U.S. patent application number 14/993614 was filed with the patent office on 2016-05-05 for sustainable process for reclaiming precious metals and base metals from e-waste.
The applicant listed for this patent is ADVANCED TECHNOLOGY MATERIALS, INC.. Invention is credited to Dinakar GNANAMGARI, Laura INGALLS, Ping JIANG, Michael B. KORZENSKI, Ted MENDUM, James NORMAN, Fred STRICKLER, John WARNER.
Application Number | 20160122846 14/993614 |
Document ID | / |
Family ID | 45605692 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160122846 |
Kind Code |
A1 |
KORZENSKI; Michael B. ; et
al. |
May 5, 2016 |
SUSTAINABLE PROCESS FOR RECLAIMING PRECIOUS METALS AND BASE METALS
FROM E-WASTE
Abstract
Processes for recycling electronic components removed from
printed wire boards, whereby precious metals and base metals are
extracted from the electronic components using environmentally
friendly compositions. At least gold, silver and copper ions can be
extracted from the electronic components and reduced to their
respective metals using the processes and compositions described
herein.
Inventors: |
KORZENSKI; Michael B.;
(Bethel, CT) ; JIANG; Ping; (Danbury, CT) ;
NORMAN; James; (Wilmington, MA) ; WARNER; John;
(Wilmington, MA) ; INGALLS; Laura; (Wilmington,
MA) ; GNANAMGARI; Dinakar; (Wilmington, MA) ;
STRICKLER; Fred; (Wilmington, MA) ; MENDUM; Ted;
(Wilmington, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ADVANCED TECHNOLOGY MATERIALS, INC. |
DANBURY |
CT |
US |
|
|
Family ID: |
45605692 |
Appl. No.: |
14/993614 |
Filed: |
January 12, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13817868 |
Aug 28, 2013 |
9238850 |
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PCT/US2011/048449 |
Aug 19, 2011 |
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14993614 |
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61375273 |
Aug 20, 2010 |
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Current U.S.
Class: |
75/744 |
Current CPC
Class: |
C22B 7/007 20130101;
C22B 3/16 20130101; C22B 15/0067 20130101; Y02P 10/234 20151101;
Y02P 10/214 20151101; C22B 15/0071 20130101; Y02P 10/20 20151101;
C22B 7/008 20130101; C22B 15/0006 20130101; C22B 3/0005 20130101;
C22B 15/0078 20130101; C22B 15/0069 20130101; C22B 7/006 20130101;
C22B 11/046 20130101; C22B 15/0073 20130101; C22B 1/005 20130101;
Y02W 30/50 20150501 |
International
Class: |
C22B 3/00 20060101
C22B003/00; C22B 3/16 20060101 C22B003/16; C22B 7/00 20060101
C22B007/00; C22B 15/00 20060101 C22B015/00; C22B 1/00 20060101
C22B001/00 |
Claims
1.-30. (canceled)
31. A method of removing more than one metal from e-waste, said
method comprising: (a) contacting the e-waste with a first metal
digestion composition to form a first extraction liquid and a first
extraction solid, wherein the first metal digestion composition
comprises at least one oxidizing agent and at least one complexing
agent; (b) separating the first extraction solid from the first
extraction liquid; (c) contacting the first extraction solid with a
second metal digestion composition to form a second extraction
liquid and a second extraction solid, wherein the second metal
digestion composition comprises at least one oxidizing agent and at
least one complexing agent; (d) separating the second extraction
solid from the second extraction liquid, wherein the second
extraction liquid comprises first metal ions; and (e) contacting
the first extraction liquid with an additive to separate second
metal ions from third metal ions, wherein the at least one
oxidizing agent comprises methanesulfonic acid (MSA),
ethanesulfonic acid, benzenesulfonic acid, 2-hydroxyethanesulfonic
acid, cyclohexylaminosulfonic acid, n-propanesulfonic acid,
n-butanesulfonic acid, or n-octanesulfonic acid, hydrogen peroxide
(H.sub.2O.sub.2), FeCl.sub.3 (both hydrated and unhydrated), oxone
(2KHSO.sub.5.KHSO.sub.4.K.sub.2SO.sub.4), 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 persulfate
(Na.sub.2S.sub.2O.sub.8), sodium hypochlorite (NaClO), potassium
iodate (KIO.sub.3), potassium permanganate (KMnO.sub.4), potassium
persulfate, nitric acid (HNO.sub.3), potassium persulfate
(K.sub.2S.sub.2O.sub.8), potassium hypochlorite (KClO),
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 peroxomonosulfate, peroxomonosulfuric acid,
ferric nitrate (Fe(NO.sub.3).sub.3), 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, 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.
32. The method of claim 31, wherein the e-waste has been pulverized
to powder, shredded, crushed to expose the metals, or a combination
thereof.
33. The method of claim 31, wherein the method is carried out at
temperature in a range from 20.degree. C. to 70.degree. C.
34. The method of claim 31, wherein (i) the first metal digestion
composition is the same as the second metal digestion composition,
or (ii) the first metal digestion composition is different than the
second metal digestion composition.
35. The method of claim 31, wherein the first metal digestion
composition further comprises at least one catalyst, wherein the at
least one catalyst comprises a glycol or a glycol ether selected
from the group consisting of ethylene glycol, propylene glycol,
butylene glycol, dipropylene glycol, 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 (DEGBE), 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. Most preferably, the catalyst comprises
diethylene glycol monobutyl ether, propylene glycol, dipropylene
glycol n-butyl ether, and combinations thereof.
36. The method of claim 31, wherein the second metal digestion
composition further comprises at least one catalyst, wherein the at
least one catalyst comprises a glycol or a glycol ether selected
from the group consisting of ethylene glycol, propylene glycol,
butylene glycol, dipropylene glycol, 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 (DEGBE), 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. Most preferably, the catalyst comprises
diethylene glycol monobutyl ether, propylene glycol, dipropylene
glycol n-butyl ether, and combinations thereof.
37. The method of claim 31, wherein the at least one complexing
agent comprises a species selected from the group consisting of
acetylacetonate, 1,1,1-trifluoro-2,4-pentanedione,
1,1,1,5,5,5-hexafluoro-2,4-pentanedione, formates, acetates,
bis(trimethylsilylamide) tetramer, 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, 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, ammonium chloride, ammonium sulfate, hydrochloric
acid, sulfuric acid, and combinations thereof.
38. The method of claim 31, wherein the at least one chelating
agent comprises hydrochloric acid or sulfuric acid.
39. The method of claim 31, wherein the at least one oxidizing
agent comprises nitric acid.
40. The method of claim 31, wherein the first and second metal
digestion compositions are devoid of cyanide-containing
compounds.
41. The method of claim 31, wherein the additive comprises a pH
adjusting agent.
42. The method of claim 41, wherein the pH adjusting agent
comprises hydroxide ions.
43. The method of claim 31, wherein the pH of the first metal
digestion composition is adjusted to pH in a range from about 6 to
about 12.
44. The method of claim 41, wherein the second metal ions are
contained in a liquid fraction and the third metal ions are
contained in a solid fraction.
45. The method of claim 31, further comprising reducing the first
metal ions to a first solid metal.
46. The method of claim 31, further comprising reducing the second
metal ions to a second solid metal.
47. The method of claim 31, further comprising reducing the third
metal ions to a third solid metal.
48. The method of claim 31, wherein the first metal is gold.
49. The method of claim 31, wherein the second metal is silver.
50. The method of claim 31, wherein the third metal is copper.
Description
FIELD
[0001] The present invention relates generally to environmentally
friendly processes for recycling printed wire boards, more
specifically environmentally friendly processes for extracting the
precious metals and base metals from IC chips and other materials
comprising said metals.
