Title of Invention	"AN IMPROVED FOR THE PREPARATION OF COPPER AND NICKEL POWDERS FROM COPPER BLEED STREAM "
Abstract	An improved process for preparation of copper and nickel powder from copper bleed stream by partially decopperising the sulphate phase said copper bleed stream containing polymetallic at a current density of 150 to 300 A/m2 by electrolysis to reduce copper level equal to nickel, separating the mixed copper and nickel sulphate phases from rest of the solution obtained by known methods to obtain crystallise mixed sulphates of copper and nickel phases, leaching the said mixed copper and nickel sulphate phases in aqueous media followed by dilute sulphuric acid at a temperature of 30-100°C for a period of 1 to 8 hrs, reducing the resultant solution obtained by hydrogen gas to produce copper powder, purifying the copper depleted solution obtained, reducing the said purified copper depleted solution by hydrogen gas to produce nickel powder at a temperature of 140- 250 o C for 15-120 minutes with stirring and washing and drying the said copper powder for Powder Metallurgical applications.

Title of Invention

"AN IMPROVED FOR THE PREPARATION OF COPPER AND NICKEL POWDERS FROM COPPER BLEED STREAM "

Abstract

An improved process for preparation of copper and nickel powder from copper bleed stream by partially decopperising the sulphate phase said copper bleed stream containing polymetallic at a current density of 150 to 300 A/m2 by electrolysis to reduce copper level equal to nickel, separating the mixed copper and nickel sulphate phases from rest of the solution obtained by known methods to obtain crystallise mixed sulphates of copper and nickel phases, leaching the said mixed copper and nickel sulphate phases in aqueous media followed by dilute sulphuric acid at a temperature of 30-100°C for a period of 1 to 8 hrs, reducing the resultant solution obtained by hydrogen gas to produce copper powder, purifying the copper depleted solution obtained, reducing the said purified copper depleted solution by hydrogen gas to produce nickel powder at a temperature of 140- 250 o C for 15-120 minutes with stirring and washing and drying the said copper powder for Powder Metallurgical applications.

