precious metals present on said surface thereby undercutting the
precious metals from the surface.
[0156] A second embodiment of seventh aspect corresponds to a
process of removing at least one component from a surface e.g., a
PWB, as generalized in FIG. 2, said method comprising:
(a) the method of the first aspect; (b) the method of the third
aspect; and (c) the method of the sixth aspect, or (a) removing
solder from the surface, wherein the removal of solder releases at
least one component from the surface; (b) removing base metals from
the surface, thereby undercutting the precious metals from the
surface to yield a bare board comprising fiberglass and copper; and
(c) separating the fiberglass and copper of the bare board, or (a)
removing solder from the surface, wherein the removal of solder
releases at least one component from the surface; (b) contacting
said surface with a second composition in a vessel, and optionally
producing ultrasonic cavitation or other agitation means in said
vessel, to selectively remove base metals relative to the precious
metals present on said surface thereby undercutting the precious
metals from the surface, to yield a bare board comprising
fiberglass and copper; and (c) separating the fiberglass and copper
of the bare board, or (a) contacting solder with a first
composition in a vessel, and optionally producing ultrasonic
cavitation or other agitation means in said vessel, to selectively
remove the solder relative to precious metals, tantalum-containing
metals, and/or base metals that are simultaneously present on said
surface, wherein at least one component is released from the
surface when the solder is removed, wherein the removal of solder
releases at least one component from the surface; (b) removing base
metals from the surface, thereby undercutting the precious metals
from the surface, to yield a bare board comprising fiberglass layer
and copper; and (c) separating the fiberglass layer and copper of
the bare board, or (a) contacting solder with a first composition
in a vessel, and optionally producing ultrasonic cavitation or
other agitation means in said vessel, to selectively remove the
solder relative to precious metals, tantalum-containing metals,
and/or base metals that are simultaneously present on said surface,
wherein at least one component is released from the surface when
the solder is removed, wherein the removal of solder releases at
least one component from the surface; (b) contacting said surface
with a second composition in a vessel, and optionally producing
ultrasonic cavitation or other agitation means in said vessel, to
selectively remove base metals relative to the precious metals
present on said surface thereby undercutting the precious metals
from the surface, to yield a bare board comprising fiberglass layer
and copper; and (c) separating the fiberglass layer and copper of
the bare board.
[0157] A third embodiment of seventh aspect corresponds to a
process of removing at least one component from a surface e.g., a
PWB, as generalized in FIG. 3, said method comprising:
(a) the method of the third aspect; and (b) the method of the sixth
aspect, or (a) removing base metals from the surface, thereby
undercutting the precious metals from the surface, to yield a bare
board comprising fiberglass layer and copper; (b) separating the
fiberglass material and copper of the bare board, or (a) contacting
said surface with a second composition in a vessel, and optionally
producing ultrasonic cavitation or other agitation means in said
vessel, to selectively remove base metals relative to the precious
metals present on said surface thereby undercutting the precious
metals from the surface, to yield a bare board comprising
fiberglass and copper; (b) separating the fiberglass material and
copper of the bare board.
[0158] A fourth embodiment of eighth aspect corresponds to a
process of removing at least one component from a surface, e.g., a
PWB, as generalized in FIG. 4, said method comprising:
(a) the method of the first aspect; and (b) a method of the fifth
aspect, or (a) removing solder from the surface, wherein the
removal of solder releases at least one component from the surface;
and (b) leaching precious metals from said surface and/or said at
least one component, or (a) removing solder from the surface,
wherein the removal of solder releases at least one component from
the surface; and (b) introducing the surface and/or at least one
component to a leaching composition in a vessel, and optionally
producing ultrasonic cavitation or other agitation means in said
vessel, wherein said leaching composition comprises triiodide, to
substantially remove precious metals from said surface and/or said
at least one component, or (a) contacting solder with a first
composition in a vessel, and optionally producing ultrasonic
cavitation or other agitation means in said vessel, to selectively
remove the solder relative to precious metals, tantalum-containing
metals, and/or base metals that are simultaneously present on said
surface, wherein the removal of solder releases at least one
component from the surface; and (b) leaching precious metals from
said surface and/or said at least one component, or (a) contacting
solder with a first composition in a vessel, and optionally
producing ultrasonic cavitation or other agitation means in said
vessel, to selectively remove the solder relative to precious
metals, tantalum-containing metals, and/or base metals that are
simultaneously present on said surface, wherein the removal of
solder releases at least one component from the surface; and (b)
introducing the surface and/or said at least one component to a
leaching composition in a vessel, and optionally producing
ultrasonic cavitation or other agitation means in said vessel,
wherein said leaching composition comprises triiodide, to
substantially remove precious metals from said surface and/or said
at least one component.
