Optimization of Ni, Cu and Zn Recovery in Bioleaching of Electronic Scrap

Abstract

Bioleaching was applied to mobilize metals from printed wire boards (PWBs). PWBs have a rich metal content and are produced in high volume. Operating conditions of bioleaching of PWBs using an adapted mixed culture of Acidithiobacillus ferrooxidans (A. ferrooxidans) and A. thiooxidans to recover Cu, Zn and Ni were optimized in this study. The adaptation phase began at 1 g/L PWBs powder with 10% inoculation and the final pulp density was 20 g/L after about 40 days. Optimization was performed using central composite design method to optimize four effective factors, including initial pH (1.5 to 2), pulp density (15 to 25 g/L), initial sulfur (3 to 7 g/L) and initial FeSO4 (15 to 25g/L), to achieve maximum recoveries of Cu, Zn and Ni. Also, the present study evaluated the effect of the independent variables initial pH, pulp density, initial Fe3+ concentration and initial sulfur content on extraction of metals from PWBs. Results showed that with an initial pH of 1.5, 25g/L pulp density, 25 g/L of FeSO4·7H2O and 7 g/L of S0, copper, zinc and nickel recoveries reached 92%, 96% and 94%, respectively, after 25 days.