Abstract：The inoculation of Acidithiobacillus ferrooxidans and the addition of Fe2+ as their substrates accelerated the solubilization of Zn, Cu and Cr from sewage sludge. However, a decrease in Cu removal from 91% to 60% with time elapse could be observed in the late process, which appeared simultaneously with the formation of jarosite resulting from hydrolysis of Fe3+. The tested jarosite was synthesized by using bacterial oxidation of Fe2+ by resting A. ferrooxidans in acid solution (pH 2.5) under conditions stimulating sludge bioleaching. Adsorption edge measurement showed that only less than 9% of Cu2+ was adsorbed onto jarosite in the pH range of 2.0-2.5, indicating that adsorption mechanism could not explain fully re-sorption of Cu2+ (about 31%) in the anaphase of bioleaching process. In the coprecipitation studies, when jarosite was precipitated in the presence of Cu2+ (10 mg·L-1), a significant amount of Cu (44.6%) was incorporated into the precipitate. Coprecipitation of jarosite with Cu2+ was the predominant process by which soluble Cu was partially re-sorpted by jarosite in the anaphase of bioleaching process.
