Molecular simulation of small molecule adsorption and diffusion behavior in PVA hybrid membranes
The inorganic particle-doped modified polyvinyl alcohol(PVA)membrane materials have promising industrial application prospects in pervaporation dehydration from esterification system.However,it is still lack of mechanism exploration in microscopic view and fundamental theoretical data.In this study,the molecular structure models of two types hybrid PVA materials doped with ZSM-5 and ZIF-67 respectively were constructed using molecular simulation method to elucidate distribution of inorganic particles in PVA chains.The Monte Carlo(MC)method was used to simulate the adsorption behavior of ethyl acetate and water in PVA hybrid materials,and the effects of doping ratio and temperature on adsorption amount and adsorption isotherm were investigated.The diffusion behavior of ethyl acetate and water in the hybrid materials and the fraction of free volume(FFV)within the hybrid materials were simulated by molecular dynamics(MD)method,and the influence of doping ratio and temperature on the diffusion coefficients of small molecules through the hybrid materials were investigated.The results showed that the adsorption of water in the two hybrid materials was significantly higher than that of ethyl acetate,and the adsorption of water in the ZSM-5/PVA was higher than that in ZIF-67/PVA.The diffusion coefficient of water in the two hybrid materials was significantly higher than that of ethyl acetate,and moreover,the diffusion coefficients of small molecules in ZSM-5/PVA were higher than those in ZIF-67/PVA because ZSM-5/PVA has higher FFV.It provides theoretical guidance for the modification of PVA materials and the mechanism of mass transfer separation.
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