Osmotic, diffusive and convective volume and solute flows of ionic solutions through a horizontally mounted polymeric membrane.

On the basis of Kedem-Katchalsky's equations in classical and modified versions, the model equations of volume and solute fluxes were presented. In this model the osmotic volume flux is a sum of: simple osmotic, osmotic connected with natural convection and osmotic connected with forced convection fluxes. The solute flux is a sum of: simple diffusion, diffusion connected with natural convection and diffusion connected with forced convection fluxes. On the basis of this model, the respective definitions of the reflection and permeability coefficients were presented. In order to verification of this model, the volume and solute flows in a single-membrane osmotic-diffusive cell, which contains a flat polymer membrane separating water and electrolyte solutions has been studied. In the experimental set-up, water was placed on one side of horizontally mounted membrane. The opposite side of the membrane was exposed to aqueous solution of KCl or NH3. Each experiment was performed for configurations A and B of the single-membrane system. In configuration A water was placed in the compartment above the membrane and solution below it. In configuration B the arrangement of water and solution was reversed. The measurements of stationary volume and solute fluxes were performed in conditions of mechanical stirring and after stopping of mechanical stirring of solutions. On the basis of experimental data of volume and solute fluxes, calculations of reflections and solute permeability coefficients for aqueous solutions of KCl and NH3 were presented.