Title of Invention	AN IMPROVED PROCESS FOR EXTRACTION OF COPPER, SELENIUM, TELLURIUM AND GOLD FROM ANODE SLIME OF COPPER ELECTROREFINING PLANT
Abstract	An improved process for extraction of copper, selenium, tellurium and gold from anode slime of copper electrorefining plant which comprises: (i) grinding the anode slime of composition such as herein described to 140 - 160 µm in size, (ii) characterised in that adding sulphuric acid and additive selected from sodium chloride, manganese dioxide and mixture thereof to said ground anode slime with solid to liquid ratio in the range of l:7to 1:12, (iii) stirring the solution obtained in step (ii) for a period of 4 - 6 hours in the temperature range of 30-80°C, (iv) filtering the leach slurry obtained in step (iii), (v) recovering copper, selenium, tellurium and gold from the said filtrate by known method.

Title of Invention

AN IMPROVED PROCESS FOR EXTRACTION OF COPPER, SELENIUM, TELLURIUM AND GOLD FROM ANODE SLIME OF COPPER ELECTROREFINING PLANT

Abstract

An improved process for extraction of copper, selenium, tellurium and gold from anode slime of copper electrorefining plant which comprises: (i) grinding the anode slime of composition such as herein described to 140 - 160 µm in size, (ii) characterised in that adding sulphuric acid and additive selected from sodium chloride, manganese dioxide and mixture thereof to said ground anode slime with solid to liquid ratio in the range of l:7to 1:12, (iii) stirring the solution obtained in step (ii) for a period of 4 - 6 hours in the temperature range of 30-80°C, (iv) filtering the leach slurry obtained in step (iii), (v) recovering copper, selenium, tellurium and gold from the said filtrate by known method.

