PVC microplastics as vectors for dye pollutants: Adsorption of rhodamine B and AI-based predictive modeling

Microplastics are persistent pollutants in aquatic ecosystems and can act as carriers of contaminants. Understanding how these particles adsorb and transport contaminants is crucial for assessing their ecological risks. In this study, the adsorption of Rhodamine B (RhB) onto polyvinyl chloride microplastics (PVC-MPs) was evaluated under varying pH, dye concentration, microplastic dosage, and contact time. PVC-MPs exhibited a specific surface area of 0.1713 m2 g−1 and pore volume of 0.0010 cm3 g−1, consistent with a compact structure. Despite this, they achieved a maximum adsorption capacity of 2.09 mg g−1, with higher uptake under acidic conditions. Kinetic analysis showed that the pseudo-first-order model provided the best fit (R2 > 0.980), while equilibrium data were best represented by the Temkin (R2 = 0.967) and Dubinin–Radushkevich (R2 = 0.968) models. The low mean adsorption energy (E = 0.0937 kJ mol−1) confirmed that physisorption dominated the process. FTIR spectra indicated weak interactions such as hydrophobic forces, hydrogen and halogen bonding, and van der Waals forces. Artificial intelligence models showed excellent predictive performance on the test set: ANN achieved R2 = 0.999 and RMSE = 0.0142, while SVR reached R2 = 0.992 and RMSE = 0.0354. Overall, these findings highlight the environmental relevance of PVC-MPs as vectors of synthetic dyes, emphasizing their potential risks to ecosystems and human health and the need for ecotoxicological evaluations.