Mechanistic insights into PVC microplastic adsorption on montmorillonite: A first-principles approach toward...

Plastic pollution has emerged as a pervasive environmental threat, with polyvinyl chloride (PVC) being a persistent polymer that can degrade into smaller fragments. These particles contaminate aquatic environments, accumulate in biota, and pose serious ecological and health risks. This study used computational methods to investigate the adsorption of vinyl chloride (VC), a PVC oligomer, onto montmorillonite (MMT). Vienna Ab initio Simulation Package was used to perform Density Functional Theory calculations. The interaction between VC and MMT was assessed through binding energy, density of states (DOS), projected DOS, and charge analysis. A negative binding energy (- 0.62 eV) confirmed favorable adsorption. The reduced HOMO-LUMO gap in the VC-MMT hybrid indicated electronic interactions. The orbital-resolved projected density of states (PDOS) showed overlap between the O 2p orbitals of MMT and the H 1 s orbitals of VC. Bader charge analysis revealed negligible charge transfer to the VC molecule upon adsorption, while charge density difference showed localized electron redistribution at the VC-MMT interface. These results indicate a noncovalent interaction without the formation of shared charge density, consistent with polarization-driven physisorption. Molecular dynamics simulations supported these interactions, showing that the VC molecule remained associated with the MMT surface through noncovalent forces. Root mean square deviation (RMSD) confirmed that the VC-MMT structure remained stable throughout the simulation, while the interaction energy exhibited stable fluctuations over time. These findings suggest that MMT holds potential as an effective sink for PVC microplastics through stable, non-covalent surface retention, thereby reducing their dispersion in environmental matrices.