Simultaneous removal of antimony and arsenic by nano-TiO₂-crosslinked chitosan (TA-chitosan) beads

Antimony (Sb) and arsenic (As), carcinogenic and toxic elements, cause environmental pollution, in addition, the different chemical properties of Sb and As make them difficult to co-removal. In this study, we incorporated of nano-TiO₂ in the chitosan matrix to synthesized an efficient adsorption material nano-titania-crosslinked chitosan (TA-chitosan) beads, which was used to simultaneous removal of Sb and As from aqueous solution. TA-chitosan possesses a robust high removal performance for Sb and As under weakly acidic and neutral conditions; however, the removal is significantly inhibited under alkaline pH values. The adsorption kinetics of Sb and As on TA-chitosan conformed to the pseudo-second-order model, indicating that the removal of Sb and As was a chemical adsorption process. The adsorption isotherms of Sb(III/V) and As(III/V) on TA-chitosan follow the Langmuir model, and their maximum adsorption capacities are 70.19, 25.32, 64.52 and 102.89 mg·g^-1, respectively. The zeta potential showed that the surface of TA-chitosan was negatively charged over the full pH range upon Sb and As adsorption, demonstrating that negatively charged inner-sphere complexes were formed on TA-chitosan. This work may also provide a new perspective in titanium-chitosan material synthesis and heavy metal ions co-removal.