Ammoniacal leaching behavior and regularity of zinc ash

Abstract In this work, a new hydrometallurgical process was developed to treat zinc ash produced from the hot galvanizing industry. The theoretical analysis shows the feasibility of dissolving zinc ash in the NH3–NH4Cl–H2O system, and the dissolution products are predominantly composed of Zn (NH3)42+. The impacts of different experimental conditions were examined, and the leaching ratio of zinc was as high as 96.4% under the conditions of NH3/NH4+ ratio of 1:1, liquid/solid of 9:1, total ammonia concentration of 8 mol/L and the stirring speed of 250 rpm at 313 K for 120 min. The kinetics of the leaching process were investigated and the calculated apparent activation energy was approximately 4.69 kJ/mol, which indicated that the zinc ash leaching process was controlled by diffusion-controlled. As revealed by the determination of impurity ions, on one hand, there were fewer impurities in the leaching solution, and the concentrations of Fe2+ and Pb2+ in solution are less than 0.02 mg/L and 0.05 mg/L respectively; on the other hand, there was no need for further impurity removal in this process. The proposed process has a certain application value in treating zinc ash.