Full Text	The present invention relates to an improved process for the preparation of copper and nickel powder from copper bleed stream. The invention particularly relates to selectively producing copper and nickel powder by reducing copper level equal to nickel, separating mixed copper and nickel solution followed by hydrogen reduction of its mixed sulphate solution. Copper bleed stream is produced in the processing of sea nodules by roast-ammonia leach - solvent extraction - electrowinning route, for controlling metallic impurities in the copper electrolysis. This solution consists of 16-20 g/L Ni and 35-45 g/L Cu besides 150-200 g/L H2SO4 and some other impurities which needs to be processed to recover valuable metals viz. nickel and copper. Producing nickel and copper powder from this solution will thus be the high value products which have specific demands and can be used in powder metallurgical (P/M) applications to make important components. Copper and nickel powders can also be prepared from the copper bleed stream of copper smelters. Besides, acidic and ammoniacal leach liquors of several lean grade and complex ores containing copper and nickel can be suitably processed to produce high value products. As such no attempt appears to be made to process copper bleed stream produced in the processing of sea nodules. The known literature on the processing of sea nodules often shows the separation and recovery of copper, nickel and cobalt from the ammoniacal / sulphate / chloride leach solutions without mentioning the metal recovery (Cu and Ni) from the bleed solutions (Han, KN, Trans. HM, 51(1), 1998, p.55-67). There are however, a number of literature reports on the processing of copper bleed streams of copper smelters. Reference may be made to Havlik et al (Havlik, T, Skrobian, M, Kammel, R, Curilla J and Cmorejova, D, Hydrometallurgy, 41, 1996, p.79-88) and Nagai et al (Nagai, T, Zaki, NY and Kobayashi, MMIJ, L-l, 1976, p. 1-4) wherein the copper bleed stream of copper smelter is subjected to a number of cumbersome steps such as (i) decopperisation to remove copper as poor quality nodular sheet (99.6% purity) for recharging to the smelter, (ii) evaporation / crystallisation of decopperised nickel sulphate solution to produce impure nickel sulphate and recycling the mother liquor to electrolysis section for acid make-up, (iii) purification of nickel sulphate by hydrometallurgical process, and (iv) crystallisation of nickel sulphate. The drawbacks are production of poor quality copper, recycling back of this copper to smelter thereby reducing the productivity, high-energy requirement, production of off-grade nickel sulphate crystal, environmental problems due to evolution of abnoxious arsine gasduring decopperisation etc. Reference may be made to Toyabe, K, Segawa, C and Sato H (In Proc. Electrorefining and winning of copper, 116 th Annual Meeting, Denver, Colorado, 1987, AIME Perm., p.99-116) and Shibata, T, Hashivchi, M and Kato, T, (116 th Annual Meeting, Dever, Colorado, 1987, AIME Perm., p.l 17-128) wherein the process is based on selective removal of Sb and Bi from electrolyte by adsorption on carbon or chelating resin and producing nickel sulphate crystals after removal of arsenic in deccopperisation step. In yet another process developed by Shibayama, R and Nagai, T (ISEC 1990, p. 1193-1198), chelating ion-exchange resin in combination with conventional process is used to recover copper and nickel cathodes/ sulphates. A process described by Abhishev, DN and Stryapkov, AV (ISEC'88, 1988, p.305-307) uses an alcohol for acid extraction and naphthenic acid to separate nickel and copper producing their sulphates. The drawbacks of the above processes are the involvement of very large number of processing steps and separation of individual components such as sulphuric acid, copper and nickel, besides producing metal salts or cathodes of lower return and payback. Reference may be made to Togashi, R and Nagai, T (Hydrometallurgy, 11, 1983, p. 149-163) wherein production of copper powder by hydrogen reduction from copper bleed stream with above 100 g/L sulphuric acid resulted in poor quality powder at higher depletion level. The drawbacks are removal of arsenic from the bleed stream, presence of bismuth ions for effective reduction of copper and need to purify electrolyte by solvent extraction. There are known processes to produce copper and nickel powder by hydrogen reduction from the leach liquors of their respective ores. Reference may be made to US Patent 2,7976,342 (1957) wherein copper precipitation is followed with modification for other metals as well. Reference may be made to US Patent 332, 679 (1973) wherein attempts had been made to the continuous preparation of metal powders by hydrogen reduction from the leach solutions of metals from their ores. The main requirements of producing metal powders are purity of individual metal sulphates, metal ion concentration, specific pH (ammoniacal solution), seeding and additives, thus restricting their applicability in complex situations as encountered in the processing of bleed stream. Moreover, because of the drawbacks such as the purification steps by precipitation, solvent extraction and ion exchange, separation of metals from a solution with multimetals, and incomplete recovery in hydrogen reduction, the existing processes are not recommended for the processing of copper bleed stream. The main object of the present invention is to prepare copper and nickel powders from the copper bleed stream, a waste by product generated in the processing of polymetallic sea nodules which obviates the drawbacks as detailed above. In the process of present invention, the copper bleed stream obtained from the electrowinning circuit of sea nodules treatment partially decopperised to equalise the level of copper and nickel and then evaporated to crystallisation of mixed sulphates of copper and nickel. From the mixed solution containing copper and nickel sulphates, iron is removed by precipitation. This solution is then processed for the metal powder preparation in autoclave by reducing with hydrogen gas. The preparation of copper powder is selectively carried out followed by subsequent nickel recovery as powder. The copper and nickel powders possess desired purity for Powder Metallurgical application. Accordingly the present invention provides an improved process for preparation of copper and nickel powder from copper bleed stream which comprises: (i) partially decopperising the sulphate phase said copper bleed stream containing polymetallic sulphate phase by electrolysis to reduce copper level equal to nickel at a current density of 150 to 300A/m2, (ii) separating the mixed copper and nickel sulphate phases from rest of the solution obtained in step (i) by known methods to obtain crystallise mixed sulphates of copper and nickel phases, (iii) leaching the said mixed copper and nickel sulphate phases in aqueous media followed by dilute sulphuric acid at a temperature of 30-100°C for a period of 1 