Full Text	The present invention relates to an improved process for extraction of copper, selenium, tellurium and gold from anode slime of copper electrorefining plant. This invention is particularly relates to an improved leaching process of anode slime of copper electrorefining plant in sulphuric acid medium for extraction of valuable metals like copper, selenium, tellurium and gold. Anode slime is the insoluble product deposited at the bottom of the electrorefining tank during the electrorefining of copper. It contains valuable elements like, Cu, Ni, Se, Te, Ag, Au and trace amounts of platinum group metals. The anode slime is periodically collected from copper electrorefining tank and is processed for the recovery of the metals and metalloids. It generally contains copper sulphate, nickel oxide, copper selenide, copper telluride, silver selenide, gold telluride, silica etc. Depending upon the charged materials, the anode slime composition varies from refinery to refinery, and based on the composition and morphology of slime, various processing routes have been developed. These include (1) Pyrometallurgical processes, (2) Pyro-hydrometallurgical processes and (3) Hydrometallurgical processes. Several investigators have studied pyrometallurgical processes for the extraction of valuable elements from the anode slime. Reference may be made to I.E. Hoffmann, J. Met., Aug., 1990, pp.50-54, wherein it is described that the classical treatment of anode slime involves smelting in dore furnace with a siliceous flux to produce a slag and a metal/matte phase. The metal/matte phase is subsequently oxidised using air, sodium carbonate and sodium nitrate to recover selenium, tellurium, copper and finally producing silver bullion. However, the process suffers from various drawbacks like large in-process inventories of precious metals and recycling of precious metals in the slag along with high energy consumption and potential environmentally objectionable emission of selenium and tellurium due to smelting. Some pyro-hydrometallurgical routes have also been developed. The pyrometallurgical pre-treatments are soda roasting, sulphation roasting, oxidation roasting etc. After the pre-treatments, the reacted slimes are generally leached in dilute acid solution. Reference may be made to W. Charles Cooper, the treatment of copper refinery anode slimes, J. Met., Aug. 1990, pp.45-49 wherein all the above processes have been described. Combined hydro-pyrometallurgical processes have also been reported in the literature. Reference may be made to O. Hyvarinen, E. Rosenberg and L. Lindroos in: V. Kudryk, D. A. Corrigan, W. W. Liang (Eds), Precious Metals: Mining, Extraction and Processing, Metallurgical Society of AIME, Warrendale, Pennsylvania, 1984, pp.537-548, wherein it has been described that in the first stage decopperizing and denickelization is done in dilute and concentrated sulphuric acids respectively. This is followed by roasting of the leach residue at about 600°C for selenium recovery. The resultant selenium free slime is smelted in dore furnace using soda and borax for the recovery of the precious metals. It has been noted that in all the above mentioned processes, selenium is recovered either in roasting or smelting step. Therefore, sophisticated and highly efficient scrubber to convert the volatile selenium to selenious acid is required. Also any emission of selenium gas is health hazardous. For the above mentioned reasons, recovery of valuable elements from anode slime by hydrometallurgical treatment was long been felt. Reference may be made to J. E. Hoffman, J. Met., Aug. 1990, pp.50-54 wherein hydrometallurgical processes have been described to recover valuable elements from slime using sulphuric acid, hydrochloric acid and ammonia as lixiviants. However none of these leachants recovered the elements satisfactorily. Reference may also be made to W. K. Wang, Y. C. Hoh, W. S. Chuang, and I. S. Shaw, Hydrometallurgical process for recovering precious metals from anode slime, U.S.Patent 4,293,332, Oct. 6, 1981, wherein nitric acid leaching of de-copperized slime and precipitation of the dissolved silver as silver chloride has been proposed as initial steps in slime treatment. However, use of nitric acid creates corrosion and pollution problems. Another hydrometallurgical process at ambient temperature and pressure is wet chlorination. This process is one of the promising processes since the separation of silver and gold can be carried out at the early stage of the processing, which lowers the process inventory of the precious metals. Good recoveries of all the valuable elements present in the anode slime can also be achieved in this process. Reference may be made to J. E. Hoffman, and D. C. Cusanelli, Processing for chlorination of electrolytic copper refinery slimes, U.S. Patent 3,249,399, May 