Harnessing the radical potential of calcium-activated biochar for non-peroxide catalytic degradation of bisphenol S

[Display omitted] •Capturing the strong oxidizing organic radical signals generated by O2/BC system.•Boost in Biochar Catalysis through Alkali Metals.•Unveiling Non-Peroxide Oxidation with Calcium-Activated Biochar.•Proven Efficacy in Persistent Organic Pollutant, BPS, Degradation.•BPS Degradation Pathway Elucidation Through DFT Calculation. Biochar, characterized by its rich surface functional groups, defective structure, and inherent aromaticity, serves as a promising catalyst in Advanced Oxidation Processes (AOPs). The generation of Reactive Oxygen Species (ROS) stems from the heterolytic cleavage of peroxides, facilitated by electron transfer from biochar's functional groups. However, safety hazards of peroxides during transportation and storage persist. This study explores a non-peroxide-based oxidation mechanism via Calcium Chloride-activated biochar (CaBC). Remarkably, upon aeration, Bisphenol S (BPS) concentration in water decreased by 25.7 % after reaching adsorption saturation. Reactive Oxygen Species (ROS) generation was confirmed by electron paramagnetic resonance, with species including •OH, •O2–, •CH3, •CH2OH, and CH3C(=O)OO•. Degradation products of BPS were identified using Liquid Chromatography-Mass Spectrometry (LC-MS), their biosafety was assessed, and the degradation pathways of BPS were analyzed through density functional theory (DFT) calculations. This study highlights the potential of biochar in safer, mild catalytic oxidation processes and offers insights into the radical reactions of carbon-based materials in aqueous environments.