U.S. patent application number 12/622551 was filed with the patent office on 2010-12-16 for method for recovering gold, silver, copper and iron from plasma-caused slag containing valuable metals.
This patent application is currently assigned to ATOMIC ENERGY COUNCIL-INSTITUTE OF NUCLEAR ENERGY RESEARCH. Invention is credited to Ching-Lian Chen, Ching-Hwa Lee, Wen-Cheng Lee, Kuan-Ting Liu, Shao-Wen Wu, Chen-Yu Yen.
Application Number | 20100314242 12/622551 |
Document ID | / |
Family ID | 43305472 |
Filed Date | 2010-12-16 |
United States Patent
Application |
20100314242 |
Kind Code |
A1 |
Lee; Wen-Cheng ; et
al. |
December 16, 2010 |
Method for Recovering Gold, Silver, Copper and Iron from
Plasma-Caused Slag Containing Valuable Metals
Abstract
There is disclosed an environmentally friendly method for
recovering gold, silver, copper and iron from valuable
metal-contained plasma-molten slag. At first, plasma is used to
burn the used printed circuit boards, thus producing the slag.
Then, the slag is grinded. Then, leaching, crystallization,
precipitation, replacement and electric winning are conducted to
recover gold, silver, copper and iron.
Inventors: |
Lee; Wen-Cheng; (Longtan
Shiang, TW) ; Chen; Ching-Lian; (Longtan Shiang,
TW) ; Lee; Ching-Hwa; (Longtan Shiang, TW) ;
Liu; Kuan-Ting; (Longtan Shiang, TW) ; Wu;
Shao-Wen; (Longtan Shiang, TW) ; Yen; Chen-Yu;
(Longtan Shiang, TW) |
Correspondence
Address: |
Jackson Intellectual Property Group PLLC
106 Starvale Lane
Shipman
VA
22971
US
|
Assignee: |
ATOMIC ENERGY COUNCIL-INSTITUTE OF
NUCLEAR ENERGY RESEARCH
Taoyuan
TW
|
Family ID: |
43305472 |
Appl. No.: |
12/622551 |
Filed: |
November 20, 2009 |
Current U.S.
Class: |
204/157.15 |
Current CPC
Class: |
C22B 3/065 20130101;
Y02P 10/236 20151101; C22B 7/007 20130101; Y02P 10/234 20151101;
C22B 15/0091 20130101; C22B 11/046 20130101; C22B 11/025 20130101;
C22B 7/005 20130101; Y02P 10/20 20151101; C22B 3/44 20130101; C22B
7/001 20130101; Y02P 10/214 20151101; C22B 15/0089 20130101; C22B
3/46 20130101; C22B 11/042 20130101; C22B 4/005 20130101; C22B 3/08
20130101 |
Class at
Publication: |
204/157.15 |
International
Class: |
C22B 11/00 20060101
C22B011/00; C22B 15/00 20060101 C22B015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 2, 2009 |
TW |
098111087 |
Claims
1. A method for recovering valuable metals from used printed
circuit boards comprising the steps of: providing plasma for
burning the used printed circuit boards, thus providing slag;
grinding the slag; providing a sieve with meshes of 0.149 mm for
sieving the slag, thus separating large debris larger than 0.149 mm
from small debris smaller than 0.149 mm; providing a magnet for
testing the large debris, thus separating ferromagnetic large
debris from non-ferromagnetic large debris so that the
ferromagnetic large debris can be provided to a steel-making
factory while the non-ferromagnetic large debris, which is rich in
copper, can be provided to a copper refinery; providing a magnet to
test the small debris, thus separating ferromagnetic small debris
from non-ferromagnetic small debris so that the ferromagnetic small
debris can be provided to a steel-making factory; providing 18N
sulfuric acid for leaching the non-ferromagnetic small debris,
wherein the solid/liquid ratio is retained at 10 g/50 ml, and the
temperature is kept at 70 degrees Celsius so that 90.56% of the
copper is released from the non-ferromagnetic small debris to the
sulfuric acid after 1 hour, thus separating primary
copper-contained leaching solution from primary sulfuric
acid-leached residue; retaining the copper-containing leaching
solution at 27 degrees Celsius for 48 hours for crystallization so
that 58.28% of the copper is recovered in the form of copper
sulfate crystals, thus separating the copper sulfate crystals from
optimal crystallization filtrate; replacing the copper in the
optimal crystallization filtrate with iron powder used as
replacement reagent so that 100% of the copper is recovered from
the optical crystallization filtrate when the amount of the iron