3, 1966, wherein chlorine leaching of anode slime has been carried out using chlorine - water, hydrogen peroxide - hydrochloric acid or sodium chlorate -hydrochloric acid leachants. Good recoveries of the valuable elements have been achieved except silver, which precipitate as silver chloride in the chloride medium. Silver is recovered from the residue by ammonia leaching. Other elements from the leach solution is recovered by precipitation routes. The main drawback of the process is the use of costly reagents like hydrogen peroxide and sodium chlorate, which can not be recovered from the leach solution. This may affect the economics of the process. Further, use of hydrochloric acid which is corrosive in nature, impose the restriction on materials of construction and create pollution problem with acid fumes. The main object of the present invention is to provide an improved process for the extraction of copper, selenium, tellurium and gold from anode slime of copper electrorefming plant, which obviates the drawbacks as detailed above. Another object of the present invention is to provide an improved leaching process of anode slime of copper electrorefming plant in sulphuric acid medium for extraction of valuable metals like copper, selenium, tellurium and gold. In the process of present invention anode slime is leached in sulphuric acid medium using sodium chloride and manganese dioxide additives. As such sulphuric acid can not leach appreciable amounts of copper, selenium, tellurium, silver and gold from the anode slime. The addition of sodium chloride and manganese dioxide in sulphuric acid generates chlorine. 2NaCl + MnO2 + 2H2SO4 → Na2SO4 + MnSO4 + 2H2O + C12 The chlorine generated reacts with the valuable elements in anode slime and produce soluble salts and acids except silver chloride, which precipitates. CuSe + 3C12 + 3H2O → CuCl2 + H2SeO3 + 4HC1 CuTe + 3C12 + 3H2O → CuCh + H2TeO3 + 4HC1 Ag2Se + 3C12 + 3H2O → 2AgCl + H2SeO3 + 4HC1 Au + 3C12 → 2AuCl3 AuCb + HCl^HAuCl4 Hydrochloric acid produced in the reactions reacts again with manganese dioxide to produce more chlorine, which further reacts with anode slime to dissolve more elements from anode slime as shown above. MnO2 + 4HC1 •> MnCl2 + 2H2O + C12 For the recovery of silver, reference may be made to J. E. Hoffman, J. Met., Aug. 1990, pp 50-54 wherein chlorine leached residue is treated with ammonium hydroxide to produce pure ammoniacal solution of silver chloride. The filtered solution is neutralised by sulphuric acid and pure silver chloride is precipitated. Accordingly the present invention provides an improved process for extraction of copper, selenium, tellurium and gold from anode slime of copper electrorefining plant which comprises: (i) grinding the anode slime of composition such as herein described to 140 - 160 µm in size, (ii) characterised in that adding sulphuric acid and additive selected from sodium chloride, manganese dioxide and mixture thereof to said ground anode slime with solid to liquid ratio in the range of l:7to 1:12, (iii) stirring the solution obtained in step (ii) for a period of 4 - 6 hours in the temperature rangeof 30-80°C, (iv) filtering the leach slurry obtained in step (iii), (v) recovering copper, selenium, tellurium and gold from the said filtrate by known method. In an embodiment of the of the invention the anode slime employed may have composition range: Cu 10-14 Wt% Ni 30-40Wt% Se 8-12 Wt% Te 2-5 Wt% Ag 1-2 Wt% Au 0.1-0.2Wt% The sulphuric acid used for leaching of anode slime may be of commercial grade and sulphuric acid solution may vary from 10-30 vol.% The sodium chloride used as additive in the sulphuric acid leaching of anode slime may be commercial grade and addition may be 0 - 90 Wt% of anode slime used. The manganese dioxide used as additive in the sulphuric acid leaching of anode slime may be commercial grade and addition may be 0 - 90 Wt% of anode slime used. According to a feature of this invention, the leach liquor produced on leaching in sulphuric acid medium with sodium chloride and manganese dioxide additives contains copper, selenium, tellurium and gold and leached residue contains silver chloride, which can be separated and recovered by known methods. By the process of present invention elements recovered in the leach solution are Cu = 95%, Se = 80%, Te = 80% and Au = 80%. Novelty of the present invention is the addition of manganese dioxide and sodium chloride in the sulphuric acid leaching of copper electrorefining anode slime for recovery of copper, selenium, tellurium and gold. The following examples are given by way of illustration of the present invention and therefore should not be construed to limit the scope of the present invention. EXAMPLE-I 5 grams of ground anode slime was leached in 20 vol% sulphuric acid at 1:10 solid to liquid ratio and stirred moderately for 4 h at 70°C. Then the solids were separated from the solution by filtration and was analysed for metals. The recoveries obtained from the solution analysis were found to be Cu - 55%, Te - 6%, Se - 5%, Ag - trace, Au - trace. EXAMPLE-II 5 grams of ground anode slime was leached in a solution containing 20 vol.