Interactions of pristine and aged nanoplastics with heavy metals: Enhanced adsorption and transport in saturated porous media

Abstract

Interactions of nanoplastics (NPs) with other contaminants are attracting attention, and it is essential to investigate the interaction of aged plastics with heavy metals. We obtained aged nanopolystyrene by UV radiation and investigated the effects of aged NPs on the adsorption and cotransport of Pb-(II) and Cd-(II). The results showed that the UV-aged NPs led to the enhanced adsorption capacity of heavy metals due to the increase in oxygen-containing functional groups, and the promotion of transport by the aged NPs to heavy metals was stronger than that of the pristine NPs. Furthermore, the heavy metals retained in the columns could be freed by the NPs, and the aged NPs were more capable of freed of heavy metals as carriers. In conclusion, the radiation of NPs is correlated with their ability to promote heavy metal transport, and the oxygen content on the surface of NPs plays an essential role in this process to promote the transport of heavy metals in porous media. The ADR equation and DLVO theory simulates the transport behaviour of NPs well. This study is expected to provide a new perspective for assessing the potential risk of aged NPs in soil-groundwater systems.

Keywords: Adsorption; Facilitated transport; Heavy metals; Nanoplastics.