Efficient degradation of methyl orange in water via both radical and non-radical pathways using Fe-Co bimetal-doped MCM-41 as peroxymonosulfate activator

Abstract

Cobalt-mediated activation of peroxymonosulfate (PMS) has been widely investigated for the effective oxidation of organic contaminants in wastewater. Herein, monometal- and bimetal-doped MCM-41 catalysts (Fe-MCM-41, Co-MCM-41, and FeCo-MCM-41) were synthesized by using one-pot hydrothermal method and attempted to degrade artificial methyl orange (MO) dye wastewater via PMS activation. The influences of initial PMS concentration, pH, catalyst dosage and reaction temperature on the degradation efficiency of MO were systematically examined. Compared with the contrasting catalysts, FeCo-MCM-41 exhibited extremely higher activity and lower amount of metal leaching in the degradation process. The excellent catalytic activity of FeCo-MCM-41 was ascribed to the high dispersion of metals and the synergistic effects of Co2+/Co3+ and Fe2+/Fe3+ redox cycles. A series of radical inhibition and electron paramagnetic resonance experiments revealed that both radical and non-radical pathways were involved in the degradation of MO. Singlet oxygen (1O2) was unveiled to be the dominant reactive oxygen species in the FeCo-MCM-41/PMS system. The possible degradation pathways were proposed based on the identification of intermediate products generated in the degradation process by LC-MS analyses.