Selective recovery of copper, zinc and nickel from electroplating wastewater was studied by precipitating the metal sulfides formed by sulfuration treatment. CuSO4, ZnSO4 and NiSO4 involved in model solutions and those of plating wastewater were adjusted to 100-120mg dm−3 of the initial metal concentration. Two kinds of sulfurating agents, sodium sulfide (Na2S) and sodium hydrosulfide (NaHS) of 6.8×10−2 mol dm−3, were employed.
As a result, it was found that Na2S was more effective for the separation of the metal sulfides precipitated. The formation of metal sulfides was dependent on the pH value of the solution. In the sulfuration process using Na2S, copper was first separated from the solution as copper sulfide in pH1.4-1.5, followed by the formation of zinc sulfide in pH2.4-2.5. Subsequently, nickel sulfide was precipitated after the formation of copper and zinc sulfides in the residual solution in pH5.5-6.0.
The same results of the formation behavior of copper sulfide, zinc sulfide and nickel sulfide in a simulated plating solution were obtained for those in an electroplating solution.