reaches 100 times of the theoretical value, thus providing copper
powder; providing 18N sulfuric acid for leaching the sulfuric
acid-leached residue again, wherein the solid/liquid ratio is
retained at 50 g/50 ml, and the temperature is kept at 70 degrees
Celsius so that 100% of the copper is released from the sulfuric
acid-leached residue to the sulfuric acid after 2 hours, thus
separating secondary copper-containing leaching solution from
secondary sulfuric acid-leached residue; replacing the copper in
the secondary copper-contained leaching solution with iron powder
used as replacement reagent so that 100% of the copper is recovered
from the secondary copper-contained leaching solution when the
amount of the iron reaches 150 times of the theoretical value, thus
providing copper powder; providing 8N nitric acid for leaching the
sulfuric acid-leached residue, wherein the solid/liquid ratio is
retained at 1 g/50 ml, and the temperature is kept at 70 degrees
Celsius so that 100% of the silver is released to the nitric acid
from the sulfuric acid-leached residue after 4 hours, thus
separating optimal silver-containing leaching solution from nitric
acid-leached residue; providing ammonia solution for adjusting the
pH of the optimal silver-contained leaching solution; providing 12N
hydrochloric acid for precipitation, wherein the ratio of the
hydrochloric acid to the silver-contained leaching solution is 1:4
so that 100% of the silver is recovered in the form of silver
chloride; providing 100% aqua liquid for leaching the nitric
acid-leached residue, wherein the ratio of the nitric acid-leached
residue to the 100% aqua liquid is 0.5 g/50 ml, and the temperature
is 70 degrees Celsius so that 100% of the gold is released to the
aqua liquid from the nitric acid-leached residue after 4 hours,
thus providing optimal gold-contained leaching solution; and
replacing the gold in the optimal gold-contained leaching solution
with zinc powder used as replacement agent, thus recovering 99.43%
of the gold from the optimal gold-contained leaching solution.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an environmentally friendly
method for recovering gold, silver, copper and iron from valuable
metal contained plasma-molten slag via plasma burning, grinding,
leaching, crystallization, precipitation, replacement and electric
winning.
DESCRIPTION OF THE RELATED ARTS
[0002] Used printed circuit boards contain valuable metals such as
silver, gold, copper and iron. If they are disposed of without
recovering the valuable metals contained, it will be a hazard to
the environment and loss of resources. Conventionally, the used
printed circuit boards can be directly crushed before the valuable
metals are recovered as disclosed in Taiwanese Patent Publication
Nos. 247281 and 36904 for example. However, it consumes excessive
energy because they contain a lot of elastic resin that is
difficultly crushed to debris. Moreover, there are problems related
to production of undesired dust and noise and wearing of
machines.
[0003] Alternatively, the conventional burning method can be used
for pretreatment. However, it takes much time and therefore
expenses a lot of energy to burn the used printed circuit boards
for low combustion efficiency.
[0004] As disclosed in Taiwanese Patent Publication No. 1268184,
the used printed circuit boards are heated to a temperature higher
than 200 degrees Celsius to melt solder on the used printed circuit
boards so that electronic parts can be removed from the used
printed circuit boards. Then, the electronic parts are submerged in
a solvent and dissolved so that the valuable metals can be
recovered.
[0005] Therefore, the present invention is intended to obviate or
at least alleviate the problems encountered in prior art.
SUMMARY OF THE INVENTION
[0006] It is the primary objective of the present invention to
provide an environmentally friendly method for recovering valuable
metals from used printed circuit boards.
[0007] To achieve the foregoing objective, in the method, plasma is
used to burn the used printed circuit boards, thus providing slag.
