Enhanced the interaction of biodegradable microplastics with tetracycline by persulfate oxidation process

The interaction of biodegradable microplastics with pollutants has raised widespread public attention recently. However, investigation on the interaction under oxidation process is limited. In this study, the interaction process of polyhydroxyalkanoates microplastics (PHA-MPs) with tetracycline (TC) under persulfate-based oxidation systems was investigated. Characterization results indicated that persulfate oxidation process not only changed the surface morphology of PHA-MPs, but also produced many oxygen-containing functional groups. Meanwhile, through the application of 2D-COS analysis, the oxidation sequence of functional groups in PHA-MPs was clearly identified. The adsorption capacity of PHA-MPs was maximized at pH = 7, and high salinity inhibited the adsorption capacity, while the addition of Co(II), Ni(II), and Cu(II) could significantly promote the adsorption capacity. In addition, the adsorption kinetics fitted well with the pseudo-second-order kinetic model, and the adsorption isothermal process followed the Freundlich model, which was belonging to multi-layer adsorption. The above results were helpful to further assess the risks associated with the combined pollution of biodegradable MPs and organic pollutants.