Coupling adsorption and in-situ Fenton-like oxidation by waste leather-derived materials in continuous flow mode towards sustainable removal of trace antibiotics

• Waste leather derived biochar based adsorptive catalysts (WLBC) were synthesized. • A myriad of • OH can be produced via WLBC mediated Fenton-like reactions. • Recovery of adsorption capability was achieved by degrading surface-enriched SMX. • Coupling adsorption and in-situ oxidation achieves sustainable removal of trace SMX. • SMX degradation pathways were proposed based on LC-QTOF-MS results. The gap of pollutant concentration between simulated sewage (mg/L level) and actual water (μg/L level) strongly limits the application of advanced oxidation processes (AOPs) in natural waters. By coupling adsorption for gathering trace organic contaminants and in-situ catalytic oxidation for recovering adsorption capability, adsorptive catalysts can build a bridge between theoretical research and practical application to promote scientific progress of AOPs. Here, waste leather derived biochar based adsorptive catalysts (WLBC) can effectively adsorb trace sulfamethoxazole (SMX) via electrostatic attraction, hydrophobic interaction, π-π interaction, and Van der Waals forces, moreover, the subsequent in-situ oxidation of surface SMX by hydroxyl radical ( • OH) generated from WLBC mediated Fenton-like reaction will recover the adsorption capability of WLBC. Compared with persulfate-driven AOPs, • OH-dominated oxidation is nonselective for various pollutants and effective for adsorbent regeneration. In addition, the pathway of SMX degradation was proposed based on the results of liquid chromatography-quadrupole time of flight-mass spectrometer (LC-QTOF-MS), involving four stages of 1) nitration, hydroxylation, and hydrolytic reaction of SMX, 2) cleavage of S-N and S-C bonds, 3) ring-opening, 4) mineralization. The adsorption and in-situ Fenton-like oxidation system established by WLBC is capable of efficiently degrading trace pollutants and regenerating adsorbent for long-scale operation, which immunes largely from coexisting substances (e.g. anions, cations, and humic acid) with extremely low metal leaching and relatively low cost. Therefore, this study proposes a strategy for sustainable removal of trace organic pollutant in natural waters based on coupling WLBC induced adsorption and in-situ Fenton-like oxidation.