Abstract：Secondary iron minerals were synthesized by A. ferrooxidans in the iron- and sulfate-rich acidic environment through shake flask incubation experiment in this study. The effect of 0, 50, 100, 200, or 400mg/L Ca2+ on pH, oxidation reduction potential (ORP), Fe2+ oxidation efficiency, total Fe precipitation efficiency, and secondary iron minerals phase in A. ferrooxidans incubation systems were investigated. The results showed that variation of pH, ORP, Fe2+ oxidation efficiency, and total Fe precipitation efficiency were similar during 0~24h incubation for all treatments. In the period of 24~108h, the more Ca2+ added in systems, the faster Fe2+ oxidation rate and the higher total Fe precipitation efficiency. When Ca2+ was added at 0, 50, 100, and 200mg/L, Fe2+ oxidation efficiency reached 100% at 84h and the corresponding total Fe precipitation efficiency was 27.0%, 29.7%, 33.9%, and 36.9%, respectively. While a complete oxidation was achieved in the presence of 400mg/L Ca2+ at 72h and total Fe precipitation efficiency reached up to 39.1 % at 108h. In this study, secondary iron minerals harvested from different systems were the mixture of schwertmannite and jarosite. The data obtained from this study will offer constructive meanings for understanding the secondary iron minerals bio-synthesis mechanism in the iron- and sulfate-rich acidic environment with Ca2+ existing.
