Title of Invention	"AN IMPROVED PROCESS FOR THE PREPARATION OF COPPER AND NICKEL POWDER FROM WASTE SOLUTION OR STREAM CONTAINING COPPER AND NICKEL"
Abstract	An improved process for the preparation of copper and nickel powder from waste solution or stream containing copper and nickel (i) selecting the waste solution or stream containing copper and nickel and partially de-copperising the said copper bleed stream by electrolysis to bring down the copper level equal to nickel (ii )evaporating the said solution to crystallise out mixed sulphate salts of copper and nickel, (iii Reaching the mixed copper and nickel sulphate salts in aqueous medium at room temperature by maintaining the solid/liquid ratio in the range between ¼ to 1/10 for a period of 1-8 h, (iv ) removing the impurities like iron from the mixed sulphate solution obtained in step (iii) by maintaining the pH in the range between 3-5 and precipitating thereof by the known method. (v ) separating copper and nickel from the purified mixed sulphate solution from step(iv) by solvent extraction using an organic substance having oxime / salicyldoxime as an active group diluted in kerosene, thus copper getting loaded in the organic phase leaving nickel in the raffinate. (vi) stripping loaded copper from the organic phase by sulphuric acid solution. (vii ) electrolysis of the copper sulphate solution produced in step(vi) and nickel sulphate left un-extracted in the raffinate during solvent extraction. (viii ) washing and drying of the copper and nickel powder for powder metallurgical [P/M] applications.

Title of Invention

"AN IMPROVED PROCESS FOR THE PREPARATION OF COPPER AND NICKEL POWDER FROM WASTE SOLUTION OR STREAM CONTAINING COPPER AND NICKEL"

Abstract

An improved process for the preparation of copper and nickel powder from waste solution or stream containing copper and nickel (i) selecting the waste solution or stream containing copper and nickel and partially de-copperising the said copper bleed stream by electrolysis to bring down the copper level equal to nickel (ii )evaporating the said solution to crystallise out mixed sulphate salts of copper and nickel, (iii Reaching the mixed copper and nickel sulphate salts in aqueous medium at room temperature by maintaining the solid/liquid ratio in the range between ¼ to 1/10 for a period of 1-8 h, (iv ) removing the impurities like iron from the mixed sulphate solution obtained in step (iii) by maintaining the pH in the range between 3-5 and precipitating thereof by the known method. (v ) separating copper and nickel from the purified mixed sulphate solution from step(iv) by solvent extraction using an organic substance having oxime / salicyldoxime as an active group diluted in kerosene, thus copper getting loaded in the organic phase leaving nickel in the raffinate. (vi) stripping loaded copper from the organic phase by sulphuric acid solution. (vii ) electrolysis of the copper sulphate solution produced in step(vi) and nickel sulphate left un-extracted in the raffinate during solvent extraction. (viii ) washing and drying of the copper and nickel powder for powder metallurgical [P/M] applications.

