2006 年 57 巻 1 号 p. 77
Selective recovery of copper, zinc and nickel from electroplating wastewater was studied by investigating the sulfuration behaviors of these metal components and the filtration characteristics of the metal sulfides produced. As model metal solutions, CuSO4, ZnSO4 and NiSO4 aqueous solutions of 100mg/dm3 initial concentrations were employed. Three kinds of sulfurating agents : sodium sulfide (Na2S), sodium disulfide (Na2S2) and sodium tetrasulfide (Na2S4) of 6.8×10−2mol/dm3 were used. For selective sulfuration of CuSO4, ZnSO4 and NiSO4, the sulfurating agent was added to the metal solutions, adjusting the pH of these solutions at pH=1.4-1.5, 2.4-2.5 and 5.5-6.0, respectively.
As a result, it was found that Na2S was most effective for selective sulfuration of copper, zinc and nickel. The sulfuration behaviors of copper, zinc and nickel in electroplating wastewater were almost the same as those in model solutions.
Furthermore, the filtration characteristics such as the average specific filtration resistance and the compressibility coefficients of the metal sulfide produced with different sulfurating agents were measured. It was recognized that the average specific filtration resistance of the metal sulfides produced with different sulfurating agents was different. It was also found that the compressibility coefficient of the metal sulfides was lower than that of metal hydroxide. The compressibility coefficient of the metal sulfides decreased in the order of Na2S, Na2S2 and Na2S4.