| Separations based on semi-permeable membranes are phenomena of considerable fundamental and applied interest in life and the physical sciences. The most important and technologically demanding application of semi-permeable membranes is reverse osmosis. Reverse osmosis is a general separation technique, in which the objective is to make solvent flow selectively out of a concentrated solution into a less concentrated solution through a semi-permeable membrane. Electro-osmosis refers to osmosis or reverse-osmosis in the presence of an external electric field.; Computer simulation studies have been carried out using a novel technique developed by us to model semi-permeable membranes realistically based on an extension of the NVT molecular dynamics method. In this thesis, both idealized single-layer semi-permeable membranes and zeolite (zk-4) membranes have been studied, Aqueous and methanolic electrolyte solutions have been investigated; the solutes studied include NaCl, LiCl, NaBr and LiBr.; Our study shows that molecular dynamics simulation is an efficient tool to address directly and unambiguously some issues, such as the mass transfer coefficients, the nature of the fluid-membrane interfacial layer, etc. in reverse and electro-osmosis based separations. Our simulations also reveal and explain the rather significant role of solvation forces and the resulting molecular clusters in the separation processes. |