The slag is grinded to debris smaller than 2 mm. A sieve with
meshes of 0.149 mm is used to screen the debris into two fractions,
the larger and the smaller ones. A magnet is used to separate
ferromagnetic debris from non-ferromagnetic debris so that the
ferromagnetic debris can be provided to a steel-making factory. The
non-ferromagnetic large debris, which is rich in copper, can be
provided to a copper refinery. The non-ferromagnetic small debris,
which still contains valuable metals, can be further treated for
recovering gold, silver and copper. 18N sulfuric acid is used to
leach the debris. The solid/liquid ratio is retained at 10 g/50 ml,
and the operational temperature is kept at 70 degrees Celsius so
that 90.56% of the copper is released from the non-ferromagnetic
small debris to the sulfuric acid after 1 hour. The
copper-contained primary leaching solution is subsequently
separated from the primary sulfuric acid-leached residue and
retained at 27 degrees Celsius for 48 hours for crystallization.
58.28% of the copper is precipitated and recovered in the form of
copper sulfate crystals. The copper remained in the crystallization
filtrate is replaced with iron powder, which is used as replacement
reagent. 100% of the copper can be recovered as copper powder from
the filtrate when iron is added at 100 times of the theoretical
amount. 18N sulfuric acid is used to leach the primary sulfuric
acid-leached residue again. The solid/liquid ratio is retained at
50 g/50 ml, and the temperature is kept at 70 degrees Celsius so
that 100% of the copper is released from the primary sulfuric
acid-leached residue to the sulfuric acid after 2 hours. The
secondary copper-contained leaching solution is then separated from
the secondary sulfuric acid-leached residue. The copper in the
solution is again replaced with iron powder so that copper is
completely recovered when iron is added at 150 times of the
theoretical amount. 8N nitric acid is used to leach the secondary
sulfuric acid-leached residue, wherein the solid/liquid ratio is
retained at 1 g/50 ml, and the temperature is kept at 70 degrees
Celsius so that 100% of the silver is released to the nitric acid
from the residue after 4 hours. Then the optimal silver-contained
leaching solution is separated from the nitric acid-leached residue
and using ammonia solution to adjust the pH value to 10.
Subsequently 12N hydrochloric acid is provided for precipitation
reaction. The ratio of the hydrochloric acid to the
silver-containing leaching solution is 1:4 so that 100% of the
silver is recovered in the form of silver chloride. The nitric
acid-leached residue is then treated with 100% aqua liquid for
recovering gold. The ratio of the residue to the aqua liquid is 0.5
g/50 ml, and the temperature is kept at 70 degrees Celsius so that
100% of the gold is released to the aqua liquid from the nitric
acid-leached residue after 4 hours, thus providing optimal
gold-contained leaching solution. The solution is treated with zinc
powder, as the replacement reagent, to recover about 99.43% of the
gold from the optimal gold-contained leaching solution.
[0008] Other objectives, advantages and features of the present
invention will become apparent from the following description
referring to the attached drawings.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0009] The present invention will be described via detailed
illustration of the preferred embodiment referring to the
drawing.
[0010] FIG. 1 is a flow chart of a method for recovering valuable
metals from valuable metal-contained plasma-molten slag according
to the preferred embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0011] Referring to FIG. 1, it reveals a method for recovering
valuable metals from valuable metal-contained plasma-caused slag
according to the preferred embodiment of the present invention. At
1, the slag is collected.
[0012] At 2, the slag is screened with a sieve with meshes of 0.149
mm. Thus, large debris 21 larger than 0.149 mm in size is separated
from small debris 22 smaller than 0.149 mm in size.
[0013] At 3, the large debris 21 is tested with a magnet so that
ferromagnetic debris 31 is separated from non-ferromagnetic debris
32. The ferromagnetic debris 31 can be provided to a steel-making
factory. The non-ferromagnetic debris 32 is rich in copper and can
be provided to a copper refinery.
[0014] At 4, the small debris 22 is tested with a magnet so that
ferromagnetic debris 41 is separated from non-ferromagnetic debris
42. The ferromagnetic debris 41 can be provided to a steel-making
factory.
[0015] At 5, primary sulfuric acid leaching occurs. The
non-ferromagnetic debris 42 is leached with 18N sulfuric acid.
