Method for Recovering Indium

Abstract

There is provided a method for recovering indium, the method being capable of recovering indium having a high purity at simple and inexpensive steps in a short time and with a high recovery. After indium containing substances, such as ITO target scraps, are crushed, the crushed substances are ground until the percentage of coarse particles having a larger particle size than a predetermined particle size is not larger than a predetermined percentage. Thereafter, the ground substances are dissolved in an acid, and the solution thus obtained is neutralized with an alkali so that the pH of the solution is 0.5 to 4. Then, the solution is aged at a temperature of 60 to 70° C. for 3 hours or longer to deposit and remove hydroxides of predetermined metal ions in the solution. Then, hydrogen sulfide gas is blown into the solution to deposit and remove sulfides of metal ions which are harmful to electrolysis at the subsequent step, and thereafter, the solution thus obtained is used as an electrolytic solution for electrowinning indium metal to recover indium having a high purity.

1 . A method for recovering indium, said method comprising:
 a grinding step of grinding an indium containing substance until the percentage of coarse particles of the indium containing substance is not larger than a predetermined percentage, the coarse particles having a larger particle size than a predetermined particle size;   a dissolving step of dissolving fine particles, which are obtained at the grinding step, in an acid;   a neutralizing step of adding an alkali to a solution after dissolution, which is obtained at the dissolving step, to neutralize the solution after dissolution so that the solution after dissolution has a pH of 0.5 to 4, to deposit and remove hydroxides of predetermined metal ions in the solution after dissolution;   an aging step of aging a solution after neutralization, which is obtained at the neutralizing step, at a predetermined temperature for a predetermined period of time;   a sulfurizing step of blowing hydrogen sulfide gas into a solution after aging, which is obtained at the aging step, to deposit and remove sulfides of metal ions; and   an electrowinning step of using a solution after sulfurization, which is obtained at the sulfurizing step, as an initial electrolytic solution to electrowin indium metal.   
     
     
         2 . A method for recovering indium as set forth in  claim 1 , wherein said predetermined particle size is 150 μm. 
     
     
         3 . A method for recovering indium as set forth in  claim 1 , wherein said predetermined percentage is 10%. 
     
     
         4 . A method for recovering indium as set forth in  claim 1 , wherein said predetermined temperature is in the range of from a room temperature to 80° C. 
     
     
         5 . A method for recovering indium as set forth in  claim 1 , wherein said predetermined period of time is not shorter than 2 hours. 
     
     
         6 . A method for recovering indium as set forth in  claim 1 , which further comprises a classification step of removing coarse particles having a larger particle size than said predetermined particle size by classification before said dissolving step after said grinding step. 
     
     
         7 . A method for recovering indium as set forth in  claim 1 , wherein said acid is selected from the group consisting of hydrochloric acid, sulfuric acid and nitric acid. 
     
     
         8 . A method for recovering indium as set forth in  claim 1 , wherein said indium containing substance is an ITO target scrap. 
     
     
         9 . Indium having a purity of not less than 99.999% and containing tin, the content of which is not larger than 0.5 ppm. 
     
     
         10 . Indium obtained by electrowinning which uses indium-tin-oxide as a raw material, and containing tin, the content of which is not larger than 0.5 ppm.