% sulphuric acid with 50 Wt.% of manganese dioxide addition at 1:10 solid to liquid ratio and stirred for 4 h at 80°C. Then the solids were separated from the solution by filtration and was analysed for elements. The recoveries obtained from the solution analysis were found to be Cu - 78%, Se - 37%, Te - 66%, Ag - 22% and Au - trace. EXAMPLE-III. 10 grams of ground anode slime was leached in a solution containing 20 vol.% sulphuric acid with 50 Wt.% manganese dioxide and 20% Wt.% sodium chloride additives at 1:10 solid : liquid ratio and stirred moderately for 4 h at 80°C. Then the solids were separated from the solution and the solution was analysed for elements. The recoveries obtained from the solution analysis were found to be Cu - 95%, Se - 78%, Te -73%, Ag - trace and Au -67%. EXAMPLE-IV. 5 grams of ground anode slime was leached in a solution containing 10 vol.% sulphuric acid with 50 Wt% manganese dioxide and 90 Wt% sodium chloride additives at 1:10 solid:liquid ratio and stirred moderately for 4 h at 80°C. Then the solids were separated from the solution and the solution was analyzed for elements. The recoveries obtained from the solution analysis were found to be Cu - 87%, Se - 78 %, Te - 79 %, Ag - trace, Au -78%. EXAMPLE-V. 5 grams of ground anode slime was leached in a solution containing 20 Vol% sulphuric acid with 50 Wt% manganese dioxide and 90 Wt% sodium chloride additives at 1:10 solid to liquid ratio and stirred moderately for 6 h at 30°C. Then the solids were separated from the solution by filtration and the solution was analysed for elements. The recoveries obtained from the solution analysis were found to be Cu - 85%, Se - 80%, Te -79%, Au - 80%. EXAMPLE-VI. 10 grams of ground anode slime was leached in a solution containing 20 Vol% sulphuric acid with 75Wt% manganese dioxide and 90 Wt% sodium chloride additives at 1:10 solid to liquid ratio and stirred moderately for 6 h at 80° C. Then the solids were separated from the solution by filtration and the solution was analysed for elements. The recoveries obtained from the solution analysis were found to be Cu - 85%, Se - 79%, Te -80%, Au- 80%. The main advantages of the present invention are: (i) In the present invention consumption of energy is less than the conventional processes as it excludes any pyrometallurgical steps like roasting and smelting, (ii) The process is not involved in the evolution of hazardous selenium and tellurium gases as the pyrometallurgical steps have been removed, (iii) In the present invention sulphuric acid is used as the leaching medium and hence the process is technically feasible due to less corrosion problem, (iv) The present invention has resulted in recoveries about 80% of the valuable element such as copper, selenium, tellurium and gold. (v) Silver can be recovered from the leached residue by known method, (vi) In the present invention the capital investment cost of the process is less than the existing pyro-hydrometallurgical or hydro-pyrometallurgical processes. We claim: 1. An improved process for extraction of copper, selenium, tellurium and gold from anode slime of copper electrorefming plant which comprises: (i) grinding the anode slime of composition such as herein described to 140 - 160 µm in size, (ii) characterised in that adding sulphuric acid and additive selected from sodium chloride, manganese dioxide and mixture thereof to said ground anode slime with solid to liquid ratio in the range of 1:7to 1:12, (iii) stirring the solution obtained in step (ii) for a period of 4 - 6 hours in the temperature rangeof 30-80°C, (iv) filtering the leach slurry obtained in step (iii), (v) recovering copper, selenium, tellurium and gold from the said filtrate by known method. 2. An improved process as claimed in claim 1 wherein sulphuric acid used for leaching of anode slime is of commercial grade and strength of sulphuric acid solution used is in the range of 10-30 vol%. 3. An improved process as claimed in claims 1 to 2 wherein the manganese dioxide used as additive in the sulphuric acid leaching of anode slime is commercial grade and used amounts are in the range of 0-90 Wt%. 4. An improved process as claimed in claims 1 to 3 wherein the sodium chloride used as additive in the sulphuric acid leaching of anode slime is of commercial grade and used amounts are in the range of 0-90 Wt%. 5. An improved process for extraction of copper, selenium, tellurium and gold from anode slime of copper electrorefming plant substantially as herein described with reference to the examples.