Full Text	The present invention relates to an improved process for the preparation of copper and nickel powder from waste solution or stream containing copper and nickel. The invention particularly relates to selectively producing copper and nickel powder by the treatment of copper bleed electrolyte generated in the electro-refining of impure metal of copper smelters through partial de-copperisation to bring copper level equal to nickel, crystallisation of the copper and nickel containing solution, leaching with water followed by iron removal, separating and recovering copper and nickel fi-om the mixed solution by solvent extraction, electrolysing the copper nickel sulphate solutions to get pure metal powder. Copper bleed electrolyte is generated during the electro-refining of the impure copper in the copper-producing units and has substantial amount of nickel besides a host of other impurities. Copper and nickel are the metals of strategic importance and therefore this invention will be useful for producing value added products such as powders with specific demand in the areas like powder metallurgical (P/M) applications BACKGROUND OF THE INVENTION The existing practice for the bleed electrolyte purification is removal of copper, arsenic and antimony by electrolytic stripping in the liberator cell, followed by liquor concentration to crystallise out salt of nickel and recycling of the black acid to the system. But the associated drawbacks are liberation of the arsine gas, high operation cost, poor grade NiSO4, and loss of acid (Habashi, F., Ismail, M.I., Health hazards and pollution in the metallurgical industry due to phosphine and arsine, CIM Bull, 68(760), 99-103, 1975.). Processing of copper bleed streams of copper smelters have been reported in literature. 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-1, 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 gas during de-copperisation 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 Penn., p.99-116) and Shibata, T, Hashivchi, M and Kato, T,l 16 th Annual Meeting, Dever, Colorado, 1987, AIME Penn., p. 117-128) 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 de-copperisation step. In yet another process developed by Shibayama, R and Nagai, T (ISEC 1990, p.l 193-1198), chelating ion-exchange resin in combination with conventional process is used to recover copper and nickel cathodes/ sulphates/powders. A process is reported by 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 result 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. There are other knovm 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. Reference may also 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, seeding and additives, thus restricting their applicability in complex situations as encountered in the processing of copper bleed solutions. Moreover, because of the drawbacks such as the purification steps by precipitation, separation of metals from a solution with multi metals, and incomplete recovery in hydrogen reduction, the existing processes are not considered for the processing of the copper bleed electrolytes. The main object of the present invention is to provide an improved process for the preparation of copper and nickel powder from the waste solution and stream containing copper and nickel. In an object of the present invention the partial decopperisation in the first step produces good quality (99.93%) copper cathode which is salable. In an object of the present invention the mother liquor obtained in the crystallisation step containing sulphuric acid can be recycled to the refinery for acid make-up. In another object of the present invention the mixed metal sulphate crystal can be dissolved easily and the metals can be recovered with the help of solvent extraction in the desired form such as metal salt, cathode and electrolytic grade powder. In yet another object of the present invention the preparation of copper and nickel powders by solvent extraction-electrolysis route has advantages such as clear separation of the two metals with high recovery. In yet another object of the present invention the process is ecofi"iendly and the spent solutions obtained fi-om the electrolysis step can by recycled back to the system. In yet another object of the present invention the purity of the copper and nickel powders produced is suitable to meet the P/M applications. Novelty of the present invention is recovery and preparation of value added products viz electrolytic grade copper and nickel powder fi-om copper bleed electrolyte generated during the electro-refining of the impure copper produced in a copper plant. The main novelty of the invention is production of high purity P/M grade metal powders by partial decopperisation-crystallisation-solvent extraction-electrolysis which is no where cited in the literature. In the process of present invention, the impurity laden copper bleed electrolyte generated from the electrolytic tank, which is periodically discarded from the system is partially decopperised to bring down copper level equal to the level of nickel and then evaporated to crystallise mixed sulphates of copper and nickel. From the mixed solution containing copper and nickel sulphates, pH was adjusted and iron was removed by precipitation. This solution is then subjected to solvent extraction to separate copper and nickel, copper was stripped from the loaded organic as copper sulphate, and electrolysis of the copper sulphate from stripping operation and the nickel sulphate left un-extracted in the raffinate, to get pure copper and nickel powders. The copper and nickel powders thus produced possess desired purity for Powder Metallurgical (P/M) application. Accordingly, the present invention provides an improved process for the preparation of copper and nickel powder from waste solution or stream containing copper and nickel which comprises: (i) selecting the waste solution or stream containing copper and nickel and partially