Antimonate reduction and immobilization driven by pyrite and woodchips-based abiotic and biotic processes

Abstract

Antimony (Sb) pollution in aquatic environments poses severe threats to ecological safety and human health due to its high toxicity. Four reaction systems were constructed in this study, including a pyrite abiotic reactor (PAR), a pyrite-woodchips abiotic reactor (PWAR), a pyrite biotic reactor (PBR), and a pyrite-woodchips biotic reactor (PWBR), to systematically investigate the Sb(V) removal performance in various systems. The results showed that PAR achieved limited Sb(V) removal efficiencies of 56.4%–57.6% at a hydraulic retention time (HRT) of 12 h with an initial Sb(V) of 10 mg/L. In contrast, microbial inoculation improved Sb remediation performance, and woodchips amendment further optimized the reaction microenvironment. The PWBR obtained Sb(V) and total Sb removal efficiencies of >90% in the first 20 days, and final stabled at 69.3% and 64.5% with HRT = 12, respectively. SEM and XPS analysis identified the generation of Sb-O, Sb-S, and Fe-O-Sb precipitation. Woodchips acted as a slow-release carbon source and biofilm carrier, fueling microbial tricarboxylic acid (TCA) cycle metabolism and stimulating the proliferation of functional bacteria, including Candidatus Competibacter , Ignavibacterium , Desulfobacterium , Geobacter , and Shewanella . Functional gene prediction confirmed that woodchips significantly upregulated genes involved in carbon metabolism, sulfate reduction, and iron transport, accelerating the coupled Fe 2+ /Fe 3+ and S cycles. Abiotic Sb removal mainly depended on pyrite-mediated chemical reduction and adsorption, while biotic processes further strengthened pyrite dissolution, electron donor supply, and Sb-S precipitate formation. This study provides a reliable theoretical basis and technical reference for efficient Sb immobilization in the presence of Fe, S and C.