Recovery of zinc from wastes by hydrometallurgical processes

At present zinc is the most consumed metal after steel, aluminum and copper. Primary zinc sources are reducing because of the increasing interest to zinc. This situation necessitates the recovery of zinc from secondary hazardous zinc residues generated during production processes of zinc including products. About 30% of world zinc production is produced from secondary sources like brass, die casting scrap, flue dust, galvanizing residues and zinc sheet. In this study, recovery of zinc from flue dust by hydrometallurgical process is aimed by using brass flue dust supplied from a brass manufacturer. The effects of different parameters of leaching process, which is the first step of recovery, have been analyzed and the optimum leaching conditions are determined. In the experimental part of the study, leaching processes were carried out by using H2SO4, HCl and HNO3 at different temperatures (25, 50 and 75 oC) and in different time (15, 30, 60, 90 and 120 minutes). The effects of time, temperature, solid/liquid ratio, acid type and pH on the zinc leaching efficiency and the solution rate of copper were determined. Results of the experiments showed that highest zinc leaching performance was obtained by HNO3. The maximum zinc leaching efficiency was %90. And the optimum leaching conditions determined are 50oC temperature, 60 minutes of leaching time, 1/20 solid liquid ratio by using HCl. Because of the high amount of copper in the buffer solution, the copper percentages of the solutions were examined. And the highest copper solution rate was obtained by using HCl. After the leaching experiments, cementation experiments were done to purify the buffer solution. Keywords: Zinc flue dust, zinc recovery, leaching, cementation.