Cobalt powder production method

Abstract

Provided is a production method for producing coarse particles of high purity Co powder from a cobalt ammine sulfate complex solution using fine Co powder and using industrially inexpensive H 2 gas.

1 . A method of producing cobalt powder from a cobalt ammine sulfate complex solution derived from a cobalt-containing material, comprising:
 (1) a seed crystal addition step of adding cobalt powder as seed crystals to the cobalt ammine sulfate complex solution to form a mixed slurry;   (2) a reduction step of blowing hydrogen gas into the mixed slurry obtained in the seed crystal addition step to precipitate a cobalt component in the mixed slurry onto the seed crystals by hydrogen reduction reaction to form cobalt powder, and thereby to form a reduced slurry containing the cobalt powder;   (3) a growth step of adding the cobalt ammine sulfate complex solution to the cobalt powder obtained by solid-liquid separation of the reduced slurry formed in the reduction step (2) to form a slurry, blowing hydrogen gas into the resulting slurry, and reducing, precipitating, and growing a cobalt component in the slurry on a surface of the cobalt powder by hydrogen reduction reaction to form a grown cobalt powder, and thereby to form a slurry containing the grown cobalt powder; and   (4) a recovery step after the reduction step of subjecting the reduced slurry containing the cobalt powder obtained in the reduction step (2) to solid-liquid separation to separate and recover the cobalt powder as a solid phase component, and another recovery step after the growth step of subjecting the slurry containing the cobalt powder obtained in the growth step (3) to solid-liquid separation to separate and recover the cobalt powder as a solid phase component.   
     
     
         2 . The method of producing cobalt powder according to  claim 1 , wherein, in the seed crystal addition step (1), a dispersant is further added to the mixed slurry when the seed crystals are added to the cobalt ammine sulfate complex solution to form the mixed slurry. 
     
     
         3 . The method of producing cobalt powder according to  claim 1 , wherein, in the seed crystal addition step (1), an amount of the seed crystals added is 1 to 200% by weight with respect to the weight of cobalt in the cobalt ammine sulfate complex solution. 
     
     
         4 . The method of producing cobalt powder according to  claim 1 , wherein the cobalt ammine sulfate complex solution is obtained by:
 a leaching step of dissolving the cobalt-containing material containing nickel and impurities;   a nickel separation step of adjusting a pH of the leachate containing cobalt, nickel, and impurities and obtained in the leaching step and then separating the leachate into a crude cobalt sulfate solution and a nickel recovery solution by solvent extraction;   a solution purification step of removing the impurities from the crude cobalt sulfate solution obtained in the nickel separation step by any one or a combination of solvent extraction, a sulfurization method, and a neutralization method to obtain a cobalt sulfate solution; and   a complexing step of subjecting the cobalt sulfate solution to complexing treatment with ammonia.   
     
     
         5 . The method of producing cobalt powder according to  claim 4 , wherein the cobalt-containing material is at least one of cobalt and nickel mixed sulfide, crude cobalt sulfate, cobalt oxide, cobalt hydroxide, cobalt carbonate, and metallic cobalt powder. 
     
     
         6 . The method of producing cobalt powder according to  claim 4 , wherein 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester or di-(2,4,4-trimethylpentyl)phosphinic acid is used as a solvent in the solvent extraction of the solution purification step and the nickel separation step. 
     
     
         7 . The method of producing cobalt powder according to  claim 1 , wherein, in the seed crystal addition step (1), the cobalt ammine sulfate complex solution has an ammonium sulfate concentration of 100 to 500 g/l, and an ammonium concentration of 1.9 or more by mole with respect to a cobalt concentration in the cobalt ammine sulfate complex solution. 
     
     
         8 . The method of producing cobalt powder according to  claim 1 , wherein, regarding the hydrogen reduction reaction in the reduction step (2) and the growth step (3), hydrogen reduction is performed by maintaining a temperature of 120 to 250° C. and a pressure of 1.0 to 4.0 MPa. 
     
     
         9 . The method of producing cobalt powder according to  claim 2 , wherein the dispersant comprises one or more of an acrylate and a sulfonate. 
     
     
         10 . The method of producing cobalt powder according to  claim 1 , further comprising:
 a cobalt powder briquetting step of processing the cobalt powder having high purity and obtained in the growth step (3) into cobalt briquettes in a block form using a briquetting machine; and   a briquette sintering step of sintering the resulting cobalt briquettes in the block form under a condition of maintaining a temperature of 500 to 1200° C. in a hydrogen atmosphere to form cobalt briquettes as a sintered compact.   
     
     
         11 . The method of producing cobalt powder according to  claim 1 , further comprising an ammonium sulfate recovery step of concentrating a solution after reaction obtained by separating the cobalt powder as the solid phase component by the solid-liquid separation in the recovery steps (4) after the reduction step (2) and the growth step (3), to precipitate ammonium sulfate to recover ammonium sulfate crystals. 
     
     
         12 . The method of producing cobalt powder according to  claim 1 , further comprising an ammonia recovery step of adding an alkali to a solution after reaction obtained by separating cobalt powder as the solid phase component by the solid-liquid separation in the recovery steps (4) after the reduction step (2) and the growth step (3), and heating the resulting mixture to volatilize and recover ammonia gas. 
     
     
         13 . The method of producing cobalt powder according to  claim 4 , wherein the ammonia recovered in the ammonia recovery step is recycled in production processes in the method of producing the cobalt powder, and used as an alkali for pH adjustment in the nickel separation step, as an alkali for neutralization when the neutralization method is used in the solution purification step, and as an alkali used in the complexing step 4. 
     
     
         14 . The method of producing cobalt powder according to  claim 4 , wherein the seed crystals of the cobalt powder in the seed crystal addition step (1) is cobalt powder formed by adding a reducing agent to the cobalt sulfate solution obtained in the solution purification step 4. 
     
     
         15 . The method of producing cobalt powder according to  claim 4 , wherein the seed crystals of the cobalt powder in the seed crystal addition step (1) is cobalt powder formed by hydrogen reduction reaction in which an insoluble solid is added to the cobalt ammine sulfate complex solution obtained in the complexing step 4 and hydrogen gas is blown into the resulting mixture at high temperature and high pressure. 
     
     
         16 . Cobalt briquettes obtained using the methods of  claim 1 .