Porous MnxFe3-xO4 spinel oxides trigger H2O2 activation for boosted degradation of tetracycline: The formation and dominant role of surface-bound radicals

Abstract

Traditional hydrogen peroxide (H2O2)-based advanced oxidation processes (AOPs) are limited by poor catalytic activity, low availability of radicals and severe matrix interference. Herein, a novel porous Mn1.1Fe1.9O4 was successfully synthesized via pores construction-Mn substitution regulation strategy for efficient H2O2 activation and tetracycline removal. The porous Mn1.1Fe1.9O4/H2O2 system achieved a highly efficient removal effect (k = 0.0585 min−1) toward tetracycline (40 mg/L), approximately 14.8 and 16.2 times higher than those of bulk Mn1.1Fe1.9O4 and porous Fe3O4, respectively. Distinct from conventional free radicals-dominated Fenton-like system, the developed surface-bound OH-dominated porous Mn1.1Fe1.9O4/H2O2 system could degrade the contaminants that adsorbed onto Mn1.1Fe1.9O4 surface, and displayed broad pH adaptability (3.0–9.0) and high anti-interference to inorganic ions, humic acid, and even real water matrixes. The density functional theory (DFT) calculations confirmed that dual Mn − Fe sites could co-adsorb H2O2 through a “bridge” mode to induce the in-situ generation of surface-bound OH, and Mn was the main active sites. Besides, the tailored porous structure offered a rapid mass transfer channel for continuously generating surface-bound OH and enhancing H2O2 utilization efficiency by shorting migration distance between active species and H2O2/pollutant. This work provided novel insights for the in-situ generation of surface-bound OH and the development of H2O2-based AOPs with fine anti-interference property.