Study of modified PVDF membranes with high-capacity adsorption features using Quantum mechanics, Monte Carlo, and Molecular Dynamics Simulations

Abstract

Petrochemical wastewater should be appropriately handled to avoid pollution in natural water. A current research field in this area is to use super hydrophilic membranes with simultaneous superoleophobicity for separating emulsified oil from water. In this study, molecular simulations approaches such as molecular dynamics (MD), Monte Carlo (MC), and quantum mechanics (QM) simulations were used to scrutinize the behavior of adsorption capacities of neat and modified PVDF membranes. For this, PVDF grafted with N-isopropylacrylamide (NIPAAm), azobisisobutyronitrile (AIBN) and also blended with different weight percentages of poly[oligo(ethylene glycol) methacrylate] (PEGMA)-g-1-butyl-3-vinyl imidazolium bromide (BVIm-Br) (PEGMA-co-BVIm-Br) copolymer, as a super hydrophilic agent, to create different membranes compositions. It has been demonstrated in QM simulations that the PVDF-(PEGMA-co-BVIm-Br)-Water-oil configurations facilitate electron transfer more effectively than the other configurations. This makes PVDF-(PEGMA-co-BVIm-Br) a suitable adsorbent for water compared to the neat PVDF. Moreover, the adsorption energy of adsorbates on the membranes with different compositions as adsorbents was estimated using the MC method via Adsorption Locator of Materials Studio (MS) software. Based on the results from the MC simulations, more water molecules were adsorbed into the membrane structure when the hydrophilic agent (PEGMA-co-BVIm-Br) was added to it, which indicates a greater degree of hydrophilicity. Finally, MD simulations were employed to consider the hydrophilic agent effect (PEGMA-co-BVIm-Br) on the physicochemical properties of the membrane structures, such as X-ray diffraction (XRD) pattern, glass transition temperature (Tg), cohesive energy density (CED), fractional free volume (FFV), solubility parameters (δ), and mechanical properties.