Manganese oxide-modified biochar derived from discarded mushroom-stick for the removal of Sb(III) from aqueous solution

In this study, discarded mushroom-stick, which is widely available, was selected as a precursor to prepare MnO 2 -modified biochar (MBC) for Sb(III) removal. Several characterisation methods (SEM, BET, XPS, FT-IR, and XRD) were used to explore the mechanisms of antimony adsorption onto MBC. The results showed that MBC is a mesoporous material with a fluffy structure and a higher specific surface area (23.56 and 32.09 m 2 ·g −1 ) than PBC600 (13.62 m 2 ·g −1 ), exhibiting superior and stable adsorption capacities for Sb(III) (50.30 mg·g −1 for 1/30MBC600 and 64·12 mg·g −1 for 1/20MBC600) across a wide pH range (pH 4–8). X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopy analyses indicated that the main oxides and functional groups involved in the adsorption were manganese oxides and hydroxyl groups. Forty-four per cent of the adsorbed Sb(III) was oxidised to Sb(V) by manganese oxides or hydroxyl groups both on the surface of biochar and in solution. According to adsorption kinetics and isotherms, the adsorption process of Sb(III) is chemisorption, which includes monolayer and multilayer heterogeneous chemisorption processes. To sum up, MBC is an excellent adsorbent for the capture of Sb(III) from contaminated water with strong potential for future application.