de-copperising the said copper bleed stream by electrolysis to bring down the copper level equal to nickel (ii) evaporating the said solution to crystallise out mixed sulphate salts of copper and nickel. (iii) leaching the mixed copper and nickel sulphate salts in aqueous medium at room temperature by maintaining the solid/liquid ratio in the range between 1/4 to 1/10 for a period of l-8h, (iv) removing the impurities like iron from the mixed sulphate solution obtained in step (iii) by maintaining the pH in the range between 3-5 and precipitating thereof by the known method. (v) separating copper and nickel from the purified mixed sulphate solution from step(iv) by solvent extraction using an organic substance having oxime / salicyldoxime as an active group diluted in kerosene, thus copper getting loaded in the organic phase leaving nickel in the raffinate. (vi) stripping loaded copper from the organic phase by sulphuric acid solution. (vii) electrolysis of the copper sulphate solution produced in step(vi) and nickel sulphate left un-extracted in the raffinate during solvent extraction to get pure copper and nickel powders. (viii) washing and drying of the copper and nickel powder for P/M applications. In an embodiment of the present invention, the waste solution or stream containing copper and nickel used may be selected fi-om the copper bleed electrolyte generated during the electro-refining of impure metal in the electrolytic tank in a copper producing industry having the composition range: Cu = 30-60 g/L Ni = 7-22 g/1 Bi = 0.0-0.3 g/L Fe = 0.1-2.0 g/L H2SO4 = 150-200 g/L In another embodiment of the present invention the partially decopperised solution may have the composition range: Cu = 12-25 g/L Ni = 7-25 g/1 Bi = 0.0-0.3g/L Fe = 0.1-2.0 g/L H2SO4 = 160 -300 g/L In still 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 80-100°C for different evaporation percentage ranging from 33-85%. In yet another embodiment the mixed sulphate may have 8-15% Cu, 10-16% Ni, 0.1-1.0% Fe, 0.0 -0.06% Bi and 5-20g/L H2SO4 after washing with water and drying at a temperature varying from 70-100'C. In still another embodiment of the present invention, the leach liquor employed for preparation of copper and nickel powder after iron removal by solvent extraction may be selected from the following composition range: Cu = 5-15 g/L Ni = 8-20 g/1 Fe = 0.0001-0.0004 g/L Bi = 0-0.06g/L pH = 0.1-3.0 In still another embodiment of the present invention copper and nickel powder may be prepared from the leach liquor containing mixed copper and nickel sulphate after their separation using 5-30% of an organic substance with oxime/salicyldoxime as the active group, diluted in kerosene. The organic/aqueous(0/A) is varied in the range 4/1 to 1/1 for a stirring period of 2-15 minutes on the bench scale(shake-out experiments). In yet another embodiment of the present invention the metal powder is prepared from the separated copper and nickel sulphate of leach liquor in a continuous mode using a mixer- settler unit. A 5-30% organic reagent mentioned above in kerosene can be used to extract copper in 2-6 stages with 1-4 stages of scrubbing and 1-5 stages stripping with the spent electrolyte as stripping solution. In yet another embodiment of the present invention the electrolytic grade copper powder is prepared from the strip solution from the solvent extraction step with the composition in the range 30-70g/L Cu, 0-0.99g/L Ni and 100-200g/LH2SO4, at the current density in the range 500-lOOOA/m^ in the electrolysis. Nickel powder is prepared by electrolysis of the raffinate solution with the composition range: 8-20g/L Ni, 0-0.4g/L Cu along with 10-60 g/L (NH4)2SO4, 0-15g/L H3BO3 and 0.01-0.5g/L thiourea in the pH range 3.5-9.0 while imparting current density in the range 3000-10,000 A/ml In yet another embodiment of the present invention the copper and nickel powders prepared by the electrolysis of their respective sulphates is washed with water. Copper powder is then washed with a solution of a reducing agent to restrict oxidation of the copper powder and dried at lOO^C to produce pure powder for P/M applications. The metal powders prepared may be of 99.93% copper and 99.8% nickel with a current efficiency varying in the range of 85.0-99% for copper and 45-65% for nickel respectively. 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 38.4g/L Cu, 19.4 g/L Ni, 0.76 g/L Fe, 0.2g/L Bi and 171.0 g/L H2SO4 was partially decopperised by electrowinning at a current density 100 A/m using 6% antimonial lead as insoluble anode and titanium sheet as cathode. A good quality of copper sheet of 99.5% purity was produced. The 950ml of the said decopperised solution comprising 17.9 g/L Cu, 20.4 g/L Ni, 0.76 g/1 Fe and 207 g/L H2SO4 was evaporated to produce mixed sulphate crystals of copper and nickel containing 8.39% Cu, 13.67% Ni and 0.50% Fe, 0.01%Bi and 20g/L H2SO4 with the volume of the mother liquor left to 210ml with 8.57g/L Cu, 6.72 g/L Ni, 0.25g/L Fe and 187g/L H2SO4 for recycling. Mixed sulphate crystal was leached with water at solid / liquid ratio of 1/5 at room temperature producing leach liquor containing 8.39g/L Cu, 13.67g/L Ni & 0.6 g/L Fe. NaOH was then added to this leach liquor to raise pH to 3.6 followed by aeration to precipitate iron thereby giving clarified solution containing 8.4g/L Cu, 13.7g/LNi, 0.005g/L Fe. The said leach liquor was then used for solvent extraction using 25% LIX 84 in kerosene to separate copper from nickel at 0/A:l/l with a contact time of 5min in batch mode. Copper loaded organic was scrubbed by scrubbing solution with 1 .Og/L H2SO4 to remove entrapped nickel and finally stripped with 180g/L sulphuric acid solution to bring copper as sulphate into the aqueous solution. This copper sulphate solution containing 37.8g/L Cu, 0.08g/L Ni, trace Fe and 166g/L H2SO4 was then electrolysed at a current density of 600A/m^ to make copper powder. The raffinate containing nickel was adjusted to get lOg/L Ni, 0.006g/L