Study On Preparation Of Electrolysis Silver Powder From Copper Anode Slime

Copper anode slime is composed of precious metals such as selenium, copper, gold, platinum, palladium, silver and so on. In this paper, the research on recovering precious metals from copper anode slime and preparing electrolytic silver powder are reviewed. Recovering precious metals and the electrolysis technology of silver powder prepared from the silver anode plate are studied in detail. New ways of the re-use of secondary resources and environmental protection are developed. At the same time, a new technology of preparing high purity fine silver powder has been proposed, which has a certain academic value and application prospect.In this paper, the process of recovering precious metals from copper anode slime and electrolysis silver powder are proposed. First, roasting anode slime and volatilizing selenium with concentrated sulfuric acid. Second, leaching copper by concentrated sulfuric acid. Third, leaching gold, platinum, palladium with chlorates, and then leaching silver with ammonia. Finally, preparing the fine silver powder by electrolysis.Selenium is recycled by roasting copper anode slime with concentrated sulfuric acid. And the effect of acid and slime ratio, roasting temperature and time, volatilizing selenium temperature and time on selenium recovery has been studied. The optimal conditions of volatilizing selenium process are as follows: acid and slime ratios （weight ratio） （0.8～1.0）:1, roasting temperature at 250～300℃for 3.5h, steaming selenium at 600～700℃for 11h.The recovery rate of selenium can be more than 95%.Copper is leached with sulfuric acid from the selenium volatilized residue. The effect of the liquid and solid ratio, content of sulfuric acid, leaching temperature and time on copper recovery has been studied. The optimal conditions are as follows: liquid and solid ratio 1:（3～5）, sulfuric acid 120～140g/L, leaching temperature at 90～95℃for 4.5h. The recovery rate of copper can reach 99%.Gold, platinum, palladium are leached with chlorates from the copper leached residue. The effect of liquid and solid ratio, content of sulfuric acid, content of sodium chloride, leaching temperature and time on the leaching rate has been studied. The optimal conditions are as follows: liquid and solid ratio 1:（4～6）, sulfuric acid 130～150g/L, sodium chlorate 10～15g/L, leaching temperature at 90～95℃for 4.5h. The leaching rate of gold is more than 98% and the leaching rate of platinum and palladium can reach 85% respectively.Silver is leached with ammonia from the gold leached residue. The effect of liquid and solid ratio, content of ammonia, leaching time on the leaching ratio has been studied. The optimal conditions are as follows:liquid and solid ratio 1:（4～6）, ammonia 80～100g/L, leaching time for 5h. And the leaching rate of silver can reach more than 98%.High purity silver powder with branch-like structure was prepared in HNO₃+AgNO₃ aqueous solution by galvanostatic electrolysis. The effects of electrolyte composition and electrolysis factors on electrocrystallization process were investigated with X-ray diffractometer （XRD） and electrochemical techniques. The results show that the appropriate concentration of HNO₃ is 10g L-1, the grain size of silver powder is 56.4nm. The concentration of AgNO₃ has little effect on silver electrocrystallization. The electrodeposition rate of silver powder can be improved when reducing deposition potential or increasing electrolysis temperature. It appears that the addition of additive can remarkably enhance the nucleation rate, which leads to form finer silver powder.