Molecular Design Of Membrane Materials For Alcohol And Water Separation

The key foundation of membrane separation technology is the membrane material.The permselectivity of pervaporation and gas separation process were decided by thedissolve-diffusion behavior of small molecule in the polymer. In recent years, the molecularsimulation had been applied to predict the thermodynamics and dynamics of smallmolecules in the membrane. The purpose of this paper was to design the membranematerial based on the literature reported. The designed material can be used to separate thelow consistency ethanol and aqueous solution. It had a better permselectivity of ethanol andwater molecules. In this paper, the moleculer simulation method was used to calculation themembrane material. The experiment time can be saved and the blindness can be avoided inthe experiment process. Also a strong theoretical basis can be provided by it.In this paper, the software of Material Studio was used to design and calculate themembrane material6FDA/oODMS. The diffusion coefficient and solubility coefficientwere calculated under three different temperature (318K,328K,338K). First of all, theMaterial Studio was used to build the unit of PDMS and6FDA/8m, the diffusion of O2inthe PDMS and the solubility of CO2in the6FDA/8m were calculated. The method wasdemonstrated correctly. Then, the unit of6FDA/oODMS was builded by using MS. Thesolubility and diffusion were calculated under different temperature based on the MD.By comparison and analysis, it was found that the permeability coefficient of ethanolincreased with the fragment of ODMS increased in the separation membrane. The reason ofthis phenomenon was that the molecular chain increased as the fragment of ODMSincreased, and the free volume of the system increased. The result was that the membranewas in favor of the ethanol molecule to pass. According to the result, it was found that thediffusion of ethanol and aqueous in the membrane were influenced with each other. It canbe found that under the same temperature, ethanol molecule always had the bestpermeability coefficient and aqueous molecule always had the small permeabilitycoefficient in the6FDA/6ODMS, so the membrane6FDA/6ODMS had the bestpermselectivity and the membrane6FDA/6ODMS was the best material for separation ateach temperature. Compared the results under different temperature, it was found that ethanol molecule had the biggest permeability coefficient and aqueous molecule had thesmallest permeability coefficient in the6FDA/6ODMS under318K. Finally, it was foundthat at318K the6FDA/6ODMS membrane had the best solution to design the membrane.