Cu, 40g/L (NH4)2SO4 , 10 g/L H3BO3 and 0.2g/L thiourea, which on electrolysis at a current density of 4000A/m^ produced nickel powder. The copper and nickel powders so formed were washed with water followed by treatment with a reducing agent to prevent the oxidation and dried at 100°C to get P/M grade powder of 99.9%Cu and 99.8%Ni. Example-2 Copper bleed solution was subjected to partial decopperisation-crystallisation of mixed sulphate of copper and nickel-leaching and iron precipitation to get the iron free solution as mentioned in example 1. This leach liquor was then used for solvent extraction using 25% LIX 84 to separate copper from nickel in a mixer settler unit under continuous mode. About 99.8% copper was extracted in 4 stages leaving O.OOlg/L of Cu, 11.37%Ni in the raffinate. Loaded organic was scrubbed with dilute sulphuric acid (1.73g/L) to remove entrapped nickel in 2 stages and finally sfripped with stripping solution containing 30.25g/L Cu, 0.203g/L Ni and 179.34g/L H2SO4 in 2 stages to get copper sulphate solution. This solution containing 37.8g/L Cu, 0.6g/LNi and 166g/L H2SO4 was electrolysed at a current density of 800A/m^ to make copper powder. To the raffinate containing 11.37g/L Ni and traces of copper, 40g/L (NH4)2SO4, llg/L H3BO3 and 0.2g/L thiourea at pH 4.5 were added and was electrolysed at a current density of 6000A/m to get nickel powder. The copper/nickel powder was washed with water followed by treatment with a reducing agent to prevent the oxidation of powder and dried at 100°C to get P/M grade powders of 99.93% Cu and 99.81% Ni.. Example-3 Copper bleed solution containing 39.9g/L Cu, 9.6g/L Ni, 0.69 g/L Fe and 194.04g/L H2SO4 was partially decopperised. A 990ml of the said decopperised solution comprising 17.75 g/L Cu, 9.4g/L Ni, 0.76g/L Fe and 200g/L H2SO4 was evaporated at 100°C to produce crystals of mixed sulphates of copper and nickel which on water washing had 11.06 % Cu, 12.46% Ni and 0.54% Fe, 0.045%Bi and 13.3%H2SO4. The mixed sulphate crystal was leached in water at solid / liquid ratio of 1/5 at room temperature to produce leach liquor containing 11.0 g/L Cu, 12.5 g/L Ni and 0.5 g/L Fe. NaOH was added to this leach liquor to raise the pH to above 4.0 and was aerated thereby precipitating iron. The purified leach liquor containing 19.25 g/L Cu, 21.98 g/L Ni and 0.0004 g/L Fe was used for the solvent extraction of copper and nickel using 20% LIX84 in kerosene as an extractant. Bench scale simulation of copper and nickel extraction was done and about 99.8% of copper was extracted in 4 stages at an 0/A: 1.5/1 in a contact time of three min. leaving nickel in the raffinate solution. The scrubbing and stripping of the organic with Ig/L and 170g/L H2SO4 produced scrub and strip solution respectively. On electrolysis of copper sulphate from the strip solution containing 38g/L Cu, 0.1 g/L Ni, trace Fe and 160g/L H2SO4 at a current density of lOOOA/m^ copper powder was obtained. The raffinate containing 12g/L Ni. 0.004g/LCu was adjusted by making addition to get the solution with 45g/L (NH4)2SO4, 9g/L H3BO3 and 0.15g/L thiourea; which on electrolysis at a current density of 8000A/m^ produced nickel powder. The copper and nickel powders were washed and dried as mentioned in example 1. The purity of the metal powder was 99.93% Cu and 99.82% Ni. Advantages The main advantages of the present invention are: 1. The partial decopperisation in the first step produces good quality (99.93%) copper cathode which is salable. 2. The mother liquor obtained in the crystallisation step containing sulphuric acid can be recycled to the refinery for acid make-up. 3. The mixed metal sulphate crystal can be dissolved easily and the metals can be recovered with the help of solvent extraction in the desired form such as metal salt, cathode and electrolytic grade powder. 4. The preparation of copper and nickel powders by solvent extraction-electrolysis route has advantages such as clear separation of the two metals with high recovery. 5. The process is ecofriendly and the spent solutions obtained from the electrolysis step can by recycled back to the system. 6. In the present invention the purity of the copper and nickel powders produced 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 the preparation of copper and nickel powder from waste solution or stream containing copper and nickel (i) selecting the waste solution or stream containing copper and nickel and partially de-copperising the said copper bleed stream by electrolysis to bring down the copper level equal to nickel (ii) evaporating the said solution to crystallise out mixed sulphate salts of copper and nickel, (iii) leaching the mixed copper and nickel sulphate salts in aqueous medium at room temperature by maintaining the solid/liquid ratio in the range between ¼ to 1/10 for a period of 1-8 h, (iv) removing the impurities like iron from the mixed sulphate solution obtained in step (iii) by maintaining the pH in the range between 3-5 and precipitating thereof by the known method. (v) separating copper and nickel from the purified mixed sulphate solution from step(iv) by solvent extraction using an organic substance having oxime / salicyldoxime as an active group diluted in kerosene, thus copper getting loaded in the organic phase leaving nickel in the raffinate. (vi) stripping loaded copper from the organic phase by sulphuric acid solution, (vii) electrolysis of the copper sulphate solution produced in step(vi) and nickel sulphate left un-extracted in the raffinate during solvent extraction, (viii) washing and drying of the copper and nickel powder for powder metallurgical [P/M] applications. 