[0159] A fifth embodiment of seventh aspect corresponds to a
process of removing at least one component from a surface, e.g., a
PWB, as generalized in FIG. 5, said method comprising:
(a) the method of the first aspect; (b) the method of the fifth
aspect; and (c) the method of the sixth aspect, or (a) removing
solder from the surface, wherein the removal of solder releases at
least one component from the surface; (b) leaching precious metals
from said surface to yield a bare board comprising fiberglass layer
and copper; and (c) separating the fiberglass layer and copper of
the bare board, or (a) removing solder from the surface, wherein
the removal of solder releases at least one component from the
surface; (b) introducing the surface to a leaching composition in a
vessel, and optionally producing ultrasonic cavitation or other
agitation means in said vessel, wherein said leaching composition
comprises triiodide, to substantially remove precious metals from
said surface, to yield a bare board comprising fiberglass layer and
copper; and (c) separating the fiberglass layer and copper of the
bare board, or (a) contacting solder with a first composition in a
vessel, and optionally producing ultrasonic cavitation or other
agitation means in said vessel, to selectively remove the solder
relative to precious metals, tantalum-containing metals, and/or
base metals that are simultaneously present on said surface,
wherein the removal of solder releases at least one component from
the surface; (b) leaching precious metals from said surface to
yield a bare board comprising fiberglass layer and copper; and (c)
separating the fiberglass layer and copper of the bare board, or
(a) contacting solder with a first composition in a vessel, and
optionally producing ultrasonic cavitation or other agitation means
in said vessel, to selectively remove the solder relative to
precious metals, tantalum-containing metals, and/or base metals
that are simultaneously present on said surface, wherein the
removal of solder releases at least one component from the surface;
(b) introducing the surface to a leaching composition in a vessel,
and optionally producing ultrasonic cavitation or other agitation
means in said vessel, wherein said leaching composition comprises
triiodide, to substantially remove precious metals from said
surface, to yield a bare board comprising fiberglass layer and
copper; and (c) separating the fiberglass layer and copper of the
bare board.
[0160] Regardless of which embodiment of the seventh aspect is
used, consistent with the disclosures herein, the solder can
comprise lead, tin, or a combination of lead and tin. Preferably,
the surface includes a PWB and the recyclable material comprises
components (e.g., ICs), precious metals, base metals, or any
combination of components, precious metals and base metals. The
released components can be collected and can be separated into
those that are reusable and can be resold and those that can be
further processed for disposal, reclamation of useful materials,
etc. The first composition preferably selectively removes solder
(e.g., lead, tin, alloys thereof, and combinations thereof)
relative to precious metals, tantalum-containing metals, and/or
base metals, and the components that are liberated following
removal of the solder are readily collected and sorted for reuse or
reclamation purposes. The second composition preferably etchingly
removes the base metals such as copper and/or nickel and undercuts
the precious metals (e.g., gold), wherein the precious metals
delaminate from the surface and is readily collected (e.g., by
filtering). Subsequent to solder removal, the first composition,
which includes lead and/or tin ions, can be subjected to further
processing (e.g., electrowinning) to reclaim the lead and/or tin.
Subsequent to base metal removal, the second composition comprising
the base metal ions can be processed to obtain useful forms of said
base metals (e.g., electrochemically or by electrowinning). Methods
of separating the fiberglass and copper of the bare board are
disclosed in the sixth aspect herein. Preferably, prior to
introducing the at least one PWB component or the surface to the
leaching composition, the at least one PWB component or surface is
crushed. Subsequent to leaching, the gold can be precipitated as
described herein. Although not wishing to be bound by theory, it is
thought that the ultrasonics or other agitation means in the
presence of the first, second and/or leaching compositions enhance
the selective leaching of the materials to be removed. Ultrasonics
or other agitation means may be applied exclusively in the presence
of the first composition, exclusively in the presence of the second
composition, exclusively in the presence of the leaching
composition, any combination of the three, or not at all. It should
be appreciated by the skilled artisan that the compositions of the
second and fourth aspect described herein represent just one
version of the first and second compositions, respectively, of the
seventh aspect. Other first and second compositions are
contemplated for use in the process of the seventh aspect, as
readily determined by one skilled in the art. It should be
appreciated that rinsing and/or drying steps are contemplated
following the contact of the first, second and/or leaching
compositions with the PWB. The conditions of contact (i.e., time
and temperature) were introduced herein. Advantageously, the method
allows a user to take obsolete and used printed wire boards and
recycle the electronic components and metals contained thereon for
reuse.