Full Text

The present invention relates to an improved process for extraction of copper, selenium, tellurium and gold from anode slime of copper electrorefining plant. This invention is particularly relates to an improved leaching process of anode slime of copper electrorefining plant in sulphuric acid medium for extraction of valuable metals like copper, selenium, tellurium and gold.
Anode slime is the insoluble product deposited at the bottom of the electrorefining tank during the electrorefining of copper. It contains valuable elements like, Cu, Ni, Se, Te, Ag, Au and trace amounts of platinum group metals.
The anode slime is periodically collected from copper electrorefining tank and is processed for the recovery of the metals and metalloids. It generally contains copper sulphate, nickel oxide, copper selenide, copper telluride, silver selenide, gold telluride, silica etc. Depending upon the charged materials, the anode slime composition varies from refinery to refinery, and based on the composition and morphology of slime, various processing routes have been developed. These include (1) Pyrometallurgical processes, (2) Pyro-hydrometallurgical processes and (3) Hydrometallurgical processes.
Several investigators have studied pyrometallurgical processes for the extraction of valuable elements from the anode slime. Reference may be made to I.E. Hoffmann, J. Met., Aug., 1990, pp.50-54, wherein it is described that the classical treatment of anode slime involves smelting in dore furnace with a siliceous flux to produce a slag and a metal/matte phase. The metal/matte phase is subsequently oxidised using air, sodium carbonate and sodium nitrate to recover selenium, tellurium, copper and finally producing silver bullion. However, the process suffers from various drawbacks like large in-process inventories of precious metals and recycling of precious metals in the slag along with high energy consumption and potential environmentally objectionable emission of selenium and tellurium due to smelting.
Some pyro-hydrometallurgical routes have also been developed. The pyrometallurgical pre-treatments are soda roasting, sulphation roasting, oxidation roasting etc. After the pre-treatments, the reacted slimes are generally leached in dilute acid solution. Reference may be made to W. Charles Cooper, the treatment of copper refinery anode slimes, J. Met., Aug. 1990, pp.45-49 wherein all the above processes have been described. Combined hydro-pyrometallurgical processes have also been reported in the literature. Reference may be made to O. Hyvarinen, E. Rosenberg and L. Lindroos in: V. Kudryk, D. A.
Corrigan, W. W. Liang (Eds), Precious Metals: Mining, Extraction and Processing, Metallurgical Society of AIME, Warrendale, Pennsylvania, 1984, pp.537-548, wherein it has been described that in the first stage decopperizing and denickelization is done in dilute and concentrated sulphuric acids respectively. This is followed by roasting of the leach residue at about 600°C for selenium recovery. The resultant selenium free slime is smelted in dore furnace using soda and borax for the recovery of the precious metals. It has been noted that in all the above mentioned processes, selenium is recovered either in roasting or smelting step. Therefore, sophisticated and highly efficient scrubber to convert the volatile selenium to selenious acid is required. Also any emission of selenium gas is health hazardous.
For the above mentioned reasons, recovery of valuable elements from anode slime by hydrometallurgical treatment was long been felt. Reference may be made to J. E. Hoffman, J. Met., Aug. 1990, pp.50-54 wherein hydrometallurgical processes have been described to recover valuable elements from slime using sulphuric acid, hydrochloric acid and ammonia as lixiviants. However none of these leachants recovered the elements satisfactorily. Reference may also be made to W. K. Wang, Y. C. Hoh, W. S. Chuang, and I. S. Shaw, Hydrometallurgical process for recovering precious metals from anode slime, U.S.Patent 4,293,332, Oct. 6, 1981, wherein nitric acid leaching of de-copperized slime and precipitation of the dissolved silver as silver chloride has been proposed as initial steps in slime treatment. However, use of nitric acid creates corrosion and pollution problems.
Another hydrometallurgical process at ambient temperature and pressure is wet chlorination. This process is one of the promising processes since the separation of silver and gold can be carried out at the early stage of the processing, which lowers the process inventory of the precious metals. Good recoveries of all the valuable elements present in the anode slime can also be achieved in this process. Reference may be made to J. E. Hoffman, and D. C. Cusanelli, Processing for chlorination of electrolytic copper refinery slimes, U.S. Patent 3,249,399, May 3, 1966, wherein chlorine leaching of anode slime has been carried out using chlorine - water, hydrogen peroxide - hydrochloric acid or sodium chlorate -hydrochloric acid leachants. Good recoveries of the valuable elements have been achieved except silver, which precipitate as silver chloride in the chloride medium. Silver is recovered from the residue by ammonia leaching. Other elements from the leach solution is recovered by precipitation routes. The main drawback of the process is the use of costly reagents like hydrogen peroxide and sodium chlorate, which can not be recovered from the leach solution.
This may affect the economics of the process. Further, use of hydrochloric acid which is corrosive in nature, impose the restriction on materials of construction and create pollution problem with acid fumes.
The main object of the present invention is to provide an improved process for the extraction of copper, selenium, tellurium and gold from anode slime of copper electrorefming plant, which obviates the drawbacks as detailed above.
Another object of the present invention is to provide an improved leaching process of anode slime of copper electrorefming plant in sulphuric acid medium for extraction of valuable metals like copper, selenium, tellurium and gold.
In the process of present invention anode slime is leached in sulphuric acid medium using sodium chloride and manganese dioxide additives. As such sulphuric acid can not leach appreciable amounts of copper, selenium, tellurium, silver and gold from the anode slime. The addition of sodium chloride and manganese dioxide in sulphuric acid generates chlorine.
2NaCl + MnO2 + 2H2SO4 → Na2SO4 + MnSO4 + 2H2O + C12
