Recovery of nickel from spent electropla

Recovery of nickel from spent electro nickel plating solution has been investigated via hydrometallurgical and electrometallurgical processes. Experimental consisted of 3 steps, including precipitation of nickel from spent solution, leaching of nickel precipitate, and electrowinning of nickel. Nickel precipitation was performed using sodium hydroxide. Leaching parameters such as 1 M to 3 M sulfuric acid concentration, 100 g⋅L-1 to 300 g⋅L-1 solid to liquid ratio, and 30 min to 180 min leaching time were investigated. The leachate from the optimal leaching condition was further used as an electrolyte in electrowinning process. Effects of 3.3 V to 3.7 V cell voltage on recovery and purity of nickel and current efficiency of the electrowinning process were investigated. The results showed that nickel precipitation could be performed by using 2 M sodium hydroxide to adjust the solution to pH ≥13. For leaching, dissolution of nickel precipitate of higher than 90% was achieved at the optimum leaching condition of 2 M sulfuric acid, solid to liquid ratio of 100:1 g⋅L-1 and leaching time of 60 min. Electrowinning of nickel applying the cell voltage of 3.5 V for 24 h showed the greatest nickel recovery of about 61%, giving nickel purity of 99% while the current efficiency of electrowinning cell of approximately 16% can be achieved.