During the leaching, the solid/liquid ratio is retained at 10 g/50
ml, and the temperature is kept at 70 degrees Celsius. After 1 hour
of leaching, about 90.56% of the copper is released from the
non-ferromagnetic debris 42 to the sulfuric acid. Primary
copper-contained leaching solution 51 is separated from primary
sulfuric acid-leached residue 52.
[0016] At 6, the copper-contained leaching solution 51 is retained
at 27 degrees Celsius for 48 hours for crystallization. Thus,
58.28% of the copper is recovered in the form of copper sulfate
crystals 61. The copper sulfate crystals 61 are separated from
optimal crystallization filtrate 62.
[0017] At 7, the copper in the optimal crystallization filtrate 62
is replaced with iron powder that is used as replacement reagent 7.
When the amount of the iron reaches 100 times of the theoretical
value, 100% of the copper is recovered from the optical
crystallization filtrate 62. Copper powder 71 is recovered.
[0018] At 8, secondary sulfuric acid leaching occurs. The sulfuric
acid-leached residue 52 is leached with 18N sulfuric acid again.
During the leaching, the solid/liquid ratio is retained at 50 g/50
ml, and the temperature is kept at 70 degrees Celsius. After 2
hours of leaching, about 100% of the copper is released from the
sulfuric acid-leached residue 52 to the sulfuric acid. Then,
secondary copper-contained leaching solution 81 is separated from
secondary sulfuric acid-leached residue 82.
[0019] At 9, the copper in the secondary copper-contained leaching
solution 81 is replaced with iron powder that is used as
replacement reagent 9. When the amount of the iron reaches 150
times of the theoretical value, 100% of the copper is recovered
from the secondary copper-contained leaching solution 81. Copper
powder 91 is recovered.
[0020] At 10, the sulfuric acid-leached residue 82 is leached with
8N nitric acid. During the leaching, the solid/liquid ratio is
retained at 1 g/50 ml, and the temperature is kept at 70 degrees
Celsius. After 4 hours of leaching, about 100% of the silver is
released to the nitric acid from the sulfuric acid-leached residue
82. Optimal silver-contained leaching solution 101 is separated
from nitric acid-leached residue 102.
[0021] At 11, the pH of the optimal silver-contained leaching
solution 101 is adjusted with ammonia solution.
[0022] At 12, 12N hydrochloric acid is used as precipitating agent.
During the precipitation, the ratio of the hydrochloric acid to the
silver-contained leaching solution 101 is 1:4. Thus, 100% of the
silver is recovered in the form of silver chloride 121.
[0023] At 13, the nitric acid-leached residue 102 is leached with
100% aqua liquid. During the leaching, the ratio of the nitric
acid-leached residue 102 to the 100% aqua liquid is 0.5 g/50 ml.
The temperature is 70 degrees Celsius. After 4 hours, 100% of the
gold is released to the aqua liquid from the nitric acid-leached
residue 102, thus providing optimal gold-contained leaching
solution 131.
[0024] At 14, the gold in the optimal gold-contained leaching
solution 131 is replaced with zinc powder that is used as
replacement agent. Thus, 99.43% of the gold is recovered from the
optimal gold-contained leaching solution 131. Gold 141 is
collected.
[0025] The method of the present invention exhibits several
advantages. Firstly, gold, silver, copper and iron are rapidly
recovered from used printed circuit boards. Therefore, the valuable
metals can be processed in refineries and reused to reduce the
waste of metals. Secondly, hazardous materials produced during the
recovering of the valuable metals are reduced. Therefore, the
hazard to the environment and human bodies is reduced.
[0026] The present invention has been described via the detailed
illustration of the preferred embodiment. Those skilled in the art
can derive variations from the preferred embodiment without
departing from the scope of the present invention. Therefore, the
preferred embodiment shall not limit the scope of the present
invention defined in the claims.
[0027] The present invention has been described via the detailed
illustration of the preferred embodiment. Those skilled in the art
can derive variations from the preferred embodiment without
departing from the scope of the present invention. Therefore, the
preferred embodiment shall not limit the scope of the present
invention defined in the claims.
* * * * *