[0161] An eighth aspect relates to a kit including, in one or more
containers, one or more species adapted to form the compositions
described herein.
[0162] In a ninth aspect, a method of removing lead and/or
tin-containing materials from a solid material is described,
wherein said method includes contacting the first composition with
the solid material having the lead and/or tin-containing materials
thereon or therein, under sufficient contacting conditions to
remove the lead and/or tin-containing materials from the solid
material. The solid material includes, but is not limited to,
microelectronic devices, metals, plastics, fabrics, fibers, soils,
ores, wood, paper, glass, leather and other animal hides, cement,
concrete, bricks, drywall, asphalt, keratin-containing substances
such as hair and nails, rubber, latex, and combinations thereof.
For example, in one embodiment, lead and/or tin-containing
materials may be removed from soil to remediate same.
[0163] In a tenth aspect, a method of removing copper and/or
nickel-containing materials from a solid material is described,
wherein said method includes contacting the second composition with
the solid material having the copper and/or nickel-containing
materials thereon or therein, under sufficient contacting
conditions to remove the copper and/or nickel-containing materials
from the solid material. The solid material includes, but is not
limited to, microelectronic devices, metals, plastics, fabrics,
fibers, soils, ores, wood, paper, glass, leather and other animal
hides, cement, concrete, bricks, drywall, asphalt,
keratin-containing substances such as hair and nails, rubber,
latex, and combinations thereof. For example, in one embodiment,
lead and/or tin-containing materials may be removed from ores
containing same.
[0164] Advantageously, the methods and compositions described
herein provide environmentally-friendly solutions to recycling
printed wire boards, with high percentages of the recyclable
materials able to be reclaimed for reuse.
[0165] The features and advantages of the invention are more fully
shown by the illustrative examples discussed below.
Example 1
[0166] Three compositions were prepared, a 1:1 v/v HEDP/30 wt %
H.sub.2O.sub.2 solution (formulation A), a 1:1 v/v EDDS/30 wt %
H.sub.2O.sub.2 solution (formulation B), and a 1:1 v/v HEIDA/30 wt
% H.sub.2O.sub.2 solution (formulation C). Approximately 0.3 g of
copper wire, nickel foil, granular tin, lead foil, aluminum wire,
iron powder and granular zinc were individually and statically
immersed in clean formulations A-C at 40.degree. C. for 30 minutes.
Following removal of the remaining solids, the solutions were
subjected to inductively coupled plasma (ICP) analysis to determine
the concentration of each metal (in ppm) in each solution. The
results are summarized in Tables 1-3.