2. An improved process as claimed in claim 1 wherein the copper waste solution/stream employed is selected from the copper bleed stream generated during the electro-refining of impure metal in the electrolytic tank in a copper producing industry having the composition range: Cu = 30-60 g/L Ni = 7-22 g/L Bi = 0.0-0.3 g/L Fe = 0.1-2.0 g/L H2SO4 = 150-200 g/L 3. An improved process as claimed in claims 1-2 wherein the partially decopperised solution have composition range: Cu= 12-25 g/L Ni = 7-25 g/1 Bi = 0.0-0.3g/L Fe = 0.1- 2.0 g/L H2SO4= 160-300 g/L 4. An improved process as claimed in claims 1-3 wherein mixed copper and nickel sulphate phases obtained by evaporation and crystallisation of the partially decopperised solution at temperature range 80 to 100°C, the mixed sulphate at different evaporation percentage ranging from 33-65% may have 8-15g/L Cu, 10-16g/L Ni, 0.1-1.0g/L Fe, 0.0-0.06%Bi and 5-20% H2SO4 after washing with water and drying at 80-100°C. 5. As improved process as claimed in claims 1-4 wherein the leach liquor employed for preparation of metal powder after iron removal, and separating copper and nickel by solvent extraction is selected from the following composition range: Cu = 5-15 g/L Ni= 8-20 g/1 Fe = 0.0001-0.0004 g/L Bi=0.0-0.06g/L pH = 0.1-3.0 6. An improved process as claimed in claims 1-5 wherein metal powder is prepared from the separated copper and nickel from the leach liquor using 5-30% LIX 84 in kerosene at organic/aqueous [O/A] ratio 4/1 to 1/1 for a stirring period of 2-15 minutes on the bench scale (shakeout experiments). 7. An improved process as claimed in claims 1-6 wherein metal powder is prepared from the separated copper and nickel sulphate of the leach liquor in a continuous mode using a mixer- settler unit. 8. An improved process as claimed in claims 1-7 wherein copper powder is prepared by electrolysis at the current density in the range 500-1000A/m2 of the strip solution in the composition range : 30-70 g/L Cu, 0.0-0.99gL Ni, 100-200g/L H2SO4 and nickel powder is produced at a current density of 4000-10,000A/m2 with the raffinate solution having the composition in the range: 8-20 g/L Ni, 0.0-0.04 g/L Cu, 10-60 g/L (NH4)2SO4, 0-15 g/L H3BO3 and 0.01-0.5g/L thiourea. 9. An improved process as claimed in claims 1-8 wherein copper and nickel powders prepared by the electrolysis of their respective sulphate solutions are washed with water followed by treatment with a reducing agent to restrict oxidation and dried at 100°C to produce powders for powder metallurgical [P/M] applications, the metal powders prepared is of 99.9% Cu and 99.8% nickel with a current efficiency varying in the range of 85.0- 99% for copper and 45-65% for nickel respectively. 10. An improved process for the preparation of copper and nickel powder from waste solution or stream containing copper and nickel is substantially 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 waste solution or stream containing copper and nickel. The invention particularly relates to selectively producing copper and nickel powder by the treatment of copper bleed electrolyte generated in the electro-refining of impure metal of copper smelters through partial de-copperisation to bring copper level equal to nickel, crystallisation of the copper and nickel containing solution, leaching with water followed by iron removal, separating and recovering copper and nickel fi-om the mixed solution by solvent extraction, electrolysing the copper nickel sulphate solutions to get pure metal powder. Copper bleed electrolyte is generated during the electro-refining of the impure copper in the copper-producing units and has substantial amount of nickel besides a host of other impurities. Copper and nickel are the metals of strategic importance and therefore this invention will be useful for producing value added products such as powders with specific demand in the areas like powder metallurgical (P/M) applications
BACKGROUND OF THE INVENTION
The existing practice for the bleed electrolyte purification is removal of copper, arsenic and antimony by electrolytic stripping in the liberator cell, followed by liquor concentration to crystallise out salt of nickel and recycling of the black acid to the system. But the associated drawbacks are liberation of the arsine gas, high operation cost, poor grade NiSO4, and loss of acid (Habashi, F., Ismail, M.I., Health hazards and pollution in the metallurgical industry due to phosphine and arsine, CIM Bull, 68(760), 99-103, 1975.).
Processing of copper bleed streams of copper smelters have been reported in literature. 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-1, 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 gas during de-copperisation 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 Penn., p.99-116) and Shibata, T, Hashivchi, M and Kato, T,l 16 th Annual Meeting, Dever, Colorado, 1987, AIME Penn., p. 117-128) 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 de-copperisation step. In yet another process developed by Shibayama, R and Nagai, T (ISEC 1990, p.l 193-1198), chelating ion-exchange resin in combination with conventional process is used to recover copper and nickel cathodes/ sulphates/powders. A process is reported by 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 result 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.
There are other knovm 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. Reference may also 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, seeding and additives, thus restricting their applicability in complex situations as encountered in the processing of copper bleed solutions. Moreover, because of the drawbacks such as the purification steps by precipitation, separation of metals from a solution with multi metals, and incomplete recovery in hydrogen reduction, the existing processes are not considered for the processing of the copper bleed electrolytes.
The main object of the present invention is to provide an improved process for the preparation of copper and nickel powder from the waste solution and stream containing copper and nickel.
In an object of the present invention the partial decopperisation in the first step produces good quality (99.93%) copper cathode which is salable. In an object of the present invention the mother liquor obtained in the crystallisation step containing sulphuric acid can be recycled to the refinery for acid make-up.
