Modulating oxidative capacity to simultaneously enhance microplastics aging and reduce adsorption performance: A novel approach to environmental remediation

During the conventional aging process of microplastics, a significant amount of oxygen-containing functional groups are generated, which enhances the adsorption capacity of aged microplastics. In this study, we constructed various electron beam/strong oxidant systems and adjusted the oxidative capacity to enhance the aging performance of polypropylene while reducing its adsorption ability. Experimental results indicate that as the oxidative capacity of the system increases, the aging degree of polypropylene significantly improves, yet the adsorption performance for sulfonamides exhibits a trend of initially decreasing and then increasing. Conventional methods typically generate a large number of oxygen-containing functional groups on the surface of microplastics. These oxygen-containing functional groups enhance the adsorption capacity for sulfonamide pollutants through electrostatic interactions, hydrogen bonding, and van der Waals forces. As we further enhance the oxidative capacity of the system, reactive free radicals continue to attack the surface oxygen-containing functional groups, resulting in their removal and transformation. We determined for the first time the changes in the aging process of microplastics and the surface oxygen-containing functional groups under different oxidative capacities. This breakthrough reveals the nonlinear relationship between oxidation intensity and the evolution of surface functional groups. At low oxidation intensities, reactive radicals preferentially attack and remove oxygen-containing functional groups, thereby decreasing the sites for pollutant adsorption. In contrast, at high oxidation intensities, the restructuring of functional group structures facilitates a rebound in adsorption performance. This mechanism systematically clarifies the longstanding "aging-adsorption" vicious cycle, providing theoretical support for the precise regulation of microplastic aging pathways.