Adsorption of some hazardous aromatic hydrocarbons by various pristine and heat-activated aged microplastics as potential pollutant carriers in aquatic environment.

Microplastics (MPs) are ubiquitous in terrestrial and aquatic ecosystems and persistent micropollutants of concern. Their persistence poses risks to ecosystems, human health, and organisms, while they can facilitate the migration and transformation of persistent organic pollutants by acting as vectors for their transportation into the environment and living organisms. This study examined the adsorption/desorption behavior of three nonpolar polycyclic aromatic hydrocarbons (pyrene, anthracene, and fluorene) on pristine and aged MPs, i.e., polystyrene (PS), polyvinyl chloride (PVC), and polymethyl methacrylate (PMMA) through a series of batch adsorption experiments conducted under different pH values, contact times, and salinities. Results indicate that PS adsorbs higher amounts of PAHs than other MPs due to its rough surface, pores, and aromatic configuration strong π-π interactions. The PAHs adsorption followed a pseudo-second-order model, and fit best with the Freundlich isotherm due to multilayer adsorption. Aging with K₂S₂O₈ for 5 days enhanced adsorption on PMMA through surface roughening, reduced sorption on PVC due to oxidation, while PS exhibited minimal impact. The study examined PAHs desorption from MPs in fasted state simulated gastric fluid (FaSSGF), deionized water, and river water. (FaSSGF) showed the highest desorption rates, with pepsin enhancing desorption through micelle formation and weakening π-π interactions,. These findings highlight how organic pollutants are transported by both pristine and aged microplastics, and demonstrate the risk of desorption of these contaminants in aqueous and gastric environments, which may impact on ecosystems and human health.