Adsorption behavior of Cu(II) and Cr(VI) on aged microplastics in antibiotics-heavy metals coexisting system

Recently, the microplastics, as well as the compound pollution of heavy metals and antibiotics, in the aqueous environment have attracted increasing attention, but studies on the behavior of heavy metals on aged microplastics in antibiotics-heavy metals coexisting system are limited. Herein, to explore the impact of antibiotics on the adsorption of heavy metals by aged microplastics, the adsorption behavior of Cu(II) and Cr(VI) on aged polystyrene (PS) and polyvinyl chloride (PVC) were investigated. The results presented that ciprofloxacin (CIP) had negative and positive impacts on the adsorption of Cu(II) and Cr(VI) by aged microplastics, respectively. Moreover, the existence of CIP seemed to have no evident effect on the type of adsorption isotherm model and kinetic model in most adsorption systems of Cu(II). The negative impact of CIP on adsorption of Cu(II) may result from the competition adsorption and high steric hindrance effect, while non-specific interactions between neutral antibiotic-heavy metal complexes and the hydrophobic surface of aged microplastics as well as CIP as bridges influenced positively on adsorption of Cr(VI) on aged microplastics. This work was concerned with the interaction between binary pollutants and aging microplastics to clarify the risks of microplastics in the aqueous environment.