The chlorine generated reacts with the valuable elements in anode slime and produce soluble salts and acids except silver chloride, which precipitates.
CuSe + 3C12 + 3H2O → CuCl2 + H2SeO3 + 4HC1
CuTe + 3C12 + 3H2O → CuCh + H2TeO3 + 4HC1
Ag2Se + 3C12 + 3H2O → 2AgCl + H2SeO3 + 4HC1
Au + 3C12 → 2AuCl3
AuCb + HCl^HAuCl4
Hydrochloric acid produced in the reactions reacts again with manganese dioxide to produce more chlorine, which further reacts with anode slime to dissolve more elements from anode slime as shown above.
MnO2 + 4HC1 •> MnCl2 + 2H2O + C12
For the recovery of silver, reference may be made to J. E. Hoffman, J. Met., Aug. 1990, pp 50-54 wherein chlorine leached residue is treated with ammonium hydroxide to produce pure ammoniacal solution of silver chloride. The filtered solution is neutralised by sulphuric acid and pure silver chloride is precipitated.
Accordingly the present invention provides an improved process for extraction of copper, selenium, tellurium and gold from anode slime of copper electrorefining plant which comprises:
(i) grinding the anode slime of composition such as herein described to 140 - 160 µm in size,
(ii) characterised in that adding sulphuric acid and additive selected from sodium chloride, manganese dioxide and mixture thereof to said ground anode slime with solid to liquid ratio in the range of l:7to 1:12,
(iii) stirring the solution obtained in step (ii) for a period of 4 - 6 hours in the temperature rangeof 30-80°C,
(iv) filtering the leach slurry obtained in step (iii), (v) recovering copper, selenium, tellurium and gold from the said filtrate by known method.
In an embodiment of the of the invention the anode slime employed may have
composition range: Cu 10-14 Wt%
Ni 30-40Wt% Se 8-12 Wt% Te 2-5 Wt% Ag 1-2 Wt% Au 0.1-0.2Wt%
The sulphuric acid used for leaching of anode slime may be of commercial grade and sulphuric acid solution may vary from 10-30 vol.%
The sodium chloride used as additive in the sulphuric acid leaching of anode slime may be commercial grade and addition may be 0 - 90 Wt% of anode slime used.
The manganese dioxide used as additive in the sulphuric acid leaching of anode slime may be commercial grade and addition may be 0 - 90 Wt% of anode slime used.
According to a feature of this invention, the leach liquor produced on leaching in sulphuric acid medium with sodium chloride and manganese dioxide additives contains copper, selenium, tellurium and gold and leached residue contains silver chloride, which can be separated and recovered by known methods. By the process of present invention elements recovered in the leach solution are Cu = 95%, Se = 80%, Te = 80% and Au = 80%.
Novelty of the present invention is the addition of manganese dioxide and sodium chloride in the sulphuric acid leaching of copper electrorefining anode slime for recovery of copper, selenium, tellurium and gold.
The following examples are given by way of illustration of the present invention and therefore should not be construed to limit the scope of the present invention.
EXAMPLE-I
5 grams of ground anode slime was leached in 20 vol% sulphuric acid at 1:10 solid to liquid ratio and stirred moderately for 4 h at 70°C. Then the solids were separated from the solution by filtration and was analysed for metals. The recoveries obtained from the solution analysis were found to be Cu - 55%, Te - 6%, Se - 5%, Ag - trace, Au - trace.
EXAMPLE-II
5 grams of ground anode slime was leached in a solution containing 20 vol.% sulphuric acid with 50 Wt.% of manganese dioxide addition at 1:10 solid to liquid ratio and stirred for 4 h at 80°C. Then the solids were separated from the solution by filtration and was analysed for elements. The recoveries obtained from the solution analysis were found to be Cu - 78%, Se - 37%, Te - 66%, Ag - 22% and Au - trace.
EXAMPLE-III.
10 grams of ground anode slime was leached in a solution containing 20 vol.% sulphuric acid with 50 Wt.% manganese dioxide and 20% Wt.% sodium chloride additives at 1:10 solid : liquid ratio and stirred moderately for 4 h at 80°C. Then the solids were separated from the solution and the solution was analysed for elements. The recoveries obtained from the solution analysis were found to be Cu - 95%, Se - 78%, Te -73%, Ag - trace and Au -67%.
EXAMPLE-IV.
5 grams of ground anode slime was leached in a solution containing 10 vol.% sulphuric acid with 50 Wt% manganese dioxide and 90 Wt% sodium chloride additives at 1:10 solid:liquid ratio and stirred moderately for 4 h at 80°C. Then the solids were separated from the solution and the solution was analyzed for elements. The recoveries obtained from the solution analysis were found to be Cu - 87%, Se - 78 %, Te - 79 %, Ag - trace, Au -78%.
EXAMPLE-V.
5 grams of ground anode slime was leached in a solution containing 20 Vol% sulphuric acid with 50 Wt% manganese dioxide and 90 Wt% sodium chloride additives at 1:10 solid to liquid ratio and stirred moderately for 6 h at 30°C. Then the solids were separated from the solution by filtration and the solution was analysed for elements. The recoveries obtained from the solution analysis were found to be Cu - 85%, Se - 80%, Te -79%, Au - 80%.
EXAMPLE-VI.
10 grams of ground anode slime was leached in a solution containing 20 Vol% sulphuric acid with 75Wt% manganese dioxide and 90 Wt% sodium chloride additives at 1:10 solid to liquid ratio and stirred moderately for 6 h at 80° C. Then the solids were separated from the solution by filtration and the solution was analysed for elements. The recoveries obtained from the solution analysis were found to be Cu - 85%, Se - 79%, Te -80%, Au- 80%.
The main advantages of the present invention are:
(i) In the present invention consumption of energy is less than the conventional processes
as it excludes any pyrometallurgical steps like roasting and smelting, (ii) The process is not involved in the evolution of hazardous selenium and tellurium
gases as the pyrometallurgical steps have been removed, (iii) In the present invention sulphuric acid is used as the leaching medium and hence the
process is technically feasible due to less corrosion problem, (iv) The present invention has resulted in recoveries about 80% of the valuable element
such as copper, selenium, tellurium and gold.
(v) Silver can be recovered from the leached residue by known method, (vi) In the present invention the capital investment cost of the process is less than the
existing pyro-hydrometallurgical or hydro-pyrometallurgical processes.

