Gravitational effects in the passive osmotic flows across polymeric membrane of electrolytic solutions

Results of experimental study of volume flux in one-membrane system were presented. This system contains horizontal, microporous and symmetrical flat polymeric membrane (Nephrophan), which separate water and electrolyte solution. As binary solutions, aqueous ammonia solutions, which density is lower than water density, were used. As ternary solutions the ammonia with KC1 (0.1 or 0.2 mole.l-1) in aqueous solution were used. The density of ternary solutions was lower, higher or the same as water density. Two configurations of membrane system (A and B) in gravitational field were studied. In configuration A, water was in compartment over