Activation of peroxymonosulfate by metal oxide nanoparticles for mitigating organic membrane fouling in surface water treatment

Abstract

Recent work has demonstrated the feasibility of peroxymonosulfate (PMS) activated by metal oxide (MeOx) nanoparticles for organic micropollutants removal, whereas little is known about its performance on membrane fouling control. In this work, PMS oxidation activated by typical MeOx nanoparticles (i.e., MnO2, CuO and Co3O4) were proposed for reducing organic membrane fouling in surface water treatment. The results showed that PMS alone and MnO2/PMS were only effective for alleviating reversible fouling, whereas the mitigation effect for irreversible fouling was relatively limited. By contrast, CuO/PMS and Co3O4/PMS dramatically alleviated both reversible and irreversible fouling. To identify the organic composition in surface water, fluorescence excitation-emission matrix coupled with parallel factor and molecular weight distribution analyses were conducted. MeOx/PMS oxidation decreased each fluorescent component to varying degrees, and also converted macromolecular organics into low molecular weight substances. The oxidation ability of MeOx/PMS was affected by the type of MeOx, which followed the order: Co3O4 > CuO > MnO2. The effect of natural organic matter fraction on fouling control was further studied with humic acid, bovine serum albumin, and sodium alginate. The effectiveness of Co3O4/PMS in alleviating membrane fouling by multiple pollutants was further verified via scanning electron microscope and Fourier transform infrared spectrometer. The presence of MeOx nanoparticles significantly accelerated the consumption of PMS, and the generation of both •OH and SO4•− radicals was confirmed by electron paramagnetic resonance spectroscopy and radical quenching tests. The model fitting results suggested that the conversion of fouling mechanism from pore blocking to cake filtration was delayed to varying degrees by MeOx/PMS. The results suggest that MeOx/PMS oxidation has the potential for membrane fouling control in practical applications.