to 8 hrs, (iv) reducing the resultant solution obtained in step (iii) by hydrogen gas to produce copper powder, (v) purifying the copper depleted solution obtained from step (iv), (vi) reducing the said purified copper depleted solution by hydrogen gas at a pressure range of 20-70 Kg/cm2to produce nickel powder at a temperature of 140- 250 ° C for 15-120 minutes with stirring rate varying from 20 to 80 stroke/min, (vii) washing and drying the said copper powder for powder metallurgical applications. In an embodiment of the present invention, the copper bleed solution employed may be selected from copper bleed stream obtained from polymetallic sea nodules processing in roast-ammonia leach- solvent extraction- electrowinning route may have the composition range Cu = 30-50 g/L Ni = 10-22g/l Co = 0.01-0.03 g/L Ee = 0.01-2.0 g/L Mn = 0.01-0.2 g/L Sb/As = 0.01-0.3 g/L H2S04= 100-250 g/L In still another embodiment of the present invention the electrolysis may be effected at a current density in the range of 150 to 300 A/m2 In still another embodiment of the present invention the partially decopperised solution may have the composition range: Cu= 15-45 g/L Ni=10-22g/l Co = 0.01-0.04 g/L Zn = 0.01-0.06 g/L Fe = 0.01-2.0 g/L Mn = 0.01-0.3 g/L Sb/As = 0.01-0.3 g/L H2S04= 120-260 g/L In yet -another embodiment of the present invention mixed copper and nickel sulphate phases may be obtained by evaporation and crystallisation of the partially decopperised solution at temperature range 80-110°C. The mixed sulphate may have 8-20% Cu, 8-21% Ni, 0.2-10% Fe and 1-6% H2SO4 after washing with water and drying at a temperature varying from 80-115°C. The mixed sulphate crystal may be dissolved in the aqueous solution at temperature range 30-100°C with solid/liquid ratio varying from 1:4 to 1:10 for a period of 1-8 h. The mother liquor with composition varying in the range 1.0-3.0 g/L Cu, 0.1-1.0 g/L Ni, 0.05-0.5 g/L Fe and 800-1500 g/L H2SO4 may be recycled to the electrolytic bath for acid make-up. In still another embodiment of the present invention, the leach liquor employed for preparation of copper powder by hydrogen reduction may be selected from the following composition range: Cu = 5-40 g/L Ni = 4-45 g/1 Fe = 0.01-2.0 g/L pH = 0.1-3.5 In still another embodiment of the present invention copper powder may be prepared from the leach liquor containing mixed copper and nickel sulphate crystal in the temperature range 100-180°C with hydrogen pressure range 10-45 kg/cm2 for a period of 10-120 minutes with stirring rate varying from 20 to 80 stroke/minute. The amount of seed copper powder required may be in the range 1-25 g/L. In still another embodiment of the present invention copper depleted solution may be purified for residual copper and other impurities by addition of sodium sulphide solution and pH adjustment. The purified solution may have composition range Ni = 3-32 g/1 Cu = 0.001-0.008 g/L pH = 3.5-10.5 In still another embodiment of the present invention, nickel powder may be prepared from the purified copper depleted solution in the temperature range 140-250°C with hydrogen pressure range 20-70 kg/cm2 for a 15-120 minutes with stirring rate varying from 20 to 80 stroke/minute. The amount of seed nickel powder required may be in the range 0.5-20 g/L. In the process of the present invention the prepared copper and nickel powders are washed with water followed by alcohol and dried in a stream of reducing gases such as hydrogen/ carbon monoxide to produce the powder for P/M applications. The metal powder prepared may be of 96.0-99.4% Cu and 96.0-99.8% nickel purity and with a recovery of 95.0-99.97% and 94.0-99.5% respectively. Novelty of the present invention is the use of copper bleed stream produced as waste material during the processing of polymetallic sea nodules by roast reduction-ammonia leach-solvent extraction and electrowinning route for production of copper and nickel powder. Another novel feature of the invention is selective production of copper and nickel powders under the controlled hydrogen pressure. The inventive step(s) of the present invention are partial decopperisation of the copper bleed stream by electrolysis, crystallisation of the partially decopperised solution to produce mixed copper nickel sulphate salt, dissolution of the mixed salt in dilute sulphuric acid, reduction of copper with hydrogen to produce copper powder, purification of copper depleted solution with sodium sulphide and finally reduction of nickel solution with hydrogen to produce nickel powder. The following examples are given by way of illustration and should not be construed to limit the scope of the invention. Example-1 Copper bleed solution containing 38 g/L Cu, 20.08 g/L Ni, 0.6 g/L Fe and 143.0 g/L H2SO4 was partially decopperised by electro winning at 100 A/m2 current density using 6% antimonial lead as insoluble anode and titanium sheet as cathode. A good quality of copper sheet of 99.93% purity was produced. The 2L of the said decopperised solution comprising 18.5 g/L Cu, 20.0 g/L Ni, 0.6 g/1 Fe and 153.4 g/L H2SO4 was evaporated at 100 °C and water washing to produced crystallised mixed sulphates of copper and nickel containing 11.0 % Cu, 12.2% Ni & 0.62 % Fe and hence reduce the volume giving 200 ml mother liquor with 3.0 g/L Cu, 0.4 g/L Ni, 0.3 g/L Fe and 1212 g/L H2SO4 for recycling. 50 g mixed sulphate crystal was leached in water and subsequently in dilute sulphuric acid at solid / liquid ratio of 1/5 at room temperature and produced leach liquor containing 17.6 g/L Cu, 18.838 g/L Ni & 0.6 g/L Fe. This leach liquor was added with NaOH to raise pH to 3.6 thereby precipitating iron. The said leach liquor was transferred to 2L capacity autoclave and reduced in hydrogen pressure of 20 kg/cm2 at 140 oC for 1 hour in presence of 10g copper seed at a constant stirring speed 50 stroke/minute. The precipitated copper powder was allowed to cool in the autoclave and then removed. The precipitated powder was filtered in a funnel and washed with water followed by washing with alcohol and drying with a flow of nitrogen at 110 oC to get P/M grade powder. Purity of the powder was 99% Cu with 0.57% Ni. The copper depleted solution was purified at 3.5 pH by the addition of sodium sulphide. The purified copper depleted solution containing 17.68 g/L Ni at 4.5 pH was transferred to an autoclave of 2L capacity and reduced in hydrogen pressure of 40 kg/cm2 at 190 oC for 90 minute in the presence of 10 g nickel seed at a constant stirring speed of 50 stroke/minute. After cooling the autoclave to room temperature, the solution with nickel powder filtered in a funnel. The powder was washed with water and alcohol and dried at 110 oC in a air oven to remove moisture. The powder was finally dried under a flow of hydrogen gas. The obtained nickel powder has a purity of 98.4% with 0.01% Cu and 0.425% Fe. Example-2 Copper bleed solution containing 35 g/L Cu, 22 g/L Ni, 0.58 g/L Fe and 152 g/L H2SO4 was partially decopperised. The 2L of the said decopperised solution comprising 19.37 g/L Cu, 22 g/L Ni, 0.59 g/L Fe and 174 g/L H2S04 was evaporated at 100 oC and water washing to produce crystallised mixed sulphates of copper and nickel containing 11.6% Cu, 11.7% Ni and 0.6% Fe. The mixed sulphate crystal was leached in water and subsequently in dilute sulphuric acid at solid / liquid ratio of 1/5 at room temperature and produced leach liquor containing 19.25 g/L Cu, 21.98 g/L Ni and 0.36 g/L Fe. This leach liquor was added with NaOH to raise the pH to 3.6 thereby precipitating iron. The purified leach liquor containing 19.2 g/L Cu, 21.9 g/L Ni and 0.01 g/L Fe was transferred to an autoclave and reduced in hydrogen pressure of 26 kg/cm2 at 140°C for 1 hour in the presence of 5 g copper seed at a constant stirring speed of 60 stroke/minute. Copper powder of 98.8% purity with 1.0% Ni was obtained on filtration of the precipitated powder followed by washing and drying at 110°C. The copper depleted solution was purified at 3.5 pH by the addition of sodium sulphide. The obtained purified copper depleted solution containing 21.0 g/L Ni at 4.5 pH was transferred to an autoclave and reduced in hydrogen pressure of 40 kg/cm2 at 180°C for 110 minutes in the presence of lOg nickel seed at a constant stirring speed of 40 stroke/minute. The obtained nickel powder has a purity of 98.45% with 1.3% Fe and trace Cu. Example-3 Copper bleed solution containing 38 g/L Cu, 20 g/L Ni, 0.6 g/L Fe and 143.0 g/L H2S04 was partially decopperised and evaporated at 100 oC to produce crystallised mixed sulphates of copper and nickel containing 11% Cu, 12.2% Ni and 0.62% Fe. The mixed sulphate crystal was leached in water and subsequently in dilute sulphuric acid at solid/liquid ratio of 1/4 at room temperature and produced leach liquor containing 25g/L Cu, 27g/L Ni,and 0.8g/L Fe. This leach liquor was added with NaOH to raise the pH to 3.6 thereby precipitating iron. The purified leach liquor containing 25g/L Cu, 26.98g/L Ni and 0.04g/L Fe was transferred to an autoclave and reduced in hydrogen pressure of 26 kg/cm2 at 130°C for 90 minute in the presence of 20g copper seed at constant stirring speed of 50 stroke/minute. The obtained copper powder was of 99.51% pure The copper depleted solution was purified at 3.5 pH by the addition of sodium sulphide. The obtained purified copper depleted solution containing 25 g/L Ni, 0.0008 g/L Cu and 0.006 g/L Fe was added with liquor ammonia (25%) to adjust the pH of the solution to 12.5. The solution was transferred to an autoclave and reduce in hydrogen pressure of 40 kg/cm2 at 190°C for 90 minute in the presence of 10 g nickel seed at a constant stirring speed of 50 stroke/minute. The obtained nickel powder is of 99.15% pure with 0.45 Fe and trace copper. The main advantages of the present invention are: 1. In the present invention partial decopperisation in the first step produces good quality (99.93%) copper cathode which is saleable. 2. In the present invention mother liquor containing sulphuric acid can be recycled to the refinery for acid make-up. 3. The mixed metal sulphate crystal can be easily solubilized and the metals can be prepared in the desired form such as metal salt, cathode and powder. 4. The preparation of copper and nickel powders by hydrogen reduction under different conditions has advantages over other processes where metal powders are prepared from the separated metals/solutions. 5. The process is ecofriendly and consumes less energy due to lesser number of processing steps. 6. In the present invention the purity of the copper and nickel powders obtained is suitable to meet the P/M applications. 7. The process is cost-effective as high value metal powders are produced as compared to other conventional processes. We claim: 1. An improved process for preparation of copper and nickel powder from copper bleed stream which comprises: (i) partially decopperising the sulphate phase said copper bleed stream containing polymetallic sulphate phase by electrolysis to reduce copper level equal to nickel, at a current density of 150 to 300 A/m2 (ii) separating the mixed copper and nickel sulphate phases from rest of the solution obtained in step (i) by known methods to obtain crystallise mixed sulphates of copper and nickel phases. (iii) leaching the said mixed copper and nickel sulphate phases in aqueous media followed by dilute sulphuric acid at a temperature of 30-100°C for a period of 1 to 8 hrs, (iv) reducing the resultant solution obtained in step (iii) by hydrogen gas to produce copper powder, (v) purifying the copper depleted solution obtained from step (iv), (vi) reducing the said purified copper depleted solution by hydrogen gas at a pressure range of 20-70 Kg/cm 2to produce nickel powder at a temperature of 140- 250 ° C for 15-120 minutes with stirring rate varying from 20 to 80 stroke /minute, (vii) washing and drying the said copper powder for powder metallurgical applications. 2. An improved process as claimed in claim 1 wherein the copper bleed stream employed is selected from copper bleed stream obtained from sea nodules processing in roast - ammonia leach - solvent extraction - electrowinning route having composition range: Cu = 30-50 g/L Ni = 10-22 g/1 Co = 0.01-0.03 g/L Zn = 0.01-0.05 g/L Fe = 0.01-2.0 g/L Mn = 0.01-0.2 g/L Sb/As = 0.01-0.3 g/L H2SO4 = 100-250 g/L 3. An improved process as claimed in claims 1-3 wherein the partially decopperised solution have composition range: Cu= 15-45 g/L Ni=10-22g/l Co= 0,.01-0.04 g/L Zn= 0.01-0.06 g/L Fe= 0.01-2.0 g/L Mn= 0.01-0.3 g/L Sb/As= 0.01-0.3 g/L H2SO4 = 120-260 g/L 4. An improved process as claimed in claims 1-3 wherein the mixed sulphate contains 8-20% Cu, 8-21% Ni, 0.2-10% Fe and 1-6% H2SO4 after washing with water beyond the above mentioned range. 5. An improved process as claimed in claims 1-4 wherein the mother liquor having composition in the range of 1.0-3.0 g/L Cu, 0.1-1 g/L Ni, 0.05-0.5 g/L Fe and 800 - 1500 g/L H2SO4 is recycled to the electrolytic bath for acid make up. 6. As improved process as claimed in claims 1-5 wherein the leach liquor employed for preparation of copper powder by hydrogen reduction is selected from the composition range: Cu= 5-40 g/L Ni = 4-45 g/L Fe = 0.0 1-2.0 g/L pH = 0.1-3.5 6. An improved process as claimed in claims 1-5 wherein copper powder prepared from the leach liquor containing mixed copper and nickel sulphate in the temperature range 100-180°C with hydrogen pressure range 10-45 kg/cm2 for a period 10-120 minutes with stirring rate varying from 20 to 80 stroke/min. The amount of seed copper powder required is in the range 1-25 g/L. 7. An improved process as claimed in claims 1-6 wherein copper depleted solution is purified for residual copper and other impurity by addition of sodium sulphide solution and pH adjustment. The purified solution have composition range: Ni = 3 - 32 g/L Cu = 0.001-0.008 g/L pH = 3.5-12.5 8. An improved process for the preparation of copper and nickel powders from copper bleed stream, substantially as herein described with reference to the examples.

Full Text

The present invention relates to an improved process for the preparation of copper and nickel powder from copper bleed stream.
The invention particularly relates to selectively producing copper and nickel powder by reducing copper level equal to nickel, separating mixed copper and nickel solution followed by hydrogen reduction of its mixed sulphate solution.
Copper bleed stream is produced in the processing of sea nodules by roast-ammonia leach - solvent extraction - electrowinning route, for controlling metallic impurities in the copper electrolysis. This solution consists of 16-20 g/L Ni and 35-45 g/L Cu besides 150-200 g/L H2SO4 and some other impurities which needs to be processed to recover valuable metals viz. nickel and copper. Producing nickel and copper powder from this solution will thus be the high value products which have specific demands and can be used in powder metallurgical (P/M) applications to make important components. Copper and nickel powders can also be prepared from the copper bleed stream of copper smelters. Besides, acidic and ammoniacal leach liquors of several lean grade and complex ores containing copper and nickel can be suitably processed to produce high value products.
As such no attempt appears to be made to process copper bleed stream produced in the processing of sea nodules. The known literature on the processing of sea nodules often shows the separation and recovery of copper, nickel and cobalt from the ammoniacal / sulphate / chloride leach solutions without mentioning the metal recovery (Cu and Ni) from the bleed solutions (Han, KN, Trans. HM, 51(1), 1998, p.55-67).
There are however, a number of literature reports on the processing of copper bleed streams of copper smelters. Reference may be made to Havlik et al (Havlik, T, Skrobian, M, Kammel, R, Curilla J and Cmorejova, D, Hydrometallurgy, 41, 1996, p.79-88) and Nagai et al (Nagai, T, Zaki, NY and Kobayashi, MMIJ, L-l, 1976, p. 1-4) wherein the copper bleed stream of copper smelter is subjected to a number of cumbersome steps such as (i) decopperisation to remove copper as poor quality nodular sheet (99.6% purity) for recharging to the smelter, (ii) evaporation / crystallisation of decopperised nickel sulphate solution to produce impure nickel sulphate and recycling the mother liquor to electrolysis section for acid make-up, (iii) purification of nickel sulphate by hydrometallurgical process, and (iv) crystallisation of nickel sulphate. The drawbacks are production of poor quality copper, recycling back of this copper to smelter thereby reducing the productivity, high-energy requirement, production of off-grade nickel sulphate crystal, environmental problems due to evolution of abnoxious arsine gasduring decopperisation etc. Reference may be made to Toyabe, K, Segawa, C and Sato H (In Proc. Electrorefining and winning of copper, 116 th Annual Meeting, Denver, Colorado, 1987, AIME Perm., p.99-116) and Shibata, T, Hashivchi, M and Kato, T, (116 th Annual Meeting, Dever, Colorado, 1987, AIME Perm., p.l 17-128) wherein the process is based on selective removal of Sb and Bi from electrolyte by adsorption on carbon or chelating resin and producing nickel sulphate crystals after removal of arsenic in deccopperisation step. In yet another process developed by Shibayama, R and Nagai, T (ISEC 1990, p. 1193-1198), chelating ion-exchange resin in combination with conventional process is used to recover copper and nickel cathodes/ sulphates. A process described by Abhishev, DN and Stryapkov, AV (ISEC'88, 1988, p.305-307) uses an alcohol for acid extraction and naphthenic acid to separate nickel and copper producing their sulphates. The drawbacks of the above processes are the involvement of very large number of processing steps and separation of individual components such as sulphuric acid, copper and nickel, besides producing metal salts or cathodes of lower return and payback. Reference may be made to Togashi, R and Nagai, T (Hydrometallurgy, 11, 1983, p. 149-163) wherein production of copper powder by hydrogen reduction from copper bleed stream with above 100 g/L sulphuric acid resulted in poor quality powder at higher depletion level. The drawbacks are removal of arsenic from the bleed stream, presence of bismuth ions for effective reduction of copper and need to purify electrolyte by solvent extraction.
There are known processes to produce copper and nickel powder by hydrogen reduction from the leach liquors of their respective ores. Reference may be made to US Patent 2,7976,342 (1957) wherein copper precipitation is followed with modification for other metals as well. Reference may be made to US Patent 332, 679 (1973) wherein attempts had been made to the continuous preparation of metal powders by hydrogen reduction from the leach solutions of metals from their ores. The main requirements of producing metal powders are purity of individual metal sulphates, metal ion concentration, specific pH (ammoniacal solution), seeding and additives, thus restricting their applicability in complex situations as encountered in the processing of bleed stream. Moreover, because of the drawbacks such as the purification steps by precipitation, solvent extraction and ion exchange, separation of metals from a solution with multimetals, and incomplete recovery in hydrogen reduction, the existing processes are not recommended for the processing of copper bleed stream.
The main object of the present invention is to prepare copper and nickel powders from the copper bleed stream, a waste by product generated in the processing of polymetallic sea nodules which obviates the drawbacks as detailed above.
In the process of present invention, the copper bleed stream obtained from the electrowinning circuit of sea nodules treatment partially decopperised to equalise the level of copper and nickel and then evaporated to crystallisation of mixed sulphates of copper and nickel. From the mixed solution containing copper and nickel sulphates, iron is removed by precipitation. This solution is then processed for the metal powder preparation in autoclave by reducing with hydrogen gas. The preparation of copper powder is selectively carried out followed by subsequent nickel recovery as powder. The copper and nickel powders possess desired purity for Powder Metallurgical application.
Accordingly the present invention provides an improved process for preparation of copper and nickel powder from copper bleed stream which comprises: (i) partially decopperising the sulphate phase said copper bleed stream containing
polymetallic sulphate phase by electrolysis to reduce copper level equal to
nickel at a current density of 150 to 300A/m2, (ii) separating the mixed copper and nickel sulphate phases from rest of the solution
obtained in step (i) by known methods to obtain crystallise mixed sulphates of
copper and nickel phases, (iii) leaching the said mixed copper and nickel sulphate phases in aqueous media
followed by dilute sulphuric acid at a temperature of 30-100°C for a period of 1
to 8 hrs, (iv) reducing the resultant solution obtained in step (iii) by hydrogen gas to produce
copper powder,
(v) purifying the copper depleted solution obtained from step (iv), (vi) reducing the said purified copper depleted solution by hydrogen gas at a pressure
range of 20-70 Kg/cm2to produce nickel powder at a temperature of 140- 250 ° C
for 15-120 minutes with stirring rate varying from 20 to 80 stroke/min, (vii) washing and drying the said copper powder for powder metallurgical
applications.
In an embodiment of the present invention, the copper bleed solution employed may be selected from copper bleed stream obtained from polymetallic sea nodules processing in roast-ammonia leach- solvent extraction- electrowinning route may have the composition range
Cu = 30-50 g/L
Ni = 10-22g/l
Co = 0.01-0.03 g/L
Ee = 0.01-2.0 g/L Mn = 0.01-0.2 g/L Sb/As = 0.01-0.3 g/L H2S04= 100-250 g/L
In still another embodiment of the present invention the electrolysis may be effected at a current density in the range of 150 to 300 A/m2
In still another embodiment of the present invention the partially decopperised solution may have the composition range: Cu= 15-45 g/L Ni=10-22g/l Co = 0.01-0.04 g/L Zn = 0.01-0.06 g/L Fe = 0.01-2.0 g/L Mn = 0.01-0.3 g/L Sb/As = 0.01-0.3 g/L H2S04= 120-260 g/L
In yet -another embodiment of the present invention mixed copper and nickel sulphate phases may be obtained by evaporation and crystallisation of the partially decopperised solution at temperature range 80-110°C. The mixed sulphate may have 8-20% Cu, 8-21% Ni, 0.2-10% Fe and 1-6% H2SO4 after washing with water and drying at a temperature varying from 80-115°C. The mixed sulphate crystal may be dissolved in the aqueous solution at temperature range 30-100°C with solid/liquid ratio varying from 1:4 to 1:10 for a period of 1-8 h.
