Efficiency and mechanisms of antimony removal from wastewater using mixed cultures of iron-oxidizing bacteria and sulfate-reducing bacteria based on scrap iron

Treatment of antimony (Sb) mine drainage is generally regarded as a priority issue for regulatory authorities. In the study synergetic removal of Sb(V) from wastewater using cheap scrap iron inoculated with iron-oxidizing bacteria (JOB) and sulfate-reducing bacteria (SRB) was proposed. A strain of Enterobacter sp. (named as IOB-L), and Desulfovibrio sp. (named as GSRB) was first isolated separately, and Sb(V) removal performance in four different systems were investigated through batch experiment. It demonstrated that after 168 h of reaction, Sb (V) removal efficiency in iron + IOB + SRB system was 99.98%, which was higher than that in pure scrap iron, iron + JOB, and SRB system. SEM-EDX, XRD, and XPS analysis of reaction products indicated that scrap iron could be oxidized to amorphous Fe2O3 and FeOOH completely in biotic systems, providing favorable anaerobic condition for SRB. At the end of experiment, 80.35% of Sb(V) in iron + IOB + SRB system was adsorbed by biogenetic iron oxides, and 19.65% was bio-reduced as Sb2S3. Moreover, long-term treatment of antimony mine wastewater by scrap iron inoculated with IOB and SRB increased the bacterial abundance in the bioreactor, and Sb(V) removal ability of iron reached 180 mg(Sb)/g (Fe) after running for 310 days. The study provides an efficient method to remove Sb(V) from mine wastewater and might open a new way for the application of iron fillings.