DESCRIPTION OF THE RELATED ART
[0002] Disposal of used electronic equipment, parts, and
components, including obsolete or damaged computers, computer
monitors, television receivers, cellular telephones, MP3 players,
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.
[0003] Printed wire boards (PWB's) are a common component of many
electronic systems. PWB's 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, and mercury. The PWB's include
many additional components, for example, transistors, capacitors,
heat sinks, IC's, resistors, integrated switches, processors,
etc.
[0004] PWB's are potentially a difficult waste material to process
since they generally have little usefulness once they are removed
from the electrical component 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.
PWB's 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.
[0005] Different methods have been suggested to try to combat the
waste of raw materials and environmental pollution through the ever
increasing load of scrap electronic waste. As far as PWB's are
concerned the main problem remains in the fact that different
materials are either glued, soldered or stuck together. Methods
requiring a high energy demand are needed to separate the materials
so that they can be recycled. Presently, these methods involve
shredding the PWB's into an equipped, partly equipped and
unequipped state. With regards to shredding, the first two cases
are a cause of concern when considering the environment. In the
last case the components can be removed by de-soldering, planing
down, chiselling off, grinding down, wet chemical processing (e.g.,
aqua regia, cyanide, etc.) or other similar processes. After this,
the PWB's or pieces thereof are burnt in metallurgy works. In this
process the base material, made up of glass fibre and plastic or
similar such materials, is also burnt. The melting down process of
the PWB's causes the energy requirement to be high. Refining the
melted down metals also requires further high energy and
environmentally unfriendly processes such as smelting.
[0006] The processes described herein are useful for recycling
electronic waste and for recovering valuable and/or hazardous
metals therefrom. The processes provide an alternative to smelting
for the recovery of valuable and/or hazardous metals present in
electronic waste.
SUMMARY
[0007] In one aspect, a method of removing more than one metal from
e-waste is described, said method comprising:
(a) contacting the e-waste with a first metal digestion composition
to form a first extraction liquid and a first extraction solid; (b)
separating the first extraction solid from the first extraction
liquid; (c) contacting the first extraction solid with a second
metal digestion composition to form a second extraction liquid and
a second extraction solid; (d) separating the second extraction
solid from the second extraction liquid, wherein the second
extraction liquid comprises first metal ions; and (e) contacting
the first extraction liquid with an additive to separate second
metal ions from third metal ions. Preferably, the first extraction
liquid comprises at least one chelating agent, at least one
oxidizing agent, and at least one catalyst. Preferably, the second
extraction liquid comprises at least one chelating agent, at least
one oxidizing agent, and at least one catalyst. It should be
appreciated by the skilled artisan that the first extraction liquid
can be the same as or different from the second extraction liquid.
In a preferred embodiment, the first metal comprises gold, the
second metal comprises silver and the third metal comprises
copper.
[0008] In another aspect, a method of removing more than one metal
from e-waste is described, said method comprising:
(a) contacting the e-waste with a first metal digestion composition
to form a first extraction liquid and a first extraction solid; (b)
separating the first extraction solid from the first extraction
liquid; (c) contacting the first extraction solid with a second
metal digestion composition to form a second extraction liquid and
a second extraction solid; (d) separating the second extraction
solid from the second extraction liquid, wherein the second
extraction liquid comprises first metal ions; and (e) contacting
the first extraction liquid with a pH adjusting agent to separate
second metal ions from third metal ions. Preferably, the first
extraction liquid comprises at least one chelating agent, at least
one oxidizing agent, and at least one catalyst. Preferably, the
second extraction liquid comprises at least one chelating agent, at
least one oxidizing agent, and at least one catalyst. It should be
appreciated by the skilled artisan that the first extraction liquid
can be the same as or different from the second extraction liquid.
In a preferred embodiment, the first metal comprises gold, the
second metal comprises silver and the third metal comprises
copper.
[0009] In still another aspect, a method of removing more than one
metal from e-waste is described, said method comprising:
(a) contacting the e-waste with a first metal digestion composition
to form a first extraction liquid and a first extraction solid; (b)
separating the first extraction solid from the first extraction
liquid; (c) contacting the first extraction solid with a second
metal digestion composition to form a second extraction liquid and
a second extraction solid; (d) separating the second extraction
solid from the second extraction liquid, wherein the second
extraction liquid comprises first metal ions; and (e) contacting
the first extraction liquid with an organic component that is
immiscible with the first extraction liquid to separate second
metal ions from third metal ions. Preferably, the first extraction
liquid comprises at least one chelating agent, at least one
oxidizing agent, and at least one catalyst. Preferably, the second
extraction liquid comprises at least one chelating agent, at least
one oxidizing agent, and at least one catalyst. It should be
appreciated by the skilled artisan that the first extraction liquid
can be the same as or different from the second extraction liquid.
In a preferred embodiment, the first metal comprises gold, the
second metal comprises silver and the third metal comprises
copper.
[0010] In yet another embodiment, a method of removing metals from
e-waste, said method comprising:
(a) contacting the e-waste with a composition to extract at least
two metal ions from said e-waste; (b) separating the at least two
metal ions extracted from the e-waste into individual metal ion
fractions; and (c) reducing each fraction of metal ions to solid
metals.
[0011] Other aspects, features and advantages will be more fully
apparent from the ensuing disclosure and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 illustrates the generic separation process described
herein.
[0013] FIG. 2 illustrates schematically the separation process
wherein the additive is a pH adjusting agent.
[0014] FIG. 3 illustrates schematically the separation process
wherein the additive is an organic component.
[0015] FIG. 4 illustrates the percentage of Ag. Al, Au, Cu, Fe, Mn,
Ni, Pb, Sb, Sn and Zn extracted in small scale serial extractions
using Formulation D as a function of the total mass of metal
extracted.
[0016] FIG. 5 illustrates the percentage of Ag. Al, Au, Cu, Fe, Mn,
Ni, Pb, Sb, Sn and Zn extracted in large scale serial extractions
using Formulation D as a function of the total mass of metal
extracted.
DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS THEREOF
[0017] The present invention relates generally to environmentally
friendly processes to recycle printed wire boards, more
specifically, environmentally friendly processes to recycle
components removed from the printed wire boards.
[0018] For the purposes of the present disclosure, "electronic
waste" or "e-waste" corresponds to computers, computer monitors,
television receivers, 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, integrated circuits (IC's), resistors, integrated switches,
chips, and processors).
[0019] As used herein, "metals" correspond to precious metals and
base metals that are preferably extracted from the components
removed from the printed wire boards.
[0020] As used herein, "precious metals" include the metals such as
gold, silver, platinum, palladium, alloys comprising same, and
combinations thereof.
[0021] As used herein, "base metals" corresponds to iron, nickel,
lead, zinc, alloys comprising same, and combinations thereof.
Although not base metals per se, for the purposes of the present
invention, the base metals further include copper, manganese, tin,
antimony, aluminum, as well as alloys comprising same, and
combinations thereof.
[0022] "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. %.
[0023] As used herein, "about" is intended to correspond to .+-.5%
of the stated value.
[0024] 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 hold the metal atom and/or metal ion to be
removed using the compositions described herein.
[0025] For the purposes of the present description, "printed wire
boards" and "printed circuit boards" are synonymous and may be used
interchangeably.
[0026] For the purposes of the present description, "PWB
components" include, but are not limited to, transistors,
capacitors, heat sinks, IC's, resistors, integrated switches,
chips, and processors.
[0027] As used herein, the term "releases" corresponds to the
complete removal of the component(s) from the PWB component or the
partial release of the component(s) from the PWB component, wherein
the partial release 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 release may be carried out by another
method.
