Oxygen vacancies mediate the degradation of refractory organics in the interflow around a simple landfill: Based on Mg-Fe3O4/PMS system

Abstract

The interflow around simple landfills in villages and towns contains high-risk and trace refractory organics (TRO), which can have serious effects on the rural living environment. Here, an iron-based catalyst containing oxygen vacancies was prepared by doping with Mg, and the Mg-Fe3O4/peroxymonosulfate (PMS) advanced oxidation system was constructed to mediate the efficient degradation of the pollutants in the interflow around simple landfills. The parameters of the system were optimized to maximize the degradation of the pollutants in interflow via single-factor and response surface experiments. Electron paramagnetic resonance revealed that oxygen vacancies can effectively form in the catalyst by doping co-precipitation. The rate of chemical oxygen demand removal from the interflow was 96.01 ± 1.12% under the following conditions: 10% Mg doping, 1.03 g·L−1 catalyst dosage, and 13.47 mmol·L−1 PMS dosage. UV254 and E280 decreased from 0.403 and 0.305 cm−1 to 0.199 and 0.164 cm−1, respectively, and E300/E400 increased from 5.56 to 8.92 after the reaction. Excitation–emission matrix spectra showed that the corresponding absorption peaks of fulvic acid and tyrosine analogs were heavily attenuated. Gas chromatography–mass spectrometry analysis showed that the number of TRO decreased from 57 to 9, indicating that a large amount of TRO had been removed. A mechanistic analysis revealed that SO4·- and OH· might play a major role in the reaction process and that 1O2 plays an important role in the degradation process.