This study investigates the kinetics and reaction mechanisms of the chloride ion ( \({\text{Cl}}^{ - }\) ) removal from sea sand through catalytic ozonation, employing a synthesized manganese oxide-loaded biochar (MnOxBC) catalyst. The MnOxBC was prepared via wet impregnation and characterized by XRD, FTIR, XPS, XRF, and SEM. The catalytic performance was systematically evaluated by varying parameters, including catalyst dosage, ozone dosage, water/sand ratio, and reaction temperature. Under optimal conditions (0.15 g/L catalyst dosage, 25 mg/L ozone dosage, 3:1 water/sand ratio, 50 ℃ temperature, and 15 min reaction time), the chloride removal efficiency (CRE) reached 98.17%, a significant enhancement from 85.75% achieved by water washing alone. Scavenger experiments with tert-butyl alcohol (TBA) and 1,4-benzoquinone (p-BQ) confirmed that the degradation pathway is dominated by hydroxyl radicals (*OH) and superoxide radicals (* \({\text{O}}_{2}^{ - }\) ). XPS analysis revealed a redox cycle between Mn3+ and Mn4+ as the central catalytic mechanism for ozone decomposition into reactive oxygen species (ROS), which subsequently oxidize \({\text{Cl}}^{ - }\) through a multi-step pathway. Kinetic analysis indicated that the reaction followed a pseudo-first-order model, with the catalytic process significantly increasing the apparent rate constant. This work provides fundamental insights into the catalytic ozonation mechanism and kinetics, revealing MnOₓBC as an effective catalyst for chloride oxidation in solid matrices.
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