In another object of the present invention the mixed metal sulphate crystal can be dissolved easily and the metals can be recovered with the help of solvent extraction in the desired form such as metal salt, cathode and electrolytic grade powder.
In yet another object of the present invention the preparation of copper and nickel powders by solvent extraction-electrolysis route has advantages such as clear separation of the two metals with high recovery.
In yet another object of the present invention the process is ecofi"iendly and the spent solutions obtained fi-om the electrolysis step can by recycled back to the system.
In yet another object of the present invention the purity of the copper and nickel powders produced is suitable to meet the P/M applications.
Novelty of the present invention is recovery and preparation of value added products viz electrolytic grade copper and nickel powder fi-om copper bleed electrolyte generated during the electro-refining of the impure copper produced in a copper plant. The main novelty of the invention is production of high purity P/M grade metal powders by partial decopperisation-crystallisation-solvent extraction-electrolysis which is no where cited in the literature.
In the process of present invention, the impurity laden copper bleed electrolyte generated from the electrolytic tank, which is periodically discarded from the system is partially decopperised to bring down copper level equal to the level of nickel and
then evaporated to crystallise mixed sulphates of copper and nickel. From the mixed solution containing copper and nickel sulphates, pH was adjusted and iron was removed by precipitation. This solution is then subjected to solvent extraction to separate copper and nickel, copper was stripped from the loaded organic as copper sulphate, and electrolysis of the copper sulphate from stripping operation and the nickel sulphate left un-extracted in the raffinate, to get pure copper and nickel powders. The copper and nickel powders thus produced possess desired purity for Powder Metallurgical (P/M) application.
Accordingly, the present invention provides an improved process for the preparation of copper and nickel powder from waste solution or stream containing copper and nickel which comprises:
(i) selecting the waste solution or stream containing copper and nickel and partially de-copperising the said copper bleed stream by electrolysis to bring down the copper level equal to nickel
(ii) evaporating the said solution to crystallise out mixed sulphate salts of copper and nickel.
(iii) leaching the mixed copper and nickel sulphate salts in aqueous medium at room temperature by maintaining the solid/liquid ratio in the range between 1/4 to 1/10 for a period of l-8h,
(iv) removing the impurities like iron from the mixed sulphate solution obtained in step (iii) by maintaining the pH in the range between 3-5 and precipitating thereof by the known method.
(v) separating copper and nickel from the purified mixed sulphate solution from step(iv) by solvent extraction using an organic substance having oxime / salicyldoxime as an active group diluted in kerosene, thus copper getting loaded in the organic phase leaving nickel in the raffinate.
(vi) stripping loaded copper from the organic phase by sulphuric acid solution.
(vii) electrolysis of the copper sulphate solution produced in step(vi) and nickel sulphate left un-extracted in the raffinate during solvent extraction to get pure copper and nickel powders.
(viii) washing and drying of the copper and nickel powder for P/M applications.
In an embodiment of the present invention, the waste solution or stream containing copper and nickel used may be selected fi-om the copper bleed electrolyte generated during the electro-refining of impure metal in the electrolytic tank in a copper producing industry having the composition range:
Cu = 30-60 g/L
Ni = 7-22 g/1
Bi = 0.0-0.3 g/L
Fe = 0.1-2.0 g/L
H2SO4 = 150-200 g/L
In another embodiment of the present invention the partially decopperised solution may have the composition range: Cu = 12-25 g/L Ni = 7-25 g/1 Bi = 0.0-0.3g/L Fe = 0.1-2.0 g/L H2SO4 = 160 -300 g/L
In still 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 80-100°C for different evaporation percentage ranging from 33-85%.
In yet another embodiment the mixed sulphate may have 8-15% Cu, 10-16% Ni, 0.1-1.0% Fe, 0.0 -0.06% Bi and 5-20g/L H2SO4 after washing with water and drying at a temperature varying from 70-100'C.
In still another embodiment of the present invention, the leach liquor employed for preparation of copper and nickel powder after iron removal by solvent extraction may be selected from the following composition range:
Cu = 5-15 g/L
Ni = 8-20 g/1
Fe = 0.0001-0.0004 g/L
Bi = 0-0.06g/L
pH = 0.1-3.0
In still another embodiment of the present invention copper and nickel powder may be prepared from the leach liquor containing mixed copper and nickel sulphate after their separation using 5-30% of an organic substance with oxime/salicyldoxime as the active group, diluted in kerosene. The organic/aqueous(0/A) is varied in the range 4/1 to 1/1 for a stirring period of 2-15 minutes on the bench scale(shake-out experiments).
In yet another embodiment of the present invention the metal powder is prepared from the separated copper and nickel sulphate of leach liquor in a continuous mode using a mixer- settler unit. A 5-30% organic reagent mentioned above in kerosene can be used to extract copper in 2-6 stages with 1-4 stages of scrubbing and 1-5 stages stripping with the spent electrolyte as stripping solution.
