Modification of the biochar platform with organic reagents could enrich active functional groups, and incorporation of magnetic mineral on it could facilitate separation from the aqueous solution after practical application. The present research took advantage of both by performing -NO2 grafting and MnOx loading binary modification on biochar derived from bagasse. The results demonstrated that the binary modification dramatically enhanced the antimonite (Sb(III)) adsorption ability of the sole-modified biochar. The Sb(III) sorption experiment revealed the optimal binary modified parameters were 300 degrees C pyrolysis temperature and the reagent doses of 2.0 g urea, 1.0 g NaOH, 1.5 mL CCl4, 2.0 g NaNO2, and 0.1 g KMnO4. Binary-modified biochar synthesized under the optimal condition (MNBC300) could efficiently remove Sb(III) in the aqueous solution with an adsorption amount of 142.86 mg/g, which was much higher than that of the sole (27.70 and 13.43 mg/g). At a fast rate, the Sb(III) sorption behavior was governed by multilayer heterogeneous chemisorption adsorption via the complexation between-NO2/Mn-O bond and Sb(III). Fitting peaks on X-ray photoelectron spectra (XPS) demonstrated the oxidizability of MNBC300 due to the electron transfer from Sb(III) to Mn3+, which was thereby oxidizing Sb(III) to less toxic Sb(V). Overall, the present study showed a novel biochar modification technique to eliminate the ecological and human health hazards of Sb-containing wastewater.