The mother liquor with composition varying in the range 1.0-3.0 g/L Cu, 0.1-1.0 g/L Ni, 0.05-0.5 g/L Fe and 800-1500 g/L H2SO4 may be recycled to the electrolytic bath for acid make-up.
In still another embodiment of the present invention, the leach liquor employed for preparation of copper powder by hydrogen reduction may be selected from the following composition range: Cu = 5-40 g/L Ni = 4-45 g/1 Fe = 0.01-2.0 g/L pH = 0.1-3.5
In still another embodiment of the present invention copper powder may be prepared from the leach liquor containing mixed copper and nickel sulphate crystal in the temperature range 100-180°C with hydrogen pressure range 10-45 kg/cm2 for a period of 10-120 minutes with stirring rate varying from 20 to 80 stroke/minute. The amount of seed copper powder required may be in the range 1-25 g/L.
In still another embodiment of the present invention copper depleted solution may be purified for residual copper and other impurities by addition of sodium sulphide solution and pH adjustment. The purified solution may have composition range Ni = 3-32 g/1 Cu = 0.001-0.008 g/L pH = 3.5-10.5
In still another embodiment of the present invention, nickel powder may be prepared from the purified copper depleted solution in the temperature range 140-250°C with hydrogen pressure range 20-70 kg/cm2 for a 15-120 minutes with stirring rate varying from 20 to 80 stroke/minute. The amount of seed nickel powder required may be in the range 0.5-20 g/L.
In the process of the present invention the prepared copper and nickel powders are washed with water followed by alcohol and dried in a stream of reducing gases such as hydrogen/ carbon monoxide to produce the powder for P/M applications. The metal powder prepared may be of 96.0-99.4% Cu and 96.0-99.8% nickel purity and with a recovery of 95.0-99.97% and 94.0-99.5% respectively.
Novelty of the present invention is the use of copper bleed stream produced as waste material during the processing of polymetallic sea nodules by roast reduction-ammonia leach-solvent extraction and electrowinning route for production of copper and nickel powder. Another novel feature of the invention is selective production of copper and nickel powders under the controlled hydrogen pressure.
The inventive step(s) of the present invention are partial decopperisation of the copper bleed stream by electrolysis, crystallisation of the partially decopperised solution to produce mixed copper nickel sulphate salt, dissolution of the mixed salt in dilute sulphuric acid, reduction of copper with hydrogen to produce copper powder, purification of copper depleted solution with sodium sulphide and finally reduction of nickel solution with hydrogen to produce nickel powder.
The following examples are given by way of illustration and should not be construed to limit the scope of the invention.
Example-1
Copper bleed solution containing 38 g/L Cu, 20.08 g/L Ni, 0.6 g/L Fe and 143.0 g/L H2SO4 was partially decopperised by electro winning at 100 A/m2 current density using 6% antimonial lead as insoluble anode and titanium sheet as cathode. A good quality of copper sheet of 99.93% purity was produced. The 2L of the said decopperised solution comprising 18.5 g/L Cu, 20.0 g/L Ni, 0.6 g/1 Fe and 153.4 g/L H2SO4 was evaporated at 100 °C and water washing to produced crystallised mixed sulphates of copper and nickel containing 11.0 % Cu, 12.2% Ni & 0.62 % Fe and hence reduce the volume giving 200 ml mother liquor with 3.0 g/L Cu, 0.4 g/L Ni, 0.3 g/L Fe and 1212 g/L H2SO4 for recycling.
50 g mixed sulphate crystal was leached in water and subsequently in dilute sulphuric acid at solid / liquid ratio of 1/5 at room temperature and produced leach liquor containing 17.6 g/L Cu, 18.838 g/L Ni & 0.6 g/L Fe. This leach liquor was added with NaOH to raise pH to 3.6 thereby precipitating iron. The said leach liquor was transferred to 2L capacity autoclave and reduced in hydrogen pressure of 20 kg/cm2 at 140 oC for 1 hour in presence of 10g copper seed at a constant stirring speed 50 stroke/minute. The precipitated copper powder was allowed to cool in the autoclave and then removed. The precipitated powder was filtered in a funnel and washed with water followed by washing with alcohol and drying with a flow of nitrogen at 110 oC to get P/M grade powder. Purity of the powder was 99% Cu with 0.57% Ni.
The copper depleted solution was purified at 3.5 pH by the addition of sodium sulphide. The purified copper depleted solution containing 17.68 g/L Ni at 4.5 pH was transferred to an autoclave of 2L capacity and reduced in hydrogen pressure of 40 kg/cm2 at 190 oC for 90 minute in the presence of 10 g nickel seed at a constant stirring speed of 50 stroke/minute. After cooling the autoclave to room temperature, the solution with nickel powder filtered in a funnel. The powder was washed with water and alcohol and dried at 110 oC in a air oven to remove moisture. The powder was finally dried under a flow of hydrogen gas. The obtained nickel powder has a purity of 98.4% with 0.01% Cu and 0.425% Fe.
Example-2
Copper bleed solution containing 35 g/L Cu, 22 g/L Ni, 0.58 g/L Fe and 152 g/L H2SO4 was partially decopperised. The 2L of the said decopperised solution comprising 19.37 g/L Cu, 22 g/L Ni, 0.59 g/L Fe and 174 g/L H2S04 was evaporated at 100 oC and water washing to produce crystallised mixed sulphates of copper and nickel containing 11.6% Cu, 11.7% Ni and 0.6% Fe.
The mixed sulphate crystal was leached in water and subsequently in dilute sulphuric acid at solid / liquid ratio of 1/5 at room temperature and produced leach liquor containing 19.25 g/L Cu, 21.98 g/L Ni and 0.36 g/L Fe. This leach liquor was added with NaOH to raise the pH to 3.6
thereby precipitating iron. The purified leach liquor containing 19.2 g/L Cu, 21.9 g/L Ni and 0.01 g/L Fe was transferred to an autoclave and reduced in hydrogen pressure of 26 kg/cm2 at 140°C for 1 hour in the presence of 5 g copper seed at a constant stirring speed of 60 stroke/minute. Copper powder of 98.8% purity with 1.0% Ni was obtained on filtration of the precipitated powder followed by washing and drying at 110°C.
The copper depleted solution was purified at 3.5 pH by the addition of sodium sulphide. The obtained purified copper depleted solution containing 21.0 g/L Ni at 4.5 pH was transferred to an autoclave and reduced in hydrogen pressure of 40 kg/cm2 at 180°C for 110 minutes in the presence of lOg nickel seed at a constant stirring speed of 40 stroke/minute. The obtained nickel powder has a purity of 98.45% with 1.3% Fe and trace Cu.
Example-3
Copper bleed solution containing 38 g/L Cu, 20 g/L Ni, 0.6 g/L Fe and 143.0 g/L H2S04 was partially decopperised and evaporated at 100 oC to produce crystallised mixed sulphates of copper and nickel containing 11% Cu, 12.2% Ni and 0.62% Fe.
The mixed sulphate crystal was leached in water and subsequently in dilute sulphuric acid at solid/liquid ratio of 1/4 at room temperature and produced leach liquor containing 25g/L Cu, 27g/L Ni,and 0.8g/L Fe. This leach liquor was added with NaOH to raise the pH to 3.6 thereby precipitating iron. The purified leach liquor containing 25g/L Cu, 26.98g/L Ni and 0.04g/L Fe was transferred to an autoclave and reduced in hydrogen pressure of 26 kg/cm2 at 130°C for 90 minute in the presence of 20g copper seed at constant stirring speed of 50 stroke/minute. The obtained copper powder was of 99.51% pure
The copper depleted solution was purified at 3.5 pH by the addition of sodium sulphide. The obtained purified copper depleted solution containing 25 g/L Ni, 0.0008 g/L Cu and 0.006 g/L Fe was added with liquor ammonia (25%) to adjust the pH of the solution to 12.5. The solution was transferred to an autoclave and reduce in hydrogen pressure of 40 kg/cm2 at 190°C for 90 minute in the presence of 10 g nickel seed at a constant stirring speed of 50 stroke/minute. The obtained nickel powder is of 99.15% pure with 0.45 Fe and trace copper.
The main advantages of the present invention are:
1. In the present invention partial decopperisation in the first step produces good quality
(99.93%) copper cathode which is saleable.
2. In the present invention mother liquor containing sulphuric acid can be recycled to the
refinery for acid make-up.
3. The mixed metal sulphate crystal can be easily solubilized and the metals can be prepared in the desired form such as metal salt, cathode and powder.
4. The preparation of copper and nickel powders by hydrogen reduction under different
conditions has advantages over other processes where metal powders are prepared from the
separated metals/solutions.
5. The process is ecofriendly and consumes less energy due to lesser number of processing steps.
6. In the present invention the purity of the copper and nickel powders obtained is suitable to
meet the P/M applications.
7. The process is cost-effective as high value metal powders are produced as compared to other
conventional processes.

We claim:
1. An improved process for preparation of copper and nickel powder from copper bleed stream which comprises:
(i) partially decopperising the sulphate phase said copper bleed stream containing polymetallic sulphate phase by electrolysis to reduce copper level equal to nickel, at a current density of 150 to 300 A/m2
(ii) separating the mixed copper and nickel sulphate phases from rest of the solution obtained in step (i) by known methods to obtain crystallise mixed sulphates of copper and nickel phases.
(iii) leaching the said mixed copper and nickel sulphate phases in aqueous media followed by dilute sulphuric acid at a temperature of 30-100°C for a period of 1 to 8 hrs, (iv) reducing the resultant solution obtained in step (iii) by hydrogen gas to produce copper powder,
(v) purifying the copper depleted solution obtained from step (iv), (vi) reducing the said purified copper depleted solution by hydrogen gas at a pressure range of 20-70 Kg/cm 2to produce nickel powder at a temperature of 140- 250 ° C for 15-120 minutes with stirring rate varying from 20 to 80 stroke /minute, (vii) washing and drying the said copper powder for powder metallurgical applications. 2. An improved process as claimed in claim 1 wherein the copper bleed stream employed is selected from copper bleed stream obtained from sea nodules processing in roast - ammonia leach - solvent extraction - electrowinning route having composition range:
Cu = 30-50 g/L
Ni = 10-22 g/1
Co = 0.01-0.03 g/L
Zn = 0.01-0.05 g/L
Fe = 0.01-2.0 g/L
Mn = 0.01-0.2 g/L
Sb/As = 0.01-0.3 g/L
H2SO4 = 100-250 g/L
3. An improved process as claimed in claims 1-3 wherein the partially decopperised solution have composition range: Cu= 15-45 g/L