We claim:
1. An improved process for extraction of copper, selenium, tellurium and gold from anode
slime of copper electrorefming plant which comprises:
(i) grinding the anode slime of composition such as herein described to 140 - 160 µm in
size,
(ii) characterised in that adding sulphuric acid and additive selected from sodium chloride,
manganese dioxide and mixture thereof to said ground anode slime with solid to liquid ratio
in the range of 1:7to 1:12,
(iii) stirring the solution obtained in step (ii) for a period of 4 - 6 hours in the temperature
rangeof 30-80°C,
(iv) filtering the leach slurry obtained in step (iii),
(v) recovering copper, selenium, tellurium and gold from the said filtrate by known method.
2. An improved process as claimed in claim 1 wherein sulphuric acid used for leaching of
anode slime is of commercial grade and strength of sulphuric acid solution used is in
the range of 10-30 vol%.
3. An improved process as claimed in claims 1 to 2 wherein the manganese dioxide used
as additive in the sulphuric acid leaching of anode slime is commercial grade and used
amounts are in the range of 0-90 Wt%.
4. An improved process as claimed in claims 1 to 3 wherein the sodium chloride used as additive
in the sulphuric acid leaching of anode slime is of commercial grade and used amounts are in
the range of 0-90 Wt%.
5. An improved process for extraction of copper, selenium, tellurium and gold from anode slime
of copper electrorefming plant substantially as herein described with reference to the
examples.

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Patent Number

226232

Indian Patent Application Number

55/DEL/2002

PG Journal Number

01/2009

Publication Date

02-Jan-2009

Grant Date

12-Dec-2008

Date of Filing

25-Jan-2002

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	JHUMKI HAIT	NATIONAL MATALLURGICAL LABORATORY, JAMSHEDPUR, JHARKHAND INDIA.
2	RANAJIT KUMAR JANA	NATIONAL MATALLURGICAL LABORATORY, JAMSHEDPUR, JHARKHAND INDIA.
3	VINAY KUMAR	NATIONAL MATALLURGICAL LABORATORY, JAMSHEDPUR, JHARKHAND INDIA.

PCT International Classification Number

C22B 3/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA