Final Report: Computer Simulation of Osmosis and Reverse Osmosis in Structured Membranes

Sohail Murad

关键词: ACCURACY;    ADSORPTION;    CARBON DIOXIDE;    CHEMICAL SHIFT;    COMPUTERIZED SIMULATION;    DESALINATION;    DIFFUSION;    GASES;    ION EXCHANGE;    MEMBRANES;    MIXTURES;    NITROGEN;    OSMOSIS;    PURE STATES;    SEPARATION PROCESSES;    SIMULATION;    WATER Molecular Modeling;    Reverse Osmosis;    Gas Separation;    Water Treatment;    Pervaporation.;   

DOI  :  10.2172/1032490
RP-ID  :  FINAL REPORT
PID  :  OSTI ID: 1032490
Others  :  TRN: US201218%%968

美国|英语

来源: SciTech Connect

【 摘 要 】

Molecular simulation methods were developed as part of this project to increase our fundamental understanding of membrane based separation systems. Our simulations clarified for example that steric (size) effects had a significant impact on the desalination membranes. Previously it was thought the separation was entirely driven by coulombic force (attractive/repulsive forces at the membrane surfaces). Steric effects played an important role, because salt ions in brackish water are never present alone, but are strongly hydrated which effectively increases their size, and makes it impossible to enter a membrane, while the smaller water molecules can enter more readily. Membrane surface effects did play a role in increasing the flux of water, but not in the separation itself. In addition we also developed simulation methods to study ion exchange, gas separations, and pervaporation. The methods developed were used to once again increase our fundamental understanding of these separation processes. For example our studies showed that when the separation factor of gases in membranes can be significantly affected by the presence of another gas, it is generally because the separation mechanism has changed. For example in the case of nitrogen and carbon dioxide, in their pure state the separation factor is determined by diffusion, while in mixtures it is influenced more by adsorption in the membrane (zeolite in our case) Finally we developed a new technique using the NMR chemical shift to determine intermolecular interactions for mixtures. For polar-nonpolar systems such as Xe dissolved in water we were able to significantly improve the accuracy of gas solubilities, which are very sensitive to the cross interaction between water and Xe.