Synergistic photocatalysis of BiOCl/MXene activates peroxymonosulfate for enhanced fulvic acid degradation: performance and mechanism insights

Fulvic acid (FA), a key constituent of humic substances, not only contributes to the color of aqueous environments but also leads to the formation of carcinogenic disinfection by-products during chlorination, posing serious ecological and health risks. In this study, a recyclable BiOCl/MXene Schottky junction photocatalyst was successfully synthesized via a conventional hydrothermal method and employed for the photocatalytic activation of Peroxymonosulfate (PMS) to degrade FA efficiently. The BiOCl/MXene composite achieved a high FA removal efficiency of 98.43% within 30 min under visible light. The apparent rate constant (0.1388 min−1) was 3.27 times higher than that of pure BiOCl (0.0425 min−1), revealing a remarkable photocatalysis-PMS synergistic effect (synergy factor = 5.28). The composite maintained excellent performance over a broad pH range (3–9) and at various FA concentrations (20–100 mg L−1), showing strong resistance to ionic interference and outstanding recyclability, with above 80% efficiency retained after five cycles. Characterization and mechanistic studies indicated that the incorporation of MXene significantly increased the specific surface area (41.73 m2 g−1) and improved charge separation efficiency. Trapping experiments and electron paramagnetic resonance (EPR) tests confirmed that h+ and O2•– serve as the dominant reactive species in the degradation process. UV-vis absorption and three-dimensional excitation–emission matrix (3D-EEM) fluorescence spectroscopy revealed the effective disruption of the aromatic structure and chromophores in FA, leading to a total organic carbon (TOC) removal rate of 49.95%. This work provides new mechanistic insights into PMS-assisted stable composite photocatalysts and offers a novel technical strategy for the removal of refractory organic pollutants.