[0028] As used herein, "substantially separate" corresponds to the
separation of a first metal from a material or composition
comprising at least two metals, wherein at least 75 wt % of the
first metal is separated from the material or composition,
preferably at least 85 wt %, even more preferably at least 90 wt %,
and most preferably at least 95 wt % of the first metal is
separated from the material or composition.
[0029] Compositions may be embodied in a wide variety of specific
formulations, as hereinafter more fully described. In all such
compositions, wherein specific components of the composition are
discussed in reference to weight percentage ranges including a zero
lower limit, it will be understood that such components may be
present or absent in various specific embodiments of the
composition, and that in instances where such components 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 components are employed.
[0030] In co-pending provisional patent applications 61/362,118
filed on Jul. 7, 2010 and 61/368,360 filed on Jul. 28, 2010, both
entitled "Processes for Reclaiming Precious Metals and Copper From
Printed Wire Boards," both of which are incorporated by reference
herein in their entireties, a method of removing solder from a
surface was described (e.g., a method of removing lead and/or
tin-containing solder from a printed wire board (PWB)). With the
removal of the solder, the components on the PWB are released and
said components may be separated into those that are recyclable and
those that may be further processed for disposal, reclamation of
useful materials, etc. The present disclosure relates to the
reclamation of materials from the PWB components that must be
further processed. It should be appreciated that the present
disclosure relates to the reclamation of materials from PWB
components regardless of how they are obtained (e.g., de-soldering,
planing down, chiselling off, grinding down, wet chemical
processing or using some other method known in the art).
[0031] In a first aspect, a method of removing metals from e-waste
is described and illustrated generally in FIG. 1, said method
comprising:
(a) contacting the e-waste with a composition to extract at least
two metal ions from said e-waste; (b) separating the at least two
metal ions extracted from the e-waste into individual metal ion
fractions; and (c) reducing each fraction of metal ions to
individual solid metals.
[0032] In one embodiment, a method of removing more than one metal
from e-waste is described and illustrated in FIGS. 2 and 3, said
method comprising:
(a) contacting the e-waste with a first metal digestion composition
to form a first extraction liquid and a first extraction solid; (b)
separating the first extraction solid from the first extraction
liquid; (c) contacting the first extraction solid with a second
metal digestion composition to form a second extraction liquid and
a second extraction solid; (d) separating the second extraction
solid from the second extraction liquid, wherein the second
extraction liquid comprises first metal ions; and (e) contacting
the first extraction liquid with an additive to separate second
metal ions from third metal ions.
[0033] In another embodiment, a method of removing more than one
metal from e-waste is described and illustrated in FIGS. 2 and 3,
said method comprising:
(a) contacting the e-waste with a first metal digestion composition
to form a first extraction liquid and a first extraction solid; (b)
separating the first extraction solid from the first extraction
liquid; (c) contacting the first extraction solid with a second
metal digestion composition to form a second extraction liquid and
a second extraction solid; (d) separating the second extraction
solid from the second extraction liquid, wherein the second
extraction liquid comprises first metal ions; (e) contacting the
first extraction liquid with an additive to separate second metal
ions from third metal ions; and (f) reducing the first metal ions
to a first metal, the second metal ions to a second metal, and the
third metal ions to a third metal.
[0034] The e-waste can be pulverized into a powder, shredded into
pieces, crushed, or in any other form so long as the metals
contained in the e-waste are readily exposed for extraction from
the e-waste. As defined herein, "crushed" e-waste corresponds to
any method that substantially exposes the gold and other precious
metals of the e-waste (e.g., PWB component) to the extraction
composition, e.g., cracking, pulverizing or shredding the e-waste.
Preferably, the e-waste is 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.
[0035] In one embodiment, the first metal digestion composition
comprises, consists of, or consists essentially of at least one
oxidizing agent and at least one complexing agent. In another
embodiment, the first metal digestion composition comprises,
consists of, or consists essentially of at least one oxidizing
agent, at least one complexing agent, and at least one catalyst.
The first metal digestion composition is preferably more
environmentally friendly than aqua regia or cyanide-containing
compositions. Further, the first metal digestion composition
preferably is formulated to substantially separate a first metal or
metal ion from the e-waste into a fraction that can be further
processed to reclaim said metal. For example, in one embodiment,
the first metal digestion composition can be used to separate gold
from other precious and base metals, wherein the gold is present in
the solid and the other precious and base metals are dissolved in
the first metal digestion composition. For example, the gold and
polymeric material can be present in the first extraction solid
while the first extraction liquid comprises precious metals other
than gold and other base metals.
[0036] In first extraction application, the first metal digestion
composition as described herein 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. The first extraction process using the first metal
digestion composition may be static or dynamic. Preferably, the
process is dynamic whereby agitation and/or ultrasonics occurs.
[0037] In use of the first metal digestion composition, the
composition typically is contacted with the e-waste for a time of
from about 10 minutes to about 200 minutes, preferably about 30 min
to 135 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 50.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 a first
metal or metal ion from the e-waste into a fraction that can be
further processed to reclaim said metal.
[0038] Oxidizing agents are included in the composition to oxidize
the metals to be removed into an ionic form. Oxidizing agents
contemplated herein include, but are not limited to,
methanesulfonic acid (MSA), ethanesulfonic acid, benzenesulfonic
acid, 2-hydroxyethanesulfonic acid, cyclohexylaminosulfonic acid,
n-propanesulfonic acid, n-butanesulfonic acid, or n-octanesulfonic
acid, hydrogen peroxide (H.sub.2O.sub.2), FeCl.sub.3 (both hydrated
and unhydrated), oxone (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, nitric
acid (HNO.sub.3), 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.4IO.sub.4), tetramethylammonium persulfate
((N(CH.sub.3).sub.4)S.sub.2O.sub.8)), tetrabutylammonium polyatomic
salts (e.g., tetrabutylammonium peroxomonosulfate),
peroxomonosulfuric acid, ferric nitrate (Fe(NO.sub.3).sub.3), 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, 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 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. Preferably, the
oxidizing agent comprises a peroxide compound such as hydrogen
peroxide.
[0039] 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,
ammonium sulfate, hydrochloric acid, sulfuric acid, and
combinations thereof. Preferably, the complexing agent comprises
hydrochloric acid or sulfuric acid.
[0040] The catalyst is added to enhance the removal rate of the
metal(s) from the e-waste. Preferably, the catalyst comprises a
glycol or a glycol ether selected from the group consisting of
ethylene glycol, propylene glycol, butylene glycol, dipropylene
glycol, 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 (DEGBE),
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.
Most preferably, the catalyst comprises diethylene glycol monobutyl
ether, propylene glycol, dipropylene glycol n-butyl ether, and
combinations thereof. Most preferably, the catalyst comprises
DEGBE. When included, the amount of catalyst is in a range from
about 0.01 wt % to about 10 wt %, preferably about 0.1 wt % to
about 5 wt %, and most preferably about 0.5 wt % to about 1 wt %.
Although not wishing to be bound by theory, it is thought that by
changing the chain length of the catalyst (e.g., methyl versus
butyl), that the selectivity of the first extraction composition
for certain metals can be varied.
[0041] Preferably, in one embodiment, the first metal digestion
composition comprises, consists of, or consists essentially of
hydrochloric acid and hydrogen peroxide. In another embodiment, the
first metal digestion composition comprises, consists of, or
consists essentially of hydrochloric acid, hydrogen peroxide, and a
glycol or glycol ether. In yet another embodiment, the first metal
digestion composition comprises, consists of, or consists
essentially of hydrochloric acid, hydrogen peroxide, and diethylene
glycol monobutyl ether. The first metal digestion composition is
substantially devoid of nitric acid and cyanide-containing
components. Preferably, the first metal digestion compositions are
water soluble, non-corrosive, non-flammable and of low
toxicity.
[0042] As illustrated in FIGS. 2 and 3, following the first
extraction with the first metal digestion composition, there can be
a first extraction solid and a first extraction liquid. As
introduced hereinabove, the first metal digestion composition
preferably is formulated to substantially separate a first metal or
metal ion from the e-waste into a fraction that can be further
processed to reclaim said first metal. For example, in one
embodiment, the first metal digestion composition can be used to
separate gold from other precious and base metals. As illustrated
in FIGS. 2 and 3, the first extraction solid can comprise gold,
while the first extraction liquid can comprise ions of other
precious and base metals (e.g., silver and copper).
[0043] Following the first extraction, the first extraction solid
can be separated from the first extraction liquid using methods
well known in the art (e.g., filtration means, centrifugation and
decanting, etc.).
[0044] As illustrated in FIGS. 2 and 3, once the first extraction
solid is obtained, a second extraction can commence, wherein a
second metal digestion composition is combined with the first
extraction solid which comprises a first metal (e.g., gold). The
second metal digestion composition can be the same as or different
from the first metal digestion composition. Preferably, the second
metal digestion composition is the same as the first metal
digestion composition, wherein the time and/or temperature of
contacting of the first metal digestion composition with the
e-waste is different than the time and/or temperature of contacting
of the second metal digestion composition with the first extraction
solid, as will be clarified in the examples herein.
[0045] In second extraction application, the second metal digestion
composition as described herein is contacted in any suitable manner
to the first extraction solid, e.g., by spraying the composition on
the first extraction solid, by dipping (in a volume of the
composition) of the first extraction solid, by contacting the first
extraction solid 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 first
extraction solid. The second extraction process using the second
metal digestion composition may be static or dynamic. Preferably,
the process is dynamic whereby agitation and/or ultrasonics
occurs.
[0046] In use of the second metal digestion composition, the
composition typically is contacted with the first extraction solid
for a time of from about 10 minutes to about 200 minutes,
preferably about 30 min to 135 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 50.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 a first metal ion from the first extraction
solid into a fraction that can be further processed to reclaim said
metal.
[0047] In one embodiment, the second metal digestion composition
comprises, consists of, or consists essentially of at least one
oxidizing agent and at least one complexing agent. In another
embodiment, the second metal digestion composition comprises,
consists of, or consists essentially of at least one oxidizing
agent, at least one complexing agent, and at least one catalyst.
The second metal digestion composition is preferably more
environmentally friendly than, and is substantially devoid of,
nitric acid and cyanide-containing compositions. Further, the
second metal digestion composition preferably is formulated to
substantially separate the first metal ion from the first
extraction solid into a fraction (e.g., an aqueous fraction) that
can be further processed to reclaim said metal. For example, in one
embodiment, the second metal digestion composition can be used to
separate gold ions from the first extraction solid, wherein the
second extraction solid comprises polymeric material. The oxidizing
agents, complexing agents and catalysts are the same as described
hereinabove.
[0048] As illustrated in FIGS. 2 and 3, following the second
extraction with the second metal digestion composition, there can
be a second extraction solid and a second extraction liquid. As
introduced hereinabove, the second metal digestion composition
preferably is formulated to substantially separate the first metal
ion (e.g., gold) from the first extraction solid into a fraction
(e.g., the second extraction liquid) that can be further processed
to reclaim said metal. For example, in one embodiment, the second
metal digestion composition can be used to separate gold ions from
the first extraction solid. As illustrated in FIGS. 2 and 3, the
second extraction liquid can comprise gold ions, while the second
extraction solid can comprise residual plastics. It should be
appreciated by the skilled artisan that the residual plastics may
be disposed of or alternatively, recycled or reclaimed for reuse.
Following the extraction of the metal ions into the second
extraction liquid, the metal can be obtained by reducing the metal
ions, as will be discussed at length hereinbelow.
[0049] Following separation of the first extraction solid from the
first extraction liquid, an additive can be added to further
separate metals that are present in the first extraction liquid.
The additive can be a pH adjusting agent or an organic phase such
that upon addition of the additive to the first extraction liquid,
a second metal ion is separated from a third metal ion based using
precipitation or separation. Alternatively, or in addition to the
addition of the pH adjusting agent or organic additive, the
temperature of the contacting conditions can be varied.
[0050] It is known in the art that some metal ions readily form
hydroxide solids as the pH of a solution is raised. Accordingly, in
one embodiment, the additive is a pH adjusting agent wherein the pH
of the first extraction liquid is raised to a pH in a range from
about 6 to about 12, preferably about 9 to about 11, to separate a
second metal ion from the first extraction liquid. pH adjusting
agents contemplated herein preferably include hydroxide ions such
as alkali and alkaline earth metal hydroxides such as sodium
hydroxide, potassium hydroxide, rubidium hydroxide, cesium
hydroxide, magnesium hydroxide, calcium hydroxide, strontium
hydroxide, or barium hydroxide. Alternatively, the pH adjusting
agents can include quaternary ammonium bases having the formula
[NR.sup.1R.sup.2R.sup.3R.sup.4].sup.+OH.sup.-, wherein R.sup.1,
R.sup.2, R.sup.3 and R.sup.4 can be the same as or different from
one another and are selected from the group consisting of hydrogen,
straight-chained or branched C.sub.1-C.sub.6 alkyls (e.g., methyl,
ethyl, propyl, butyl, pentyl, hexyl), C.sub.6-C.sub.10 aryls (e.g.,
benzyl), and combinations thereof. The addition of the pH adjusting
agent to the first extraction liquid preferably substantially
separates a second metal ion from the first extraction liquid into
a fraction that can be further processed to reclaim said metal. For
example, as illustrated in FIG. 2, following the pH ramp to a range
of about 6 to about 12, preferably about 9 to about 11, a
precipitate (the "pH ramp solid") comprising metal hydroxides will
form, said precipitate being readily separable from the remaining
liquid comprising the second metal ion (the "pH ramp liquid"). The
pH ramp solid can be separated from the pH ramp liquid using
methods well known in the art (e.g., filtration means,
centrifugation and decanting, etc.). For example, the second metal
ions in the pH ramp liquid can comprise silver ions, which are
substantially separable from other metals in the first extraction
liquid which readily formed hydroxide solids in the presence of a
pH adjusting agent. The pH ramp liquid comprising silver ions can
be reduced to silver metal in a subsequent step to be discussed
below.
[0051] The pH ramp solid remaining subsequent to separation from
the pH ramp liquid can comprise several metals, most notably
copper, in the form of metal hydroxide salts. The copper ions can
subsequently be extracted from the pH ramp solid into an aqueous
phase, followed by reduction to copper metal. For example, the
copper ions can be extracted from the solid using a dilute sulfuric
acid solution.
[0052] Accordingly, another embodiment relates to a method of
removing more than one metal from e-waste as illustrated in FIG. 2,
said method comprising:
(a) contacting the e-waste with a first metal digestion composition
to form a first extraction liquid and a first extraction solid; (b)
separating the first extraction solid from the first extraction
liquid; (c) contacting the first extraction solid with a second
metal digestion composition to form a second extraction liquid and
a second extraction solid; (d) separating the second extraction
solid from the second extraction liquid, wherein the second
extraction liquid comprises first metal ions; and (e) contacting
the first extraction liquid with a pH adjusting agent to separate
second metal ions from third metal ions.
