Enhanced biological antimony removal from water by combining elemental sulfur autotrophic reduction and disproportionation

Antimony (Sb), a toxic metalloid, has serious negative effects on human health and its pollution has become a global environmental problem. Bio-reduction of Sb(V) is an effective Sb-removal approach. This work, for the first time, demonstrates the feasibility of autotrophic Sb(V) bio-reduction and removal coupled to anaerobic oxidation of elemental sulfur (S-0). In the S-0-based biological system, Sb(V) was reduced to Sb(III) via autotrophic bacteria by using S-0 as electron donor. Meanwhile, S-0 disproportionation reaction occurred under anaerobic condition, generating sulfide and SO42- in the bio-systems. Subsequently, Sb(III) reacted with sulfide and formed Sb(III)-S precipitate, achieving an effective total Sb removal. The precipitate was identified as Sb2S3 by SEM-EDS, XPS, XRD and Raman spectrum analyses. In addition, it was found that co-existing nitrate inhibited the Sb removal, as nitrate is the favored electron acceptor over Sb(V). In contrast, the bio-reduction of co-existing SO(4)(2-)enhanced sulfide generation, followed by promoting Sb(V) reduction and precipitation. Illumina highthroughput sequencing analysis revealed that Metallibacterium, Citrobacter and Thiobacillus might be responsible for Sb(V) reduction and S-0 disproportionation. This study provides a promising approach for the remediation of Sb(V)-contaminated water.

Automated summary

This study demonstrates the feasibility of autotrophic Sb(V) bio-reduction and removal coupled to anaerobic oxidation of elemental sulfur (S-0) for the first time. The results show that Sb(V) can be effectively reduced to Sb(III) by autotrophic bacteria using S-0 as electron donor, and Sb(III) then reacts with sulfide to form an Sb(III)-S precipitate, achieving efficient total Sb removal. The presence of nitrate inhibits Sb removal, while co-existing sulfate enhances sulfide generation and promotes Sb reduction and precipitation.