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

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 m 2 ·g −1 ) that was 5.48-fold that of PFBC500, meaning the exposure of more active sites. Fe 3 O 4 was formed on FPBC500, but Fe 0 and Fe 3 C 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 Fe 0 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.