[0053] Still another embodiment relates to a method of removing
more than one metal from e-waste as illustrated in FIG. 2, said
method comprising:
(a) contacting the e-waste with a first metal digestion composition
to form a first extraction liquid and a first extraction solid; (b)
separating the first extraction solid from the first extraction
liquid; (c) contacting the first extraction solid with a second
metal digestion composition to form a second extraction liquid and
a second extraction solid; (d) separating the second extraction
solid from the second extraction liquid, wherein the second
extraction liquid comprises first metal ions; (e) contacting the
first extraction liquid with a pH adjusting agent to separate
second metal ions from third metal ions; and (f) reducing the first
metal ions to a first metal, the second metal ions to a second
metal, and the third metal ions to a third metal.
[0054] In another embodiment, the additive is an organic component
which is added to the first extraction liquid to separate a metal
ion (e.g., the second metal ions) from another metal ion (e.g., the
third metal ions). Specifically, the organic component is added to
the first extraction liquid and two phases will form (the organic
component is substantially immiscible with the first extraction
liquid, which is aqueous), one phase comprising the second metal
ions and the other phase comprising the third metal ions. Organic
components contemplated herein include hydroxyoximes such as
ACORGA.RTM. M5774 metal extraction reagent (Cytec Industries, Inc.)
or the equivalent thereof. The addition of the organic component to
the first extraction liquid preferably substantially separates a
second metal ion from the first extraction liquid into a fraction
that can be further processed to reclaim said metal. For example,
referring to FIG. 3, the aqueous phase can comprise the silver ions
and the organic phase can comprise copper ions. The pH of the
aqueous phase comprising the silver ions can be ramped to a range
from about 6 to about 12, preferably about 9 to about 11, as
described hereinabove, wherein the silver ions are substantially
separable from other metals in the aqueous phase which readily
formed hydroxide solids in the presence of a pH adjusting agent.
Following separation of the pH ramp solid from the pH ramp liquid,
the silver ions in the pH ramp liquid can be reduced to obtain
silver metal. The third metal ions can be extracted out of the
organic phase into an aqueous phase and the aqueous phase
comprising the third metal ions can be reduced to obtain the copper
metal. The extraction of the copper ions from the organic phase can
be effectuated using dilute sulfuric acid.
[0055] 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, glucose and sodium citrate.
[0056] Accordingly, another embodiment relates to a method of
removing more than one metal from e-waste as illustrated in FIG. 3,
said method comprising:
(a) contacting the e-waste with a first metal digestion composition
to form a first extraction liquid and a first extraction solid; (b)
separating the first extraction solid from the first extraction
liquid; (c) contacting the first extraction solid with a second
metal digestion composition to form a second extraction liquid and
a second extraction solid; (d) separating the second extraction
solid from the second extraction liquid, wherein the second
extraction liquid comprises first metal ions; and (e) contacting
the first extraction liquid with an organic component that is
immiscible with the first extraction liquid to separate second
metal ions from third metal ions.
[0057] Yet another embodiment relates to a method of removing more
than one metal from e-waste as illustrated in FIG. 3, said method
comprising:
(a) contacting the e-waste with a first metal digestion composition
to form a first extraction liquid and a first extraction solid; (b)
separating the first extraction solid from the first extraction
liquid; (c) contacting the first extraction solid with a second
metal digestion composition to form a second extraction liquid and
a second extraction solid; (d) separating the second extraction
solid from the second extraction liquid, wherein the second
extraction liquid comprises first metal ions; (e) contacting the
first extraction liquid with an organic component that is
immiscible with the first extraction liquid to separate second
metal ions from third metal ions; and (f) reducing the first metal
ions to a first metal, the second metal ions to a second metal, and
the third metal ions to a third metal.
[0058] The compositions described herein are easily formulated by
simple addition of the respective ingredients and mixing to
homogeneous condition. Furthermore, the 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.
[0059] Using the methods described herein, greater than 90 wt % of
the metals in the e-waste can be reclaimed.
[0060] In another aspect, the methods described herein can be used
in the mining industry to separate metals from ores. For example,
instead of starting with e-waste, the original material to be
extracted using the first metal digestion composition is an ore or
some other product of the mining industry.
[0061] In another aspect, a method of removing a metal from e-waste
is described, said method comprising contacting the e-waste with a
composition under conditions to extract a metal ion from said
e-waste into an extraction composition, wherein said composition
comprises, consists of, or consists essentially of at least one
oxidizing agent, at least one complexing agent, and at least one
catalyst. Suitable oxidizing agent(s), complexing agent(s) and
catalyst(s) have been described herein. In one embodiment, the
composition comprises, consists of, or consists essentially of
hydrochloric acid, hydrogen peroxide, and a glycol or glycol ether.
In another embodiment, the composition comprises, consists of, or
consists essentially of hydrochloric acid, hydrogen peroxide, and
diethylene glycol monobutyl ether. In a preferred embodiment, the
method further comprises separating the extraction composition
comprising the metal ion from the solid e-waste. Solid metal can be
obtained by reducing the metal ion in the extraction composition
(e.g., with a reducing agent suitable for such purpose). In an
embodiment, the e-waste treated with the extraction compositions
described herein may contain two or more different metals.
[0062] In still another aspect, a method of removing a metal from
e-waste is described, said method comprising: (a) contacting the
e-waste with a composition under conditions to extract a metal ion
from said e-waste into an extraction composition; (b) separating
the extraction composition comprising the metal ion from the solid
e-waste; and (c) obtaining solid metal from the extraction
composition comprising the metal ion, wherein said composition
comprises, consists of, or consists essentially of at least one
oxidizing agent, at least one complexing agent, and at least one
catalyst. Suitable oxidizing agent(s), complexing agent(s) and
catalyst(s) have been described herein. In one embodiment, the
composition comprises, consists of, or consists essentially of
hydrochloric acid, hydrogen peroxide, and a glycol or glycol ether.
In another embodiment, the composition comprises, consists of, or
consists essentially of hydrochloric acid, hydrogen peroxide, and
diethylene glycol monobutyl ether. Solid metal can be obtained by
reducing the metal ion in the extraction composition (e.g., with a
reducing agent suitable for such purpose). In an embodiment, the
e-waste treated with the extraction compositions described herein
may contain two or more different metals.
[0063] In another aspect, a method of separating a first metal from
at least a second metal, said method comprising contacting a
material comprising the first and second metal with a composition
under conditions to extract a first metal ion from said material
into an extraction composition, wherein said composition comprises,
consists of, or consists essentially of at least one oxidizing
agent, at least one complexing agent, and at least one catalyst.
Suitable oxidizing agent(s), complexing agent(s) and catalyst(s)
have been described herein. In one embodiment, the composition
comprises, consists of, or consists essentially of hydrochloric
acid, hydrogen peroxide, and a glycol or glycol ether. In another
embodiment, the composition comprises, consists of, or consists
essentially of hydrochloric acid, hydrogen peroxide, and diethylene
glycol monobutyl ether. In another aspect, the method further
comprises separating the extraction composition comprising the
first metal ion from the material. Solid first metal can be
obtained by reducing the first metal ion in the extraction
composition (e.g., with a reducing agent suitable for such
purpose).