In yet another embodiment of the present invention the electrolytic grade copper powder is prepared from the strip solution from the solvent extraction step with the composition in the range 30-70g/L Cu, 0-0.99g/L Ni and 100-200g/LH2SO4, at the current density in the range 500-lOOOA/m^ in the electrolysis. Nickel powder is prepared by electrolysis of the raffinate solution with the composition range: 8-20g/L Ni, 0-0.4g/L Cu along with 10-60 g/L (NH4)2SO4, 0-15g/L H3BO3 and 0.01-0.5g/L thiourea in the pH range 3.5-9.0 while imparting current density in the range 3000-10,000 A/ml
In yet another embodiment of the present invention the copper and nickel powders prepared by the electrolysis of their respective sulphates is washed with water. Copper powder is then washed with a solution of a reducing agent to restrict oxidation of the
copper powder and dried at lOO^C to produce pure powder for P/M applications. The metal powders prepared may be of 99.93% copper and 99.8% nickel with a current efficiency varying in the range of 85.0-99% for copper and 45-65% for nickel respectively.
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 38.4g/L Cu, 19.4 g/L Ni, 0.76 g/L Fe, 0.2g/L Bi and 171.0 g/L H2SO4 was partially decopperised by electrowinning at a current density 100 A/m using 6% antimonial lead as insoluble anode and titanium sheet as cathode. A good quality of copper sheet of 99.5% purity was produced. The 950ml of the said decopperised solution comprising 17.9 g/L Cu, 20.4 g/L Ni, 0.76 g/1 Fe and 207 g/L H2SO4 was evaporated to produce mixed sulphate crystals of copper and nickel containing 8.39% Cu, 13.67% Ni and 0.50% Fe, 0.01%Bi and 20g/L H2SO4 with the volume of the mother liquor left to 210ml with 8.57g/L Cu, 6.72 g/L Ni, 0.25g/L Fe and 187g/L H2SO4 for recycling.
Mixed sulphate crystal was leached with water at solid / liquid ratio of 1/5 at room temperature producing leach liquor containing 8.39g/L Cu, 13.67g/L Ni & 0.6 g/L Fe. NaOH was then added to this leach liquor to raise pH to 3.6 followed by aeration to precipitate iron thereby giving clarified solution containing 8.4g/L Cu, 13.7g/LNi, 0.005g/L Fe. The said leach liquor was then used for solvent extraction using 25% LIX 84 in kerosene to separate copper from nickel at 0/A:l/l with a contact time of 5min in batch mode. Copper loaded organic was scrubbed by scrubbing solution with 1 .Og/L H2SO4 to remove entrapped nickel and finally stripped with 180g/L sulphuric acid solution to bring copper as sulphate into the aqueous solution. This copper sulphate solution containing 37.8g/L Cu, 0.08g/L Ni, trace Fe and 166g/L H2SO4 was then electrolysed at a current density of 600A/m^ to make copper powder. The raffinate containing nickel was adjusted to get lOg/L Ni, 0.006g/L Cu, 40g/L (NH4)2SO4 , 10 g/L H3BO3 and 0.2g/L thiourea, which on electrolysis at a current density of 4000A/m^ produced nickel powder.
The copper and nickel powders so formed were washed with water followed by treatment with a reducing agent to prevent the oxidation and dried at 100°C to get P/M grade powder of 99.9%Cu and 99.8%Ni.
Example-2
Copper bleed solution was subjected to partial decopperisation-crystallisation of mixed sulphate of copper and nickel-leaching and iron precipitation to get the iron free solution as mentioned in example 1. This leach liquor was then used for solvent extraction using 25% LIX 84 to separate copper from nickel in a mixer settler unit under continuous mode. About 99.8% copper was extracted in 4 stages leaving O.OOlg/L of Cu, 11.37%Ni in the raffinate. Loaded organic was scrubbed with dilute sulphuric acid (1.73g/L) to remove entrapped nickel in 2 stages and finally sfripped with stripping solution containing 30.25g/L Cu, 0.203g/L Ni and 179.34g/L H2SO4 in 2 stages to get copper sulphate solution. This solution containing 37.8g/L Cu, 0.6g/LNi and 166g/L H2SO4 was electrolysed at a current density of 800A/m^ to make copper powder. To the raffinate containing 11.37g/L Ni and traces of copper, 40g/L (NH4)2SO4, llg/L H3BO3 and 0.2g/L thiourea at pH 4.5 were added and was electrolysed at a current density of 6000A/m to get nickel powder.
The copper/nickel powder was washed with water followed by treatment with a reducing agent to prevent the oxidation of powder and dried at 100°C to get P/M grade powders of 99.93% Cu and 99.81% Ni..
Example-3
Copper bleed solution containing 39.9g/L Cu, 9.6g/L Ni, 0.69 g/L Fe and 194.04g/L H2SO4 was partially decopperised. A 990ml of the said decopperised solution comprising 17.75 g/L Cu, 9.4g/L Ni, 0.76g/L Fe and 200g/L H2SO4 was evaporated at 100°C to produce crystals of mixed sulphates of copper and nickel which on water washing had 11.06 % Cu, 12.46% Ni and 0.54% Fe, 0.045%Bi and 13.3%H2SO4.
The mixed sulphate crystal was leached in water at solid / liquid ratio of 1/5 at room temperature to produce leach liquor containing 11.0 g/L Cu, 12.5 g/L Ni and 0.5 g/L Fe. NaOH was added to this leach liquor to raise the pH to above 4.0 and was aerated thereby precipitating iron. The purified leach liquor containing 19.25 g/L Cu, 21.98 g/L Ni and 0.0004 g/L Fe was used for the solvent extraction of copper and nickel using 20% LIX84 in kerosene as an extractant. Bench scale simulation of copper and nickel extraction was done and about 99.8% of copper was extracted in 4 stages at an 0/A: 1.5/1 in a contact time of three min. leaving nickel in the raffinate solution. The scrubbing and stripping of the organic with Ig/L and 170g/L H2SO4 produced scrub and strip solution respectively. On electrolysis of copper sulphate from the strip solution containing 38g/L Cu, 0.1 g/L Ni, trace Fe and 160g/L H2SO4 at a current density of lOOOA/m^ copper powder was obtained. The raffinate containing 12g/L Ni. 0.004g/LCu was adjusted by making addition to get the solution with 45g/L (NH4)2SO4, 9g/L H3BO3 and 0.15g/L thiourea; which on electrolysis at a current density of 8000A/m^ produced nickel powder. The copper and nickel powders were washed and dried as mentioned in example 1. The purity of the metal powder was 99.93% Cu and 99.82% Ni.
Advantages
The main advantages of the present invention are:
1. The partial decopperisation in the first step produces good quality (99.93%) copper cathode which is salable.