TABLE-US-00001 TABLE 1 Results following immersion of materials in
Formulation A. Sample to Al/ Cu/ Fe/ Ni/ Pb/ Sn/ Zn/ Chemistry be
Tested pH ppm ppm ppm ppm ppm ppm ppm HEDP/H.sub.2O.sub.2 NA 1 ND
1.81 0.07 0.16 ND 0.16 0.28 HEDP/H.sub.2O.sub.2 Copper wire 1 0.43
14770 30.11 0.38 4.23 1.96 39.93 HEDP/H.sub.2O.sub.2 Nickel Foil 1
0.3 3.1 0.08 10.45 ND ND 0.26 HEDP/H.sub.2O.sub.2 Tin Granular 1
0.11 1.44 0.17 0.12 ND ND 0.19 HEDP/H.sub.2O.sub.2 Lead Foil 1 0.66
3.19 0.11 0.13 56.8 ND 0.23 HEDP/H.sub.2O.sub.2 Al wire 1 12.2 2.09
0.14 ND ND ND 0.19 HEDP/H.sub.2O.sub.2 Fe powder 1 0.12 5.44 7439
0.15 ND ND 2.16 HEDP/H.sub.2O.sub.2 Zn granular 1 ND 2.54 0.08 0.09
ND ND 0.17
TABLE-US-00002 TABLE 2 Results following immersion of materials in
Formulation B. Sample to be Al/ Cu/ Fe/ Ni/ Pb/ Sn/ Zn/ Chemistry
Tested pH ppm ppm ppm ppm ppm ppm ppm HEIDA/H.sub.2O.sub.2 Copper
wire 2 ND 1231 ND ND 1.89 ND 3.5 HEIDA/H.sub.2O.sub.2 Nickel Foil 2
ND 2.06 0.16 0.34 3.07 ND 0.07 HEIDA/H.sub.2O.sub.2 Tin Granular 2
ND ND ND ND 0.52 ND 0.07 HEIDA/H.sub.2O.sub.2 Lead Foil 2 ND 1.65
ND ND 7320 ND 0.09 HEIDA/H.sub.2O.sub.2 Al wire 2 ND 2.54 0.1 ND ND
ND 0.02 HEIDA/H.sub.2O.sub.2 Fe powder 2 ND ND 1.5 ND ND ND 615
HEIDA/H.sub.2O.sub.2 Zn granular 2 ND 6.44 ND ND ND ND 0.01
TABLE-US-00003 TABLE 3 Results following immersion of materials in
Formulation C. Sample to be Al/ Cu/ Fe/ Ni/ Pb/ Sn/ Zn/ Chemistry
Tested pH ppm ppm ppm ppm ppm ppm ppm EDDS/H.sub.2O.sub.2 copper
wire 6 ND 157 1.86 0.12 ND 0.18 0.47 EDDS/H.sub.2O.sub.2 Nickel
Foil 6 ND ND 1.38 0.15 ND ND 0.09 EDDS/H.sub.2O.sub.2 Tin Granular
6 ND 0.58 1.62 5.62 0.33 0.25 0.16 EDDS/H.sub.2O.sub.2 Lead Foil 6
ND ND 0.21 ND 1565 ND 0.13 EDDS/H.sub.2O.sub.2 Al wire 6 1.32 ND
0.98 ND 0.07 0.28 0.21 EDDS/H.sub.2O.sub.2 Fe powder 6 0.09 0.16
8.47 ND ND 0.97 215 EDDS/H.sub.2O.sub.2 Zn granular 6 ND ND 0.25 ND
ND 0.16 0.09
[0167] It can be seen that the compositions comprising HEIDA or
EDDS are especially useful for removing lead relative to copper and
other precious metals, especially if the user optionally considers
including a copper passivating agent in both compositions.
Example 2
[0168] Compositions were prepared as described in Table 4 below.
Copper wire, lead foil, granular tin, nickel foil, aluminum wire,
iron powder and granular zinc were individually and statically
immersed in each formulations at 40.degree. C. for 30 minutes.
Following removal of the remaining solids, the solutions were
subjected to inductively coupled plasma (ICP) analysis to determine
the concentration of each metal (in ppm) in each solution. The
results are summarized in Table 4.
TABLE-US-00004 TABLE 4 Results following immersion of materials in
the listed compositions. Al/ Cu/ Fe/ Ni/ Pb/ Sn/ Zn/ Chemistry ppm
ppm ppm ppm ppm ppm ppm First composition (remove Pb/Sn
selectively) MSA 4940 ND 109300 1861 1040 2453 236 MSA + 1 wt %
butyl carbitol (BC) 45 ND 1531000 74 52200 4217 3324 MSA + 1 wt %
BC + 0.3 wt % sodium 69.6 24.8 63920 8.4 23720 13840 293.6
molybdate dihydrate MSA + 1 wt % BC + 0.3 wt % suberic acid ND ND
794400 21.6 16400 2420 625.2 Second composition (remove Cu/Ni
selectively) oxone (10 wt % in water) 56.8 3030 15560 0.8 2.1 ND
9630 oxone (10 wt % in water) + 0.3 wt % suberic 67.46 7220 1574.6
24.6 4.6 ND 17500 acid oxone (10 wt % in water) + 0.3 wt % sodium
70.6 9820 217 30.8 ND 53.6 5240 molybdate dihydrate oxone (10 wt %
in water) + 0.3 wt % sodium 22.8 14040 1420 20.6 ND ND 17500
hexametaphosphate potassium persulfate (5 wt % in water) 14 215.9
64500 4.4 3.3 ND 5420 5 wt % ammonium persulfate 24.6 374 96480
13.8 277.6 ND 14560 30 wt % ammonium persulfate 102.2 11360 202600
24.4 293.4 ND 49620
[0169] Surprisingly, when butyl carbitol and sodium molybdate was
added to MSA to produce the first composition, the etch rates of Pb
and Sn significantly increased while the etch rates of Al, Fe, Ni
and Zn significantly decreased. Accordingly, the first composition
including MSA, butyl carbitol and sodium molybdate dihydrate will
be useful for the selective removal of Pb/Sn containing solder
relative to precious metals and/or copper.
[0170] When sodium molybdate or sodium hexametaphosphate were added
to oxone to produce the second composition, the etch rates of Cu
increased significantly while the etch rates of Fe decreased
significantly. Accordingly, the second composition including oxone
and sodium molybdate or sodium hexametaphosphate will be useful for
the selective removal of Cu relative to other metals.
Example 3
[0171] An aqueous first composition was prepared, containing 250 mL
of 70% methane sulfonic acid and 250 mL of deionized (DI) water. A
waste video card NVIDIA model P118 was immersed in the first
composition in silent leaching mode. The mounted components were
detached in 4 days, gold plating was not affected, some pins on the
detached components corroded, sludge and gas formation were not
detected. The same solution was irradiated by ultrasound during 30
minutes but gave no noticeable result in detaching components.
[0172] An imitation of commercially available nitric acid based
solder stripping solution was prepared, containing 145 mL of 70%
nitric acid, 30 g of ammonium sulfamate, 1 g of benzotriazole and
40 g of ferric nitrate nonahydrate, balanced by DI water to 500 mL
of total volume. A video card was subjected to silent leaching in
this solution. The components detached in 20 minutes, the solution
became green and a piece of steel, which is part of the video card,
almost completely dissolved, which proves that commercially
available solder solutions cannot be used to achieve the goals of
the present invention.
[0173] A first composition containing 200 mL of 70% MSA, 50 mL of
70% nitric acid, 30 g of ammonium sulfamate and 1 g of
benzotriazole, balanced by DI water to 500 mL of total volume was
prepared and a video card was immersed in the first composition in
silent leaching mode. The components started to detach in 45
minutes, all the components were detached in one hour. No sludge
and gas formation was noticed, gold plating was not affected, and
the components' pins were not damaged by corrosion.
[0174] A first composition containing 200 mL of 70% MSA, 50 mL of
70% nitric acid, 8 g of ammonium sulfamate, 1 g of benzotriazole
and balanced by DI water to the volume of 500 mL was prepared. The
first composition was poured into a 750-mL leaching container, a
video card was immersed in the solution and the container was
closed with a cover, which had an opening left for the ultrasonic
horn to be inserted. A 1000 W ultrasonic processor with operational
frequency 20 kHz, frontal area of 9.0 cm.sup.2 and amplitude ratio
approx. 1:2.4 was used to create ultrasonic irradiation (UIP1000 hd
manufactured by Hielscher Ultrasonics GmbH). A mechanical amplitude
booster was used for amplitude increase with ratio 1:1.8. The
combination of such a sonotrode with such a booster provided the
maximal amplitude of 35 .mu.m at 100% amplitude setting. The
ultrasonic horn was immersed in the first composition and was
positioned in such a way so as not to touch the surface of the
board or the components. The application of ultrasound irradiation
created strong cavitation in the volume of first composition,
visible as intense cavitation bubbles. After six minutes of
sonication with amplitude of 100%, some components detached from
the surface of the board; after two additional minutes all the
components detached. No sludge or gas formation was noticed, gold
plating was not affected, and components' pins were not damaged by
corrosion. The same results were obtained with a RAM stick, model
128 Mbytes from SEC and a network card from 3Com model
920-ST03.
Example 4
Compositions A and B were Formulated
[0175] Composition A: 10 g KI, 2.5 g sodium persulfate, 25 mL water
Composition B: 10 g KI, 2.5 g ammonium persulfate, 25 mL water
[0176] Printed wire boards (less than 2 cm.times.2 cm) coated with
about 0.05%-0.5% gold were immersed in Compositions A and B at room
temperature and the extent of gold dissolution monitored at 4
minutes, 10 minutes and 30 minutes using Inductively Coupled Plasma
(ICP-OES) spectroscopy. In composition A, 80% of the gold was
dissolved within 4 min, and 99% within 10 min. In composition B,
90% of the gold was dissolved within 4 min, and 100% within 10
min.