[0064] In another aspect, a method of separating a first metal from
at least a second metal, said method comprising: (a) contacting a
material comprising the first and second metal with a composition
under conditions to extract a first metal ion from said material
into an extraction composition; (b) separating the extraction
composition comprising the first metal ion from the material; and
(c) obtaining a solid first metal from the first metal ion, wherein
said composition comprises, consists of, or consists essentially of
at least one oxidizing agent, at least one complexing agent, and at
least one catalyst. Suitable oxidizing agent(s), complexing
agent(s) and catalyst(s) have been described herein. In one
embodiment, the composition comprises, consists of, or consists
essentially of hydrochloric acid, hydrogen peroxide, and a glycol
or glycol ether. In another embodiment, the composition comprises,
consists of, or consists essentially of hydrochloric acid, hydrogen
peroxide, and diethylene glycol monobutyl ether. Solid first metal
can be obtained by reducing the first metal ion in the extraction
composition (e.g., with a reducing agent suitable for such
purpose).
[0065] The features and advantages of the invention are more fully
shown by the illustrative examples discussed below.
Example 1
[0066] The first extraction of e-waste using variations of the
first metal digestion composition described herein was performed.
The e-waste was ground into a course powder. Single and multiple
digestions of the powder were performed in duplicate and the first
extraction compositions and the first extraction solids were
analyzed using Inductively Coupled Plasma Mass Spectrometry
(ICP-MS). All digestions were performed using 500 mg-10 g powder in
10 mL-200 mL of first metal digestion composition. Agitation
occurred throughout the digestions. Digestion times ranged from
about 30 minutes to about 135 minutes at temperatures in a range
from about room temperature to about 50.degree. C.
[0067] The first metal digestion compositions tested were as
follows:
[0068] Formulation A: Aqua regia (Control, 3:1 HCl:HNO3)
[0069] Formulation B: 37% HCl:30% H2O2 (90%: 10% by vol.)
[0070] Formulation C: 37% HCl:30% H2O2 (90%:10% by vol.) with
NH.sub.4Cl or NH.sub.4SCN
[0071] Formulation D: 37% HCl:30% H2O2 (90%:10% by vol.+0.75 vol. %
DEGBE)
[0072] Formulation E: 37% HCl:30% H2O2 (90%:10% by vol.+0.75 vol. %
propylene glycol)
[0073] Formulation F: 37% HCl:30% H2O2 (90%:10% by vol.+0.75 vol. %
DPGBE)
[0074] Formulation G: Etidronic acid+DEGBE (99%:1% by vol.)
[0075] Formulation H: 1:1:6
H.sub.2SO.sub.4:H.sub.2O.sub.2:H.sub.2O
[0076] Formulation I: 37% HCl:30% H2O2 (90%: 10% by vol.+0.5 vol. %
DEGBE)
[0077] Formulation J: 37% HCl:30% H2O2 (90%:10% by vol.+1 vol. %
DEGBE)
[0078] Formulation K: 95% H.sub.2SO.sub.4:30% H.sub.2O.sub.2
(90%:10% by vol.)
[0079] Formulation L: 95% H.sub.2SO.sub.4:30% H.sub.2O.sub.2
(90%:10% by vol.+0.75 vol. % DEGBE
[0080] Formulation M: 37% HCl:30% H2O2 (90%:10% by vol.+25 vol. %
DEGBE)
[0081] Formulation N: 75 vol. % Etidronic acid+25 vol. % DEGBE
[0082] Formulation O: Etidronic acid+DEGBE+NH.sub.4Cl (94%:1%:5% by
vol.)
[0083] Experimental results for the extraction of gold, silver and
copper from e-waste using the methods described herein and the
formulations are shown in Table 1 below. The aqua regia
(formulation A) result was normalized to allow for easy comparison
to other digests.
TABLE-US-00001 TABLE 1 Metal extraction efficiencies relative to
aqua regia (formulation A). Formu- Au/ Ag/ Cu/ lation Conditions
ppm ppm ppm A 100.degree. C., 60 min 100% 100% 100% B room
temperature (RT), 30 min, 101% 36% 32% small scale* B 50.degree.
C., 30 min, small scale 54% 54% 66% I RT, 30 min, small scale 126%
71% 44% I 50.degree. C., 30 min, small scale 42% 40% 57% J RT, 30
min, small scale 132% 90% 72% J 50.degree. C., 30 min, small scale
0% 79% 95% H 50.degree. C., 30 min, small scale 0% 8% 58% K
50.degree. C., 30 min, small scale 0% 2% 1% D RT, 30 min, small
scale 55% 40% 33% D 50.degree. C., 30 min, small scale 14-16%
81-83% 46-100% D RT, 135 min, small scale, 198% 111% 50% serial
extraction (total) D 50.degree. C., 135 min, large
scale,.sup..dagger. 24-42% 57-83% 63-77% serial extraction (total)
E RT, 30 min, small scale 164% 101% 71% E 50.degree. C., 30 min,
small scale 38% 26% 24% F RT, 30 min, small scale 106% 31% 23% F
50.degree. C., 30 min, small scale 0% 62% 71% *small scale is 500
mg e-waste + 10 mL digestion formulation .sup..dagger.large scale
is 10 g e-waste + 200 mL digestion formulation
[0084] It can be seen that a variety of digestion methods yielded
greater than 90% extraction efficiency of one or more metals
relative to aqua regia (formulation A). Values greater than 100%
indicated an extraction efficiency greater than aqua regia for that
metal. Multiple extractions can result in 100% recovery of Au, Ag
and Cu relative to aqua regia.
[0085] It can be seen that formulations and reaction conditions can
be selected to ensure the selective extraction of silver and copper
ions relative to gold. For example, the first extraction can be
carried out using formulation J as the first metal digestion
composition at 50.degree. C. for 30 minutes and silver ions and
copper ions are extracted with 79% and 95% efficiency, respectively
(relative to aqua regia), while no gold is extracted. Clean
formulation J can then be used as the second metal digestion
composition at room temperature for 30 minutes and gold ions can be
readily extracted from the e-waste. In another alternative, the
first metal digestion composition can be formulation F at
50.degree. C. for 30 minutes while the second metal digestion
composition can be clean formulation F at room temperature for 30
minutes. It should be appreciated that these are just examples to
demonstrate that it is possible to formulate a digestion
composition and select the appropriate temperature and time to
selectively extract metal ions relative to gold for the first
extraction step described herein.
[0086] An alternative way to determine the efficiency of metal
extraction is to determine the total mass of a single metal
extracted into the liquid relative to the total mass of that metal
in the e-waste powder. In this method, the e-waste powder is
digested and then the liquid is separated from the solid, the
liquid and solid are both analyzed to determine their metal
contact, and the percent metal in the liquid relative to the total
amount of metal in the e-waste calculated. If the extraction is
highly efficient, the metals of interest should be found in the
liquid, having been extracted from the solid. Results are shown in
Table 2.
TABLE-US-00002 TABLE 1 Metal extraction efficiencies relative to
the total mass of the metal extracted. Formu- Au/ Ag/ Cu/ lation
Conditions ppm ppm ppm M 50.degree. C., 30 min, small scale* 47%
47% 9% I room temperature (RT), 30 min, 61% 74% 87% small scale I
50.degree. C., 30 min, small scale 23% 84% 99% J RT, 30 min, small
scale 66% 98% 100% J 50.degree. C., 30 min, small scale 0% 99% 100%
E RT, 30 min, small scale 86% 99% 100% E 50.degree. C., 30 min,
small scale 23% 81% 60% F RT, 30 min, small scale 76% 63% 47% D
50.degree. C., 30 min, large scale, .sup..dagger. 0% 69-88% 98%
serial, 1.sup.st extraction D 50.degree. C., 105 min, large scale,
72-100% 100% 100% serial, total H 50.degree. C., 30 min, small
scale 0% 1% 48% L 50.degree. C., 30 min, small scale 6% 71% 100% L
50.degree. C., 30 min, small scale 26% 99% 29% G 50.degree. C., 30
min, small scale 28% 2% 87% N 50.degree. C., 30 min, small scale
28% 26% 96% N 50.degree. C., 30 min, small scale 19% 6% 62% O
50.degree. C., 30 min, small scale 0% 88% 91% *small scale is 500
mg e-waste + 10 mL digestion formulation .sup..dagger. large scale
is 10 g e-waste + 200 mL digestion formulation
[0087] It can be seen that the most efficient extraction was the
formulation D serial extraction, wherein the e-waste was digested
in formulation D at 50.degree. C. for 30 minutes, the digestion
solution was removed, the remaining e-waste was digested in clean
formulation D for another 75 min at 50.degree. C., and the
digestion solution removed.
