Interfacial interaction between diverse microplastics and tetracycline by adsorption in an aqueous solution

The accumulation of microplastics in offshore aquaculture waters has gradually become a threat to the survival of marine life, and the combined pollution of microplastics and other pollutants is attracting widespread attention. In this paper, tetracycline (TC) was selected as a typical antibiotic, and its adsorption behavior on the surface of diverse type and different sizes of microplastics was studied to explore their combined pollution in an aqueous solution. The results of isotherm fitting showed that the maximum adsorption capacity and coefficient of polyethylene (PE) were the largest, and the adsorption capacity of PE was the strongest among the three microplastics: polyethylene (PE), polystyrene (PS) and polyvinyl chloride (PVC). With increasing PE particle size, the maximum adsorption capacity and adsorption coefficient of TC showed a significant decreasing trend, with a slight fluctuation in the middle. The presence of Pb2+, Cr3+, Cd2+, and Zn2+ markedly enhanced the adsorption of TC to PE, and Cu2+ could reduce the adsorption of TC to PE. The presence of chloride ions did not affect the adsorption process, which indicated that the adsorption mechanism between TC and microplastics is mainly an ion exchange mechanism. These results showed that the surface properties of microplastics and the chemical properties of the aqueous solution played an important role in the adsorption of TC. This study provides important scientific guidance and a theoretical basis for the study of the interfacial behavior, migration and transformation of marine microplastics.