Heterogeneous catalytic activation of peroxymonosulfate for efficient degradation of organic pollutants by magnetic Cu0/Fe3O4 submicron composites

Abstract

Magnetic Cu0/Fe3O4 submicron composites were prepared using a hydrothermal method and used as heterogeneous catalysts for the activation of peroxymonosulfate (PMS) and the degradation of organic pollutants. The as-prepared magnetic Cu0/Fe3O4 submicron composites were composed of Cu0 and Fe3O4 crystals and had an average size of approximately 220 nm. The Cu0/Fe3O4 composites could efficiently catalyze the activation of PMS to generate singlet oxygen, and thus induced the rapid degradation of rhodamine B, methylene blue, orange II, phenol and 4-chlorophenol. The use of 0.1 g/L of the Cu0/Fe3O4 composites induced the complete removal of rhodamine B (20 μmol/L) in 15 min, methylene blue (20 μmol/L) in 5 min, orange II (20 μmol/L) in 10 min, phenol (0.1 mmol/L) in 30 min and 4-chlorophenol (0.1 mmol/L) in 15 min with an initial pH value of 7.0 and a PMS concentration of 0.5 mmol/L. The total organic carbon (TOC) removal higher than 85% for all of these five pollutants was obtained in 30 min when the PMS concentration was 2.5 mmol/L. The rate of degradation was considerably higher than that obtained with Cu0 or Fe3O4 particles alone. The enhanced catalytic activity of the Cu0/Fe3O4 composites in the activation of PMS was attributed to the synergistic effect of the Cu0 and Fe3O4 crystals in the composites. Singlet oxygen was identified as the primary reactive oxygen species responsible for pollutant degradation by electron spin resonance and radical quenching experiments. A possible mechanism for the activation of PMS by Cu0/Fe3O4 composites is proposed as electron transfer from the organic pollutants to PMS induces the activation of PMS to generate 1O2, which induces the degradation of the organic pollutants. As a magnetic catalyst, the Cu0/Fe3O4 composites were easily recovered by magnetic separation, and exhibited excellent stability over five successive degradation cycles. The present study provides a facile and green heterogeneous catalysis method for the oxidative removal of organic pollutants.