Microplaastics as potential bisphenol carriers: role of adsorbents, adsorbates, and environmental factors

Microplastics (MPs) are widely found in the environment and can act as carriers for various toxic substances, promoting their diffusion and bioenrichment. Accordingly, it is necessary to investigate the transfer of MPs between the environment and organisms. This study investigated the adsorption potential of four types of MPs, namely polystyrene (PS), polypropylene (PP), polyamide (PA), and polyvinyl chloride (PVC), for bisphenol (BP) A, B, F, and S (BPA, BPB, BPF, and BPS, respectively). The results showed that all four types of MP could act as environmental carriers of BP. PA had the highest BPA adsorption capability, with a value of 109.0 ± 39.93 μg·g^-1, followed by PS (89.24 ± 26.12 μg·g^-1), PVC (53.08 ± 15.32 μg·g^-1), and PP (41.83 ± 11.51 μg·g^-1).Thepolymer type, SSA, and surface functional groups were the main factors affecting the BP adsorption capacity of MPs. The concentration, hydrophobicity, and dissociation ability of BPs also substantially affected their adsorption behavior. The adsorption efficiency of different BPs on the same MPs ranged from 37.4 ± 3.7% to 59.1 ± 2.8%. The adsorption capacity of BPs on MPs decreased with increasing temperature. Salt ions in the solution significantly enhanced BP partitioning in the solid phase owing to the salting-out effect. Additionally, the adsorption of BPs on MPs was pH dependent. Higher pH values increased electrostatic repulsion, which decreased the adsorption capacity. These results demonstrate that MPs can serve as BP carriers in the environment and their potential BP loads might be considerably greater than that of BP additives used during plastic production.