Synthesis of nano–silica and biogenic iron (oxyhydr)oxides composites mediated by iron oxidizing bacteria to remove antimonite and antimonate from aqueous solution: Performance and mechanisms.

Removal of antimony from wastewater is essential because of its potential harm to the environment and human health. Nano–silica and biogenic iron (oxyhydr)oxides composites (BS–Fe) were prepared by iron oxidizing bacteria (IOB) mediation and the batch adsorption experiments were applied to investigate antimonite (Sb(III)) and antimonate (Sb(V)) removal behaviors. By contrast, the synthetic BS–Fe calcined at 400 ℃ (BS–Fe–400) exhibited a large specific surface area (157.353 m2/g). The maximum adsorption capacities of BS–Fe–400 were 102.10 and 337.31 mg/g for Sb(III) and Sb(V), respectively, and experimental data fit well to the Langmuir isotherm and Temkin models, and followed the pseudo–second order kinetic model. Additionally, increasing pH promoted Sb(III) adsorption, while inhibited the adsorption of Sb(V), indicating that electrostatic attraction made a contribution to Sb(V) adsorption. Moreover, different co–existing ions showed different effects on adsorption. Characterization techniques of FTIR and XPS indicated that the main functional groups involved in the adsorption were –OH, C–O, C O, C–C, etc. and Sb(III) and Sb(V) may bind to iron (oxyhydr)oxides via the formation of inner–sphere complexes. The present work revealed that the synthetic BS–Fe–400 by nano–silica and biogenic iron (oxyhydr)oxides held great application potential in antimony removal from wastewater. [Display omitted] • A novel approach for the synthesis of Sb adsorbent was proposed. • Good dispersion and large specific surface area were observed in BS-Fe-400. • The synthesis of BS-Fe-400 mediated by IOB achieved high Sb adsorption capacity. • Surface complexation and inner–sphere complexation were the main mechanisms. • Redox reaction occurred during the adsorption process. [ABSTRACT FROM AUTHOR]