Example 2
[0088] Small scale serial extractions were performed using
formulation D by extracting the e-waste at 50.degree. C. for 30
minutes, followed by two additional extractions with clean
formulation D for 30 min and 75 min. The results are shown in FIG.
4, wherein at 50.degree. C. all metals except Au were strongly
extracted in the first 30 minute extraction and 93% of the total
mass of Au was extracted in the second 30 minute and third 75
minute extraction.
[0089] Large scale serial extractions (scaled 20 times relative to
the small scale serial extraction) were performed using formulation
D by extracting the e-waste at 50.degree. C. for 30 minutes,
followed by an additional extraction with clean formulation D for
105 min. The results are shown in FIG. 5, wherein better separation
of the Ag and Cu from the Au was achieved at the larger scale.
[0090] Accordingly, serial extractions could be used to separated
Ag and Cu from Au.
[0091] Then, starting with an aliquot of the small scale first
extraction liquid of this example (formulation D, 50.degree. C., 30
minutes), which is substantially devoid of Au, NaOH was added
dropwise (see, e.g., FIG. 2, pH ramp). A precipitate formed at
about pH 6. Both the precipitate (pH ramp solid at pH 6) and
remaining liquid (pH ramp liquid at pH 10) were analyzed for metal
ion content using ICP-MS. The results are shown in Table 3:
TABLE-US-00003 TABLE 3 Parts per million of metal ions in pH ramp
solid relative to pH ramp liquid for small scale extraction. Au Ag
Cu Al Fe Mn Ni Pb Sb Sn Zn pH ramp liquid 0 88 0 0 0 64 42 0 2 0 6
pH ramp solid 0 12 100 100 100 36 58 100 98 100 93
[0092] It can be seen that with the small scale extraction pH ramp
that the pH ramp liquid contained mostly Ag (82%) while the
precipitate contained 100% of the copper and most of the remaining
metals.
[0093] Then, starting with an aliquot of the large scale first
extraction liquid of this example (formulation D, 50.degree. C., 30
minutes), which is substantially devoid of Au, NaOH was added
dropwise. A precipitate formed at about pH 6. Both the precipitate
(pH ramp solid at pH 6) and remaining liquid (pH ramp liquid at pH
12) were analyzed for metal ion content using ICP-MS. The results
are shown in Table 4:
TABLE-US-00004 TABLE 3 Parts per million of metal ions in pH ramp
solid relative to pH ramp liquid for large scale extraction. Au Ag
Cu Al Fe Mn Ni Pb Sb Sn Zn pH ramp liquid 0 100 1 100 0 0 0 0 0 84
0 pH ramp solid 0 0 99 0 100 100 100 0 100 16 100
[0094] It can be seen that with the large scale extraction pH ramp
that the pH ramp liquid contained 100% Ag while the precipitate
contained 99% of the copper and most of the remaining metals.
[0095] Alternatively, an organic component can be combined with the
first extraction liquid to enable selective precipitation of
desired metal ions (see, e.g., FIG. 3, add additive). An organic
component of interest is M-5774, which is a proprietary mixture of
oximes and aldoximes which is selective for Cu ions and phase
separates from aqueous solutions. The organic layer extracts Cu
ions from aqueous solutions comprising same. Following extraction
into M-5774, copper ions can be recovered from the organic M-5774
layer using a dilute sulfuric acid wash.
[0096] Starting with an aliquot of the small scale first extraction
liquid of this example (formulation D, 50.degree. C., 30 minutes),
which is substantially devoid of Au, M-5774 was added under
different pH and temperature conditions for 30 minutes (see, e.g.,
FIG. 3, add additive). Two layers were created, one aqueous and one
organic. Following separation of the layers, the aqueous layer was
analyzed for metal ion content using ICP-MS. The results are shown
in Table 5:
TABLE-US-00005 TABLE 5 Parts per million of metal ions in aqueous
phase for small scale extraction. Au Ag Cu Al Fe Mn Ni Pb Sb Sn Zn
pH < 1, 50.degree. C. 24.19 94.10 100.57 143.02 9.11 122.72
125.97 131.84 87.90 93.08 150.27 pH 4, 50.degree. C. 0 112.18 14.95
184.25 93.80 94.82 97.00 24.85 92.50 86.32 49.13 pH < 1, RT
13.98 101.61 103.07 113.49 5.12 97.89 99.67 111.94 57.15 67.72
100.06 pH 4, RT 0 98.26 8.45 171.97 80.81 84.41 86.97 19.03 76.09
69.50 42.73
[0097] It can be seen that with the small scale extraction, at pH 4
and room temperature, Ag (98%) can be selectively extracted from Cu
(8%).
Example 3
[0098] Once separated, for example as described in the description
herein, the metal ions are preferably reduced to metal solid.
Preferably, the reducing agent is a so-called environmentally
friendly chemical. Moreover, preferably the reduction occurs
rapidly with minimal heating requirements.
[0099] In order to gauge effectiveness of the reducing agents, the
reduction of standard solutions of Au.sup.+3 (ICP gold standard in
dilute HCl (approximately 0.05 M)), Ag.sup.+ (1 M AgNO.sub.3) and
Cu.sup.+2 (1 M CuSO.sub.4) was performed. Environmentally friendly
reducing agents were added to the standard solutions and time,
temperature and pH were controlled. The pH was adjusted by adding
HCl, NaHCO.sub.3 or NaOH before or after addition of the
environmentally friendly reducing agent. The pH of the solutions
influences the oxidation state of the metal ion and therefore the
potential for reduction to the metal solid. The initial amount of
metal ion in the solution and the final amount of solid collected
following the reduction were compared to determine percent
recovery.
[0100] Six environmentally friendly chemical reducing agents were
tested: ascorbic acid, diethyl malonate, sodium metabisulfite,
polyphenon 60 (P60, green tea extract), D-glucose and sodium
citrate, as will be discussed individually below.
Ascorbic Acid
[0101] Ascorbic acid (AA) was added to each of the Au.sup.3+,
Ag.sup.+ and Cu.sup.2+ solutions at the conditions disclosed in
Table 6 and room temperature for less than 1 hour and the solids
recovered were analyzed using ICP-MS to test for purity. The
results are shown in Table 6.
