Synergistic effects and mechanisms of hydroxyl radical-mediated oxidative degradation of sulfamethoxazole by Fe(II)-EDTA catalyzed calcium peroxide: Implications for remediation of antibiotic-contaminated water

•CaO2/Fe(II)-EDTA complex efficiently removed SMX at near neutral pH.•The presence of Cl−, NO3−, SO42− and HA improved SMX degradation.•Unlike to other anions, HCO3− inhibited SMX degradation.•Both HO and O2− contribute to SMX degradation in CaO2/Fe(II)-EDTA system.•Degradation intermediates were identified to propose degradation pathway of SMX.