Impact of Iron(II) Concentration and Sequential Addition of Metal(loids) on the Removal of Aqueous Antimony and Arsenic <?A3B2 pi6?>Through Microbial Sulfate Reduction

<p indent="0mm"> Different Fe²⁺ concentrations (10, 20, 50, 100, 200 and <sc>500 mg/L),</sc> antimony (Sb), and arsenic (As) species (i.e. Sb(V) + As(V) and Sb(III) + As(III), <sc>5 mg/L)</sc> were introduced to batch experiments of microbial sulfate reduction at different intervals. The changes in physicochemical parameters such as pH, redox potential (Eh), total alkalinity, SO₄²⁻, sulfides, and variations in Fe, Sb, or As concentrations were analyzed at <sc>0.5 h</sc> and on the 7^th day after Sb and As addition to elucidate the effects of Fe²⁺ concentrations and the adding sequence of Fe²⁺, Sb and As on the efficiency and mechanisms of microbial sulfate reduction to remove aqueous Sb and As. Results indicated that compared to the adding sequence, Fe²⁺ concentration had a more significant impact on the removal efficiency. Lower Fe²⁺ concentrations <sc>(≤20 mg/L)</sc> did not promote As removal. In comparison, higher Fe²⁺ concentrations <sc>(≥50 mg/L)</sc> significantly improved As removal efficiency. Antimony removal exceeded 95% for all treatments, so the effects of adding sequences and Fe²⁺ concentrations on Sb removal were challenging to delineate. When treating Sb and As containing wastewater through microbial sulfate reduction, the addition of Fe²⁺ should be considered to enhance removal efficiency. Similarly, the environmental behavior of Fe-bearing minerals needs to be better considered when treating Sb- and As-contaminated sediments or soils by enhanced microbial sulfur reduction to achieve more significant remediation results.