Sb(V) Reduced to Sb(III) and More Easily Adsorbed in the Form of Sb(OH) 3 by Microbial Extracellular Polymeric Substances and Core–Shell Magnetic Nanocomposites

Antimony (Sb) is a priority pollutant. Reduction adsorption is an effective treatment, because Sb(III) is easier to remove than Sb(V). However, it is unclear what specific ionic form is prone to be adsorbed. In this study, microbial extracellular polymeric substances (EPS) and magnetic nanocomposite EPS@Fe 3 O 4 were first used in the simultaneous reduction and adsorption of Sb(V). The relevance between adsorbent and ionic forms was investigated. EPS achieved high Sb adsorption capacity (120 mg/g) and EPS@Fe 3 O 4 (216 mg/ (g EPS)) performed better due to great dispersibility. The pseudo-second-order kinetic model and the Redlich-Peterson model fit the results best, suggesting a chemical adsorption process. According to XPS and FTIR analysis, Sb(V) was reduced to Sb(III) by anilino, hemiacetal hydroxyl, and phenolic hydroxyl on EPS and EPS@Fe 3 O 4, accompanied by the chelation of hydroxyl. Repetitive adsorption–desorption experiments displayed a great recycling property of EPS@Fe 3 O 4 . This work provides new ideas for Sb(III) detection through analyzing the relationship among the zeta potential of EPS, Sb ionic forms, and adsorption capacity. It is important to demonstrate EPS and EPS@Fe 3 O 4 as potential reducing adsorbents to remediate Sb contaminated waters.