Vector Transport of Antibiotics By Microplastics in Water

This study investigates the sorption behavior of Ciprofloxacin (CPX) antibiotic, which is a common human and veterinary drug, on polyethylene microplastics (PEMP) through batch sorption experiments. The effects of ionic strength and dissolved organic matter (DOM) were examined by introducing NaNO3 and Humic acid (HA) in to the medium. The sorption of CPX with pH had a gradual increase reaching a maximum sorption at pH 6-7 and then decreased which is likely due to the speciation of CPX at different pH. In the presence of NaNO3, the overall CPX sorption capacity of PEMP decreased as the ionic strength increased revealing that the sorption mechanism was dependent of hydrophobic and electrostatic interactions. Sorption capacity of CPX by PEMP decreased significantly in the presence of HA highlighting the influence of DOM in the aquatic environment towards the CPX sorption and mobilization by PEMP. The spectrum for CPX sorbed PEMP, peaks for C=O, C-F and C-O-C confirmed bound CPX on MP surface. The sorption kinetics model confirmed the parabolic diffusion model and the Elovich model in the presence of HA. The isotherm equilibrium data was well fitted for Hill and Dubinin-Radushkevich models indicating sorption was controlled by pore filling mechanism accompanied by Van der Waals interactions on a heterogeneous surface. Hence, PEMP may act as a potential vector to transport CPX in aquatic environment where the sorption is influenced primarily by the characteristics of the water system and the properties of the adsorbate.