Ofloxacin degradation in water and porous media: Synergy effects via hydrogen peroxide activation by a micro electrolytic iron-carbon composite

[Display omitted] •Ofloxacin (OFL) is efficiently removed by nZVI@PAC/H2O2 heterogeneous system.•The PFRs on the surface of nZVI@PAC promoted the activation of H2O2.•The electron regulation of Fe on PAC surface enhanced the activity of nZVI@PAC.•First complete degradation pathway of OFL in a nZVI@PAC/H2O2 system is provided.••OH and FeIVO are the main reactive species in the nZVI@PAC/H2O2 system. Ofloxacin (OFL) may cause potential ecological risks since it cannot be effectively removed by conventional biological degradation. The advanced oxidation process is an efficient approach for antibiotic removal. Herein, a heterogeneous system for hydrogen peroxide (H2O2) activation by nanoscale zero-valent iron (nZVI) supported on powdered activated carbon (PAC) composite (nZVI@PAC) was proposed to proceed with the removal of OFL. Typically, OFL (25 mg/L) can be removed up to 94.7 % within 60 min ([H2O2] = 10 mM, [nZVI@PAC] = 125 mg/L, pH = 6, T = 318 K). The effects of initial OFL concentration, pH, nZVI@PAC dosage, H2O2 concentration, and different actual water matrices were examined to explore the application conditions and resistance of the nZVI@PAC/H2O2 system. Meanwhile, the quenching experiment, PMSO probe experiment, and EPR results showed •OH and FeIVO were the dominant reactive species in the system. Moreover, a sensible mechanism for OFL removal was proposed that nZVI@PAC aggregates OFL on its surface by adsorption, and then persistent free radicals (PFRs) and nZVI on the PAC degrade OFL by activating H2O2 to produce •OH and FeIVO. Furthermore, the effect of micro-electronic iron-carbon composite was proved by electrochemical experiments and density functional theory (DFT) calculations. Moreover, the degradation pathway of OFL in the nZVI@PAC/H2O2 system and the toxicity assessment of intermediates were also given. Meanwhile, sequential runs and continuous flow column experiments showed nZVI@PAC/H2O2 system had high stability. This work provides an innovative strategy of an advanced oxidation process based on heterogeneous reactions for organic contaminants removal using metal–carbon catalysts.