Example 5
Compositions C-G were Formulated
[0177] Composition C: 40.08 g KI, 10.03 g I.sub.2, 100 g water
Composition D: 40 g KI, 10.02 g HNO.sub.3 (70%), 100 g water
Composition E: 40.08 g KI, 9.98 g HIO.sub.4, 10.04 g HCl (37%),
90.08 g water Composition F: 39.99 g KI, 10.00 g oxone, 100.04 g
water Composition G: 40.10 g KI, 9.99 g NaOCl, 10.06 g HCl (37%),
89.96 g water
[0178] Compositions C-G are all deep red after mixing, with
compositions E and F having some precipitate in the container.
Printed wire boards (less than 2 cm.times.2 cm) coated with about
0.05%-0.5% gold were immersed in approximately 50 g of Compositions
C-G (a) in a water bath maintained at 39.degree. C. for 30 min. The
results are tabulated in Table 5.
TABLE-US-00005 TABLE 5 Extent of Au dissolution in Compositions
C-G. Formulation water bath results C 10 min, 70% Au dissolved 20
min, 100% Au dissolved D 10 min, no change 20 min, no change 30
min, no change E 10 min, 100% Au dissolved F 10 min, 75% Au
dissolved ~15 min, 100% Au dissolved G 10 min, 5% Au dissolved 20
min, 50% Au dissolved ~25 min, 85% Au dissolved ~30 min, 100% Au
dissolved
Example 6
[0179] Leaching rate, bath loading and bath life was compared for
solutions containing (a) KI, sodium persulfate, and water, (b) KI,
ammonium persulfate, and water, and (c) KI, oxone, and water,
wherein the amounts of iodide salt, oxidizing agent and water in
each solution are the same. Printed wire boards (less than 2
cm.times.2 cm) coated with about 0.05%.about.0.5% gold were
immersed in each composition at room temperature and the extent of
gold dissolution monitored at 30 minutes using ICP-OES. Loading
results are shown in Table 6 for several metals.
TABLE-US-00006 TABLE 6 Metals loading in compositions at room
temperature. KI, sodium KI, ammonium persulfate, persulfate, KI,
oxone, and water and water and water Metal .mu.g/mL Ag 0.14 0.09
0.42 Al 0.092 Au 281.42 250.47 214.44 Co 0.031 0.02 0.013 Cu 19.3
23.15 28.2 Fe 0.15 Ni 10.89 9.64 15.07 Pb 3.3 3.06 2.21 Sn 0.37
0.33 0.44 Zn 24.46 25.69 0.17
[0180] Further, it was concluded that the solution containing the
ammonium persulfate had the least deposition formation while the
solution containing the oxone had the lowest leaching rate, lowest
loading, lowest bath life, and highest amount of deposition.
[0181] It was further discovered that the deposit and the PWB's can
be rinsed and the rinse water collected to maximize the recovery of
gold from the solution.
Example 7
[0182] Printed wire board pieces were immersed in Composition F at
room temperature and 40.degree. C. and the extent of metal
dissolution monitored at intervals using ICP-OES. Each sample was
diluted 50 times with water prior to analysis. The results are
tabulated in Table 7.
TABLE-US-00007 TABLE 7 Metals loading in Composition F at room
temperature and 40.degree. C. 40.degree. C., room temperature, 50 g
Composition F, 36 g Composition F, 21 pieces PWB 27 pieces PWB
Metal .mu.g/mL Ag 0.012 0.014 Au 160.99 676.97 Co 0.008 0.014 Cu
4.91 5.39 Ni 4.38 9.14 Pb 0.11 0.088 Sn 0.13
[0183] It can be seen that the formulations are actually more
effective at leaching metals at room temperature than they are at
elevated temperatures.
