Surface deoxygenation via electron beam/oxidant treatment: A novel pathway to reduce pollutant adsorption on aged microplastics

Several methods have been developed to age microplastics (MPs), and aged microplastics also exhibit a significant increase in adsorption capacity for pollutants. We utilized electron beam/oxidant to create strong oxidative environment, achieving efficient aging degradation of microplastics and significant reduction in aged microplastics adsorption capacity. The adsorption capacity of aged polyethylene decreases from 1.29 mg g to 0.76 mg g with Electron beam/Hydrogen peroxide system, and to 0.98 mg g with Electron beam/Potassium persulfate system. With the increasing oxidizing ability, the total organic carbon concentration of the aged microplastics increased from 14.6 mg L to 23.8 mg L, and the carbonyl index value decreased from 0.69 to 0.19, O/C from 0.151 to 0.138. The addition of strong oxidants promotes the further conversion of carbonyl to hydroxyl on the aged PE surface, ultimately achieving the removal of oxygen-containing functional groups. We have first revealed a more in-depth aging process of polyethylene under strong oxidative conditions, which involves oxidation and deoxygenation processes. The removal of oxygen-containing functional groups reduces the adsorption capacity of polyethylene, lowering the environmental hazards. This study introduces a novel method to enhance the degradation of aged polyethylene and reduce adsorption equilibrium capacity.