TABLE-US-00006 TABLE 6 Ascorbic acid reduction results Elemental
Metal Ion Conditions Recovered? Analysis Notes Au.sup.+3 Au.sup.3+
in soln at pH 1, Brown solid formed, 98% Au High purity AA soln at
pH 1 104% formation of Au(s) Au.sup.+3 Au.sup.3+ in soln at pH 1,
Brown solid formed, 87% Au Au(s) formation, AA soln at pH 5.5 103%
likely contains trace salts Au.sup.+3 Au.sup.3+ in soln at pH 7,
Brown solid formed, 73% Au Likely contains AA soln at pH 5.5 + 107%
oxide and chloride base (NaOH) salts Au.sup.+3 Au.sup.3+ in soln at
pH 10, Brown solid formed, 39% Au Likely contains AA soln at pH 5.5
+ 113% oxide and chloride base (NaOH) salts Ag.sup.+ Ag.sup.+ in
soln at pH 7, Gray solid formed, 70% Ag Likely contains AA soln at
pH 1 103% oxide and chloride salts Ag.sup.+ Ag.sup.+ in soln at pH
7, Dark gray solid 56% Ag Likely contains AA soln at pH 5.5 formed,
111% oxide salts Cu.sup.2+ Cu.sup.2+ in soln at pH 1, Red-orange
solid, 78% Cu Likely contains AA soln at pH 5.5 98% chloride salts
Cu.sup.2+ Cu.sup.2+ in soln at pH 7, Copper colored 98% Cu High
purity AA soln at pH 5.5 solid, 110% formation of Cu(s)
[0102] It can be seen that high purity Au and Cu was recovered
using ascorbic acid in less than one hour.
Diethyl Malonate
[0103] Diethyl malonate is not miscible with aqueous solutions and
Au can be selectively extracted into the organic layer, forming the
CH.sub.2(COOC.sub.2H.sub.5)Au(H.sub.2O).sub.4Cl.sub.3 complex at
low pH. Thereafter, the organic extract containing the Au can be
washed by mixing with HNO.sub.3 to remove impurities and then
FeSO.sub.4 at 80.degree. C. can be used to reduce to Au metal.
[0104] Diethyl malonate (DEM) was added to each of the Au.sup.3+,
Ag.sup.+ and Cu.sup.2+ solutions at the conditions disclosed in
Table 7 and room temperature for less than 1 hour and the solids
recovered were analyzed using ICP-MS to test for purity. The
results are shown in Table 7.
TABLE-US-00007 TABLE 7 Diethyl malonate reduction results Elemental
Metal Ion Conditions Recovered? Analysis Notes Au.sup.+3 Au.sup.3+
in soln at pH 1 No solid formed N/A Au move to DEM layer Au.sup.+3
Au.sup.3+ in soln at pH 7 Brown solid formed 87% Au Au(s) formed,
may contain oxide or chloride salts Au.sup.+3 Au.sup.3+ in soln at
pH 10, Light yellow solid 93% Au Au(s) formed, may 50.degree. C.
for 20 min formed, 94% contain oxide or chloride salts Au.sup.+3
Au.sup.3+ in soln at pH 10, Yellow solid formed, 56% Au Likely
contains 50.degree. C. for 150 min 55% oxide or chloride salts
Ag.sup.+ Ag.sup.+ in soln at pH 4 No solid formed N/A Two clear
layers Cu.sup.2+ Cu.sup.2+ in soln at pH 1 No solid formed N/A
Addition of DEM formed two layers Cu.sup.2+ Cu.sup.2+ in soln at pH
7 No solid formed N/A Addition of DEM formed two layers Cu.sup.2+
Cu.sup.2+ in soln at pH 10 No solid formed N/A Precipitate formed
upon NaOH addition, Cu(OH).sub.2
[0105] It can be seen that diethyl malonate was more effective for
Au reduction, relative to either Ag or Cu.
Sodium Metabisulfite
[0106] Sodium metabisulfite (SMB) was added to each of the
Au.sup.3+, Ag.sup.+ and Cu.sup.2+ solutions at the conditions
disclosed in Table 8 and room temperature for less than 1 hour and
the solids recovered were analyzed using ICP-MS to test for purity.
The results are shown in Table 8.
TABLE-US-00008 TABLE 8 Sodium metabisulfite reduction results
Elemental Metal Ion Conditions Recovered? Analysis Notes Au.sup.+3
Au.sup.3+ in soln at pH 1 Yellow solid formed 95% Au High purity
formation of Au(s) Au.sup.+3 Au.sup.3+ in soln at pH 7 Au mirror
observed 97% Au High purity at >3 hr, 142% formation of Au(s)
Au.sup.+3 Au.sup.3+ in soln at pH 10 Au mirror formed 36% Au 36%
Au(s) + 64% at >3 hr, 140% SMB contamination Ag.sup.+ Ag.sup.+
in soln at pH 1 White solid (AgCl) N/A AgCl forms when formed, 90%
adjusted to pH 1 with HCl Ag.sup.+ Ag.sup.+ in soln at pH 4 White
solid formed, 61% Ag 61% Ag(s) + 39% 92% SMB contamination Ag.sup.+
Ag.sup.+ in soln at pH 7 White solid formed, 48% Ag 48% Ag(s) + 52%
106% SMB contamination Ag.sup.+ Ag.sup.+ in soln at pH 10 Brown
solid formed, 50% Ag 50% Ag(s) + 50% solid turned white SMB
contamination with SMB addition, 106% Cu.sup.2+ Cu.sup.2+ in soln
at pH 1 White solid formed, 33% Ag 33% Cu(s) + 67% 24% SMB
contamination Cu.sup.2+ Cu.sup.2+ in soln at pH 7 White solid
formed, 53% Ag Likely contains Cu 30% oxide salt Cu.sup.2+
Cu.sup.2+ in soln at pH 10 Blue solid formed, 28% Ag 28% Cu(s) +
72% solid turned brown SMB contamination with SMB addition, 70%
[0107] It can be seen that sodium metabisulfite was more effective
for Au reduction, relative to either Ag or Cu.
Polyphenon 60
[0108] Polyphenon 60 (P60) was added to each of the Au.sup.3+,
Ag.sup.+ and Cu.sup.2+ solutions at the conditions disclosed in
Table 9 and room temperature and the solids recovered were analyzed
using ICP-MS to test for purity. The results are shown in Table
9.
TABLE-US-00009 TABLE 9 P60 reduction results Elemental Metal Ion
Conditions Recovered? Analysis Notes Au.sup.+3 Au.sup.3+ in soln at
pH 1 Red solid started to 32% form after 15 min Ag.sup.+ Ag.sup.+
in soln at pH 4 Silver mirror formed 100% Ag(s) formed at after 15
min, 25% high purity. Ag at >4 hr continues to fall out of
solution over time. Cu.sup.2+ Cu.sup.2+ in soln at pH 7 No solid
formed N/A
[0109] It can be seen that P60 was more effective for Ag reduction,
relative to either Au or Cu.
Glucose
[0110] Glucose was added to each of the Au.sup.3+, Ag.sup.+ and
Cu.sup.2+ solutions at the conditions disclosed in Table 10 and the
solids recovered were analyzed using ICP-MS to test for purity. The
results are shown in Table 10.
TABLE-US-00010 TABLE 10 Glucose reduction results Elemental Metal
Ion Conditions Recovered? Analysis Notes Au.sup.+3 Au.sup.3+ in
soln at pH 1 No solid formed N/A (RT) Au.sup.+3 Au.sup.3+ in soln
at pH 1 No solid formed N/A (100.degree. C.) Au.sup.+3 Au.sup.3+ in
soln with Red-brown solid N/A Au continues to fall addition of NaOH
formed immediately, out of soln over time (RT) Au flakes observed,
83% Ag.sup.+ Ag.sup.+ in soln at pH 4 No solid formed N/A (RT)
Ag.sup.+ Ag.sup.+ in soln at pH 4 Ag mirror forms 23% 23% Ag(s) +
67% (100.degree. C.) glucose Cu.sup.2+ Cu.sup.2+ in soln at pH 7 No
solid formed N/A (RT) Cu.sup.2+ Cu.sup.2+ in soln at pH 7 No solid
formed N/A (100.degree. C.)
[0111] Ag and Au solids formed using glucose as a reducing agent,
wherein Au required the presence of a base and Ag required high
temperatures (100.degree. C.).
[0112] 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.
* * * * *