Catalytic oxidation of clofibric acid by peroxydisulfate activated with wood-based biochar: Effect of biochar pyrolysis temperature, performance and mechanism.

• BC700 can efficiently activate persulfate for clofibric acid (CA) degradation. • C–OH and π-π* transitions in aromatic rings are accounted for radical generation. • Surface-bound reactive radicals are mainly responsible for CA oxidation. • The catalytic activity of reused BC700 was largely recovered by thermal treatment. Wood-based biochars were fabricated at different pyrolysis temperatures of 400–700 °C and used to activate peroxydisulfate (PDS) for the degradation of clofibric acid (CA). Biochar pyrolyzed at 700 °C (BC700) showed more excellent catalytic performance toward CA removal (97.8% in a 60 min reaction) than other BCs. The BC700/PDS process performed efficiently at initial pH range of 4.0–9.0. The effects of PDS concentration and BC700 dosage on CA removal were also examined. Radical quenching experiments and electron paramagnetic resonance (EPR) spectra were applied to identify the reactive radicals generated in the BC700/PDS system. The role of persistent free radicals (PFRs), oxygen functional groups and π-π* transitions in aromatic rings of BC700 for the PDS activation was explored. The reaction intermediates of CA were identified by liquid chromatography–mass spectrometry (LC–MS) and the corresponding degradation pathway was proposed. This study contributes to the development of green materials for sustainable remediation of organic contaminants in water and provides support for further studies. [ABSTRACT FROM AUTHOR]