Synthesis of magnetic biochar from pine sawdust via oxidative hydrolysis of FeCl2 for the removal sulfamethoxazole from aqueous solution.

Magnetisation of carbonaceous adsorbent using iron oxide (FexOy) has potential to decrease the recovery cost of spent adsorbent because it could be separated magnetically. However, formation of various phases of FexOy and iron hydroxide (Fex(OH)y) during synthesis particularly the non-magnetic phases are difficult to control and could significantly reduce the magnetic saturation of the adsorbent. Hence, formation of the most magnetic FexOy, Fe3O4, on biochar via oxidative hydrolysis of FeCl2 under alkaline media was performed to synthesise magnetic adsorbent using pine sawdust biochar (magnetic pine sawdust biochar: MPSB). The Fe3O4 nanoparticles on the surface of biochar contributed to high saturation magnetisation of MPSB, 47.8Am2/kg, enabling it to be separated from aqueous solution using a magnet. MPSB were examined physically and chemically using various techniques. Sorbent-stability, parametric, kinetics, isotherm, thermodynamic and sorbent-regeneration studies were performed to comprehend the potential of MPSB as adsorbent to remove an emerging contaminant, sulfamethoxazole (SMX) from aqueous solution. Results showed that MPSB was stable within solution pH 4-9. Adsorption of SMX onto MPSB was favourable at low pH, fast and best described by Redlich-Peterson model. Adsorption was exothermic with physisorption possibly due to hydrophobic interaction and spent adsorbent could be regenerated by organic solvents.