抄録
Selective recovery of different metal components such as copper, zinc and nickel from plating wastewater was studied by the precipitation of metal sulfides formed by sulfuration treatment. Three kinds of sulfurating agents: sodium sulfide (Na2S), sodium disulfide (Na2S2) and sodium tetrasulfide (Na2S4) were employed for sulfuration treatment of copper, zinc and nickel solutions. The sulfuration behavior and the precipitation characteristics of these metal sulfides were compared. It was found that the formation behavior of metal sulfide precipitates was dependent on pH value of the solution. For the sulfuration with Na2S, copper was first separated from the solution as copper sulfide at pH of 1.4-1.5, then zinc sulfide was precipitated at pH of pH 2.4-2.5. Subsequent precipitation of copper sulfide was followed by the precipitation of nickel and zinc sulfide in the residual solution at 5.5-5.6. The average specific filtration resistance of all cakes produced by sulfuration of Cu, Zn and Ni contained in solution with Na2S, Na2S2 and Na2S4 was smaller than that of metal hydroxide cake. A low average specific filtration resistance of the cakes produced by the sulfuration treatment was attributed to a larger particle size distribution of metal sulfides, depending on the sulfuration agents. It was also found that the compressibility coefficients of all metal sulfide cakes were smaller than that of metal hydroxide. The magnitude of compressibility coefficients produced by Na2S, Na2S2 and Na2S4 decreased in that order.
