Magnetic durian shell biochar-based activators for high-efficient activated peroxymonosulfate removal of carbamazepine in wastewater treatment process

ABSTRACT Schematic illustration of the synthesis of CoFe₂O₄-modified biochar from durian shell using FeCl₃·6H₂O and CoCl₂·6H₂O, followed by PMS activation for carbamazepine (CBZ) degradation. Reactive oxygen species generated on the catalyst surface attack CBZ, leading to its oxidation and eventual mineralization into CO₂ and H₂O. Waste-derived biochar has emerged as a sustainable and low-cost catalyst for peroxymonosulfate (PMS) activation; however, its practical application is often hindered by insufficient active sites, limited catalytic efficiency, and poor recoverability. To address these challenges, a magnetic modified biochar (CFBC) was synthesized by anchoring CoFe2O4 nanoparticles onto durian shell-derived biochar and applied for carbamazepine (CBZ) degradation via PMS activation. The effects of pyrolysis temperature and CoFe2O4 loading on catalyst properties and catalytic performance were systematically evaluated. The optimized catalyst, CFBC-8, exhibited outstanding catalytic activity, achieving 89.91% CBZ removal within 15 min under PMS activation, which was substantially higher than that of pristine biochar. The enhanced performance was attributed to the synergistic interaction between CoFe2O4 nanoparticles and the biochar matrix, which promoted PMS activation and reactive species generation. Increasing catalyst dosage and PMS concentration accelerated CBZ degradation, whereas elevated initial CBZ concentrations reduced removal efficiency due to competition for reactive species. Importantly, the CFBC-8/PMS system maintained high degradation efficiency in the presence of common water constituents, including Cl−, HCO3−, NO3−, SO42−, and humic acid (HA), demonstrating strong resistance to matrix interference and good applicability in complex aquatic environments. Electron paramagnetic resonance analysis and radical quenching experiments confirmed that sulfate radicals (SO4·-) were the predominant reactive species responsible for CBZ degradation. Overall, this study demonstrates that integrating magnetic CoFe2O4 nanoparticles with biochar effectively overcomes the intrinsic limitations of pristine biochar, providing a highly efficient and environmentally adaptable catalyst for PMS-based advanced oxidation processes and offering a sustainable route for pharmaceutical wastewater treatment.