アンミン銅（ＩＩ）存在下の亜鉛ダストのアンモニア浸出

Abstract

In the hot galvanizing process of steel pipe, so-called zinc dust, contaminated with small amounts of impurities like Fe, Pb and Cd, is generated as a by-product. Ammonia leaching is one of successful processes for recycling zinc dust. In order to improve productivity of the ammonia leaching process, dissolution behaviors of zinc have been investigated in the presence of amminecopper (II) oxidant with OCAL (Oxygen Circulating Ammonia Leaching) method.The experiments were carried out at 30-40°C and IONL/min oxygen in a 2-litter glass flask with leaching solution of 0-24g/L Cu (II), 0.5mol/L (NH4) 2CO3 and 1.0 mol/L NH3. It has been found that the dissolution rate of zinc remarkably increases with increasing Cu (II) concentration. Compared with the case in the absence of Cu (II), dissolution rate is speeded up more than 40 times for sheet zinc and more than 10 times for zinc dust in the presence of Cu (II). Further, it has found that the optimum molar ratio of zinc dust to Cu (II) in leaching solution is 1 to 1 for leaching of zinc dust and leaching rate remarkably decreases below or above this value. The dissolution reactions of zinc are proposed as follows.Zn+[Cu(NH3)4]2+→[Zn(NH3)4]2++CuCu+Cu[(NH3)4]2+→2Cu[(NH3)2]+4Cu[(NH3)2]++4NH3+4NH4++O2→4Cu[(NH3)4]2++2H2OFrom the results of this study, it has been proved that combing Cu (II) oxidant with OCAL method is very effective for improving the ammonia leaching process of zinc dust.