Promotion of higher synthesis temperature for higher-efficient removal of antimonite and antimonate in aqueous solution by iron-loaded porous biochar

Abstract

Iron-loaded porous biochar (FPBC) was synthesized by co-pyrolysis method using sawdust and potassium ferrate at 500 (FPBC500) and 800°C (FPBC800), then characterized and applied to eliminate antimonite (Sb(III)) and antimonate (Sb(V)) in aqueous. Due to alkali erosion on feedstock and K/Fe-oxides attacking carbon, FPBC800 obtained a larger specific surface area (SSA) (515.49 m2·g−1) that was 5.48-fold that of PFBC500, meaning the exposure of more active sites. Fe3O4 was formed on FPBC500, but Fe0 and Fe3C were generated on FPBC800. FPBC800 showed the optimal sorption performance for Sb(III) (144.48 mg·g−1) and Sb(V) (45.29 mg·g−1), which were much higher than that of FPBC500. Noteworthily, Sb(III) anchored on FPBC was oxidized to Sb(V) with less ecotoxicity; moreover, FPBC800 with Fe0 showed stronger oxidization. Although pH-dependent sorption of Sb(III)/Sb(V) on FPBC occurred, the resistance to environmental factors showed a potential for eliminating actual pollution, demonstrating an easy-to-operate construction strategy for modified biochar.