Transport of polypropylene, polyvinyl chloride, polyethylene terephthalate and polymethyl methacrylate microplastics in porous media under gradient ionic strength

In this work, column experiments were applied to investigate the transport of four kinds of microplastics (MPs) under a series of ionic strength (IS) conditions. Under 0.1 mM IS, PMMA MPs showed the highest mobility, as well as the PET MPs showed the lowest mobility. With the IS increased, the transport of all kinds of MPs in porous media was generally reduced to the minimum. The transport reducing efficiency of PMMA MPs and PET MPs was lower than that of the PVC MPs and PP MPs. It was found that both the hydro-chemical conditions and basic properties showed combined effect on MPs transport in porous media. The DLVO results were well used to describe the deposition of MPs onto sand surface and excavate the transport behaviors of MPs. The one-site kinetic deposition model was successfully conducted to fit the observed breakthrough curves. Findings from this study elucidated the key factors controlling the MPs transport in porous media, contributing to the prediction and assessment of the environmental risks of MPs.