Antimonate reduction and immobilization with low sulfate generation dominated by cooperation of hydrogen and sulfur autotrophic reduction processes

Current biological strategies for removing Sb(V) face significant challenges. Sulfur-based autotrophic reduction (SAR) generates excessive sulfate, while hydrogen-based autotrophic reduction (HAR) does not achieve total Sb removal (TSb). This study developed a synergistic sulfur‑hydrogen autotrophic reduction (SHAR) process that integrated SAR and HAR to achieve efficient TSb removal from Sb(V)-contaminated water with low sulfate generation. The SHAR system achieved over 97 % removal efficiency of Sb(V) from water contaminated at 500 μg/L within 6 h, outperforming standalone SAR and HAR by 16–67 and 1.8–4.0 times, respectively. HAR and SAR separately contributed around 90 % and 8.0 %–11.3 % of Sb(V) reduction in the SHAR process. Notably, SHAR reduced sulfate production to just 2.3 % of the levels generated by sole SAR. This was accomplished by enhancing the abundance of sulfate-reducing genes and promoting the cooperative utilization of electron donors. Alkaline environments inhibited the precipitation of Sb(III) due to the dominance of HS⁻ and the high solubility of Sb precipitates. Additionally, the presence of nitrate and sulfate compromised the efficiency of Sb removal due to competition for electron donors. Solid-phase characterization using SEM-EDS, XRD, and XPS identified Sb₂O₃, Sb₂O₄ and Sb₂S₃ as the primary precipitates, ensuring stable immobilization of Sb. FTIR analysis indicated the involvement of functional groups (-OH, O-C=O, and -CH) in the sequestration of Sb. High-throughput technology analysis further identified Longilinea, Sulfuritalea, and Gemmobacter as key genera responsible for reducing Sb(V). This work offers a sustainable solution for treating Sb-contaminated water, achieving high-efficiency removal of Sb and reduced sulfate production.