Transport of emerging organic ultraviolet (UV) filters in ceramic membranes: Role of polyethylene (PE) microplastics

Microplastics can be considered potential carriers of emerging organic ultraviolet (UV) filters due to their considerable adsorption capacity in wastewater treatment. The adsorption behavior of organic UV filters, which are commonly contained in personal care products to preserve the skin against UV radiation, onto polyethylene (PE) microplastics were systematically studied to investigate their combined effects. Kinetics and isotherm analyses revealed that the adsorption of four organic UV filters onto PE microplastic surfaces followed a multi-rate and a heterogeneous multi-layer pattern. Several factors including salinity, microplastic size, and dosage also influenced the adsorption efficiency due to hydrophobic interactions. A bench-scale cross-flow ceramic membrane filtration experiment was investigated to evaluate the role of PE microplastics on the retention performance of organic UV filters. The retentions for organic UV filters were 34.2%-37.8% in the non-existence of PE microplastics. Conversely, organic UV filter retentions were significantly increased up to 82.2%-97.9% when they were adsorbed onto the PE microplastics, which were almost completely retained by the ceramic membrane. Therefore, organic UV filters can likely migrate and eventually be carried by PE microplastics, thus increasing the retention of both emerging organic UV filters and microplastics prior to discharge from wastewater treatment facilities.