Example 8
[0184] Pieces of bare printed circuit boards with visible gold
plating and total weight of 380 g were placed in a 2-litre glass
beaker, to which 1 litre of an aqueous solution of potassium iodide
was added (72.5 g of solid potassium iodide per 100 mL of
de-ionized water). The experiment was held at the ambient
temperature of 21.degree. C. The sonotrode of the ultrasound device
UIP1000 hd (20 kHz, 1000 W, manufactured by Hielscher Ultrasonics
GmbH) was placed into the beaker and was positioned in such a way
to be immersed in the solution and not to touch the PWBs. The
ultrasonic device was operated with the ultrasonic frequency of 20
kHz and amplitude of 25 microns for 2 minutes, after which the
ultrasonic horn was removed from the beaker. The application of
ultrasound irradiation to the solution volume created strong
cavitation, visible as intense cavitation bubbles formed in the
volume of the liquid. The solution changed its color from clear to
tea-brown, which indicated formation of tri-iodide ions. 1 mL of
70% nitric acid was added to the solution. No visible remaining
gold plating was detected by visual inspection on the surface of
treated boards; at the same time the base metals were not affected.
The pieces of boards were removed from the beaker, and the solution
was filtered through an 1810 Whatman Acid-Treated Low Metal TCLP
filter to remove any solid impurities. The pregnant solution was
then mixed with a saturated aqueous solution of sodium bisulfite
and stirred with a mechanical mixer for 30 minutes. The solution
changed its color to clear yellow, and a fine brown powder of
metallic gold precipitated. The powder was filtered off, rinsed
with deionized water and dried. Separate analysis of the recovered
precipitate showed 99.2.+-.0.2% gold. The precipitate was heated in
a porcelain crucible at 1200.degree. C. whereby a metallic gold
button was formed.
[0185] The analysis of liquid showed 2 ppm gold in the spent
solution. To restore the leaching solution, it was oxidized back to
its original strength by the slow addition of 30% hydrogen peroxide
with stirring until the solution regained its tea-brown color.
[0186] The processed PWBs were rinsed with 500 mL of water and
dried. The rinse water containing low concentration of tri-iodide
solution was treated with an excess of the saturated solution of
potassium persulfate, whereby the crystal iodine appeared in the
volume of the liquid as black powder precipitate and the rinse
water lost its slight tea-color, becoming colorless. The iodine was
separated from the solution and dissolved in the regenerated
leaching solution.
Example 9
[0187] 200 g of a "red metals" concentrate, which was created as a
result of mechanical recycling of waste electronic equipment, was
treated with the same leaching composition as described in Example
8, buffered with potassium dihydrogen phosphate/sodium hydroxide to
pH=5.6. The concentrate represents an output material of a
shredding and grinding operation applied to mixed electronic waste,
followed by magnetic and eddy-current separation and concentration
on shaker tables. The composition of the initial metallic mixture
with particle size 0.4-1 mm is shown in Table 8.
TABLE-US-00008 TABLE 8 Composition of non-treated concentrate
measured in "Electronic Alloys" mode with Niton XL3t GOLDD
XRF-Analyzer manufactured by Thermo Fisher Scientific Inc. element
Ag Au Pt Pb Zn Cu Fe Sn others % 0.158 1.564 0.395 15.615 10.794
52.766 6.015 9.813 2.880
[0188] The "red metals" concentrate was brought in contact with 1
litre of leaching composition in a 2-litre beaker under ultrasonic
irradiation of 20 kHz leaching solution and amplitude of 25 microns
for 2 minutes. The metallic mixture was separated from the pregnant
leach liqueur by filtering, washed with deionized water and dried.
Measurement of the concentration of metals in the treated sample
showed non-detectable levels of Ag, Au, Pt and Pd.
[0189] The precious metals in the filtrate were recovered by
dripping 10 mL of stabilized sodium borohydride (4.4 M in 14M NaOH)
into the leach liqueur and stirring, whereby the powdered
precipitate of precious metals appeared in the solution. 30 mL of
MAGNAFLOC-351 flocculating agent was added to the liquid-solid
mixture, and the powdered particles adhered to the granules. The
liquid was filtered and the precipitate of mixed precious metals
was recovered, washed and dried. The precipitate was heated in the
inductive furnace to 1850.degree. C., forming an alloy of precious
metals. The leaching solution was brought back to its original
strength by dripping 30% hydrogen peroxide into the solution until
the tea-brown color of the solution was restored.
[0190] Although the invention has been variously disclosed herein
with reference to illustrative embodiments and features, it will be
appreciated that the embodiments and features described hereinabove
are not intended to limit the invention, and that other variations,
modifications and other embodiments will suggest themselves to
those of ordinary skill in the art, based on the disclosure herein.
The invention therefore is to be broadly construed, as encompassing
all such variations, modifications and alternative embodiments
within the spirit and scope of the claims hereafter set forth.
* * * * *