Sorption of cortisone on polypropylene, polystyrene, and polyethylene microplastics

The ability of microplastics (MPs) to retain organic and inorganic pollutants on their surface is widely demonstrated, acting as vectors for these hazardous species, preconcentrating and carrying them long distances, particularly in the aquatic environments. For this reason, MPs sorption studies are crucial to understand the mechanisms involved in contaminant retention. In this research, the sorption behaviour of cortisone on polypropylene, polystyrene and high-density polyethylene MPs in Milli-Q water and artificial seawater was studied. High-performance liquid chromatography coupled with an ultraviolet detector was used for analyte determination. Kinetic and isotherm studies were carried out through batch sorption experiments under controlled conditions: 1 g of MP pellets, each 3-5 mm in diameter, magnetic agitation at 1000 rpm, and 20 ± 2 °C. Although all types of plastics evaluated in this work showed sorption affinity towards cortisone, retaining between 0.25 to 0.6 µg of cortisone per gram of plastic, changes in sorption capacity and the predominant sorption mechanism were observed when the results obtained in Milli-Q water and artificial seawater were compared.