2. The mother liquor obtained in the crystallisation step containing sulphuric acid can be recycled to the refinery for acid make-up.
3. The mixed metal sulphate crystal can be dissolved easily and the metals can be recovered with the help of solvent extraction in the desired form such as metal salt, cathode and electrolytic grade powder.
4. The preparation of copper and nickel powders by solvent extraction-electrolysis route has advantages such as clear separation of the two metals with high recovery.
5. The process is ecofriendly and the spent solutions obtained from the electrolysis step can by recycled back to the system.
6. In the present invention the purity of the copper and nickel powders produced 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 the preparation of copper and nickel powder from waste solution or stream containing copper and nickel
(i) selecting the waste solution or stream containing copper and nickel and partially de-copperising the said copper bleed stream by electrolysis to bring down the copper level equal to nickel (ii) evaporating the said solution to crystallise out mixed sulphate salts of copper and
nickel, (iii) leaching the mixed copper and nickel sulphate salts in aqueous medium at room temperature by maintaining the solid/liquid ratio in the range between ¼ to 1/10 for a period of 1-8 h, (iv) removing the impurities like iron from the mixed sulphate solution obtained in step (iii) by maintaining the pH in the range between 3-5 and precipitating thereof by the known method. (v) separating copper and nickel from the purified mixed sulphate solution from step(iv) by solvent extraction using an organic substance having oxime / salicyldoxime as an active group diluted in kerosene, thus copper getting loaded in the organic phase leaving nickel in the raffinate. (vi) stripping loaded copper from the organic phase by sulphuric acid solution, (vii) electrolysis of the copper sulphate solution produced in step(vi) and nickel sulphate
left un-extracted in the raffinate during solvent extraction, (viii) washing and drying of the copper and nickel powder for powder metallurgical [P/M] applications. 2. An improved process as claimed in claim 1 wherein the copper waste solution/stream employed is selected from the copper bleed stream generated during the electro-refining of impure metal in the electrolytic tank in a copper producing industry having the composition range:
Cu = 30-60 g/L Ni = 7-22 g/L Bi = 0.0-0.3 g/L Fe = 0.1-2.0 g/L H2SO4 = 150-200 g/L
3. An improved process as claimed in claims 1-2 wherein the partially decopperised solution
have composition range:
Cu= 12-25 g/L Ni = 7-25 g/1 Bi = 0.0-0.3g/L Fe = 0.1- 2.0 g/L H2SO4= 160-300 g/L
4. An improved process as claimed in claims 1-3 wherein mixed copper and nickel sulphate phases obtained by evaporation and crystallisation of the partially decopperised solution at temperature range 80 to 100°C, the mixed sulphate at different evaporation percentage ranging from 33-65% may have 8-15g/L Cu, 10-16g/L Ni, 0.1-1.0g/L Fe, 0.0-0.06%Bi and 5-20% H2SO4 after washing with water and drying at 80-100°C.
5. As improved process as claimed in claims 1-4 wherein the leach liquor employed for preparation of metal powder after iron removal, and separating copper and nickel by solvent extraction is selected from the following composition range:
Cu = 5-15 g/L
Ni= 8-20 g/1
Fe = 0.0001-0.0004 g/L
Bi=0.0-0.06g/L
pH = 0.1-3.0
6. An improved process as claimed in claims 1-5 wherein metal powder is prepared from the separated copper and nickel from the leach liquor using 5-30% LIX 84 in kerosene at organic/aqueous [O/A] ratio 4/1 to 1/1 for a stirring period of 2-15 minutes on the bench scale (shakeout experiments).
7. An improved process as claimed in claims 1-6 wherein metal powder is prepared from the separated copper and nickel sulphate of the leach liquor in a continuous mode using a mixer- settler unit.
8. An improved process as claimed in claims 1-7 wherein copper powder is prepared by electrolysis at the current density in the range 500-1000A/m2 of the strip solution in the composition range : 30-70 g/L Cu, 0.0-0.99gL Ni, 100-200g/L H2SO4 and nickel powder is produced at a current density of 4000-10,000A/m2 with the raffinate solution having the composition in the range: 8-20 g/L Ni, 0.0-0.04 g/L Cu, 10-60 g/L (NH4)2SO4, 0-15 g/L H3BO3 and 0.01-0.5g/L thiourea.
9. An improved process as claimed in claims 1-8 wherein copper and nickel powders
prepared by the electrolysis of their respective sulphate solutions are washed with water
followed by treatment with a reducing agent to restrict oxidation and dried at 100°C to
produce powders for powder metallurgical [P/M] applications, the metal powders prepared
is of 99.9% Cu and 99.8% nickel with a current efficiency varying in the range of 85.0-
99% for copper and 45-65% for nickel respectively.
10. An improved process for the preparation of copper and nickel powder from waste solution or stream containing copper and nickel is substantially described with reference to the examples.

Documents:

418-DEL-2004-Abstract-(24-08-2011).pdf

418-del-2004-abstract.pdf

418-DEL-2004-Claims-(24-08-2011).pdf

418-del-2004-claims.pdf

418-DEL-2004-Correspondence Others-(24-08-2011).pdf

418-del-2004-correspondence-others.pdf

418-del-2004-correspondence-po.pdf

418-del-2004-description (complete).pdf

418-del-2004-form-1.pdf

418-del-2004-form-18.pdf

418-del-2004-form-2.pdf

418-DEL-2004-Form-3-(24-08-2011).pdf

418-del-2004-form-3.pdf

418-del-2004-form-5.pdf

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Patent Number

250499

Indian Patent Application Number

418/DEL/2004

PG Journal Number

02/2012

Publication Date

13-Jan-2012

Grant Date

06-Jan-2012

Date of Filing

11-Mar-2004

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

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

PCT International Classification Number

C22B 3/14

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA