Dynamic process of UV-aging polystyrene microplastics, simultaneous adsorption of drugs, and subsequently coagulative...

The aging of plastics and their adsorptive interactions with the residual contaminants in water has attracted increasing attentions. In this study, the dynamic process of UV-aging polystyrene (PS) microplastics (MPs) were semi-quantitatively analyzed using a coulter counter, and the adsorptive interactions between the aged PS MPs and two popular drugs[norfloxacin (NOR) and chloroquine phosphate (CQ)] were investigated simultaneously. The MPs presented a rapid size downtrend, reduced from micrometer to nanometer, and the particle number concentration increased about 2 -3 times after a 36.0 h aging effect. The apparent UV-aging process of PS MPs mainly obeyed the pseudo-first order kinetic model in currently measured MPs' size range. The drug uptakes of the aged MPs were fully consistent with the contents of oxygen-containing groups on MPs surface rather than MPs' size. The involved adsorption mechanisms were investigated in detail mainly including electrostatic attraction, hydrogen bonding, and π-π electron donor-acceptor interaction. The drug adsorbed MPs were subsequently efficiently removed by an enhanced coagulation together owing to the synergistic effects of the two pollutants. This study provides a novel and comprehensive perspective on the fundamental understanding the UV-aging process of MPs and the simultaneous adsorption behaviors, furthermore, a strategy was proposed for their collaborative removal.