Efficient purification of tetracycline over ZIF-8-encapsulated Mn2O3 via persulfate activation: Pivotal roles of heterostructure and surface Mn(II)

Advanced oxidation processes (AOPs) based on persulfate (PS) activation is an extremely effective method to removal antibiotics in wastewater. In this process, endowing abundant active sites and rapid electron transfer channel over catalyst are two essential factors for high performance towards decontamination. Herein, a novel core-shell catalyst Mn2O3@ZIF-8 with large specific surface area was prepared to remove antibiotics via PS activation under visible light irradiation. Intriguingly, the removal efficiency of tetracycline (TC) by Mn2O3@- ZIF-8 with optimal compound ratio was 3.2 times that of original Mn2O3. The characterizations and density functional theory calculations proved that a Zn -O -Mn electron transfer channel was constructed in Mn2O3@ZIF-8 heterostructure, which greatly promoted electron transport and photogenerated electron-hole separation. In addition, the activation of PS and degradation of pollutants by Mn2O3@ZIF-8 was a highly surface-dependent reaction. The correlation between surface physicochemical properties and pollutant removal was further established to uncover the dominant active sites for PS activation. The quenching experiments and electron paramagnetic resonance (EPR) tests confirmed that PS was mainly activated by surface active MnII(s) and dissociated into reactive oxygen species center dot OH, O2 center dot-, and 1O2, or formed reactive complexes MnII(s)-S2Oa-* to induce electron transfer and achieve TC oxidation. Besides, Mn2O3@ZIF-8 exhibited satisfactory removal of multiple pollutants and actual pharmaceutical wastewater as well as effective detoxification due to the coexistence of the above radicals and non-radicals pathways. The study provides novel insights into the design of high efficiency of Mn-based catalysts for antibiotic wastewater purification.