Ni=10-22g/l Co= 0,.01-0.04 g/L Zn= 0.01-0.06 g/L Fe= 0.01-2.0 g/L Mn= 0.01-0.3 g/L Sb/As= 0.01-0.3 g/L H2SO4 = 120-260 g/L
4. An improved process as claimed in claims 1-3 wherein the mixed sulphate
contains 8-20% Cu, 8-21% Ni, 0.2-10% Fe and 1-6% H2SO4 after washing with
water beyond the above mentioned range.
5. An improved process as claimed in claims 1-4 wherein the mother liquor having
composition in the range of 1.0-3.0 g/L Cu, 0.1-1 g/L Ni, 0.05-0.5 g/L Fe and 800 - 1500
g/L H2SO4 is recycled to the electrolytic bath for acid make up.
6. As improved process as claimed in claims 1-5 wherein the leach liquor employed
for preparation of copper powder by hydrogen reduction is selected from the
composition range:
Cu= 5-40 g/L Ni = 4-45 g/L Fe = 0.0 1-2.0 g/L pH = 0.1-3.5
6. An improved process as claimed in claims 1-5 wherein copper powder prepared
from the leach liquor containing mixed copper and nickel sulphate in the temperature
range 100-180°C with hydrogen pressure range 10-45 kg/cm2 for a period 10-120
minutes with stirring rate varying from 20 to 80 stroke/min. The amount of seed copper
powder required is in the range 1-25 g/L.
7. An improved process as claimed in claims 1-6 wherein copper depleted solution
is purified for residual copper and other impurity by addition of sodium sulphide solution
and pH adjustment. The purified solution have composition range:
Ni = 3 - 32 g/L
Cu = 0.001-0.008 g/L
pH = 3.5-12.5
8. An improved process for the preparation of copper and nickel powders from copper bleed stream, substantially as herein described with reference to the examples.

Documents:

700-del-2000-abstract.pdf

700-del-2000-claims.pdf

700-del-2000-correspondence-others.pdf

700-del-2000-correspondence-po.pdf

700-del-2000-description (complete).pdf

700-del-2000-form-1.pdf

700-del-2000-form-19.pdf

700-del-2000-form-2.pdf

« Previous Patent

Next Patent »

Patent Number

232793

Indian Patent Application Number

700/DEL/2000

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

21-Mar-2009

Date of Filing

31-Jul-2000

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESARCH

Applicant Address

RAFI MARG, NEW DELHI- 110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	BANSHI DHAR PANDEY	NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR, BIHAR, INDIA.
2	DULAL BAGCHI	NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR, BIHAR, INDIA.
3	VINAY KUMAR	NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR, BIHAR, INDIA.
4	PREMCHAND	NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR, BIHAR, INDIA.

PCT International Classification Number

B22F9/24

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA