Adsorption of Copper Ions to Secondary Microplastics in Seawater

One of the main sources of secondary microplastics (MPs) in the marine environment is single-use plastic products. However, research on their adsorption capabilities is still limited. In this study, we used a representative set of well-characterized micro-sized fragments, films, and foam to evaluate differences in copper(II) adsorption via a series of batch adsorption experiments. We aimed to understand how the adsorption capacity of Cu(II) differs between a set of secondary MPs in model seawater. We examined the effect of particle size, surface hydrophobicity, and salinity as factors influencing adsorption. The highest adsorption capacity was observed for foam fragments made from a clamshell PS food container followed by a food tray made from PP (591 ± 168 and 353 ± 45 µg/g of MP, respectively). The presence of a higher salinity environment had no negative effect on the adsorption capacity, except that of spherical PS. Our results suggest that the chosen MPs (hard fragments and films) do not have a high ability for Cu(II) adsorption, except for expanded PS and PP films. This study also highlights the difficulties associated with using irregular pieces of post-consumer plastic in model experiments.