Leaching of zinc ash with hydrochloric acid solutions

Abstract

Fine-grained fraction (<1.25 mm) of industrial zinc ash was characterized in terms of chemical and phase compositions as well as leaching behaviour in hydrochloric acid solutions. Waste product contained about 55% Zn, 14% Cl, and less than 0.4% of other metals (Fe, Pb, Al, etc.). It was a mixture of metallic zinc, simonkolleite, zinc oxide, and zinc hydroxide chloride. Dissolution of metals from the zinc ash was determined depending on the solid-to-liquid ratio (1:80-1:20), acid concentration (0.23-2.0 M), and temperature (20-60ºC). The best results (almost 100% zinc recovery) were obtained for 2M HCl at 20ºC, S:L ratio 1:20, and leaching time 30 min. The final solutions were contaminated mainly by iron and lead ions (both below 0.15 g/L). Further treatment of the solution to obtain metallic zinc or zinc chloride was also proposed.