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 anerobic oxidation of elemental sulfur (S0). Sb(V) was reduced to Sb(III) by autotrophic bacteria using S0 as electron donor; meanwhile, S0 disproportionation, which produced sulfide and SO42-, occurred under anerobic condition in the S0-based bio-system. Afterwards, Sb(III) reacted with sulfide to form Sb(III)-S precipitate, achieving an effective Sb removal. SEM-EDS, XPS, XRD and Raman spectrum identified that the precipitate was Sb2S3. Higher SO42- generation than the theoretical value of 0.26 g SO42-/g (Sb(V) reduction to Sb(III)) confirmed the occurrence of S0 disproportionation. In addition, co-existing nitrate inhibited Sb removal as nitrate is the favored electron acceptor over Sb(V). In contrast, co-existing SO42- promoted Sb(V) reduction and precipitate formation via enhancing sulfide generation by sulfate reduction. Illumina high-throughput sequencing analysis revealed that Metallibacterium, Citrobacter and Thiobacillus might be responsible for Sb(V) reduction and S0 disproportionation. This study provides a promising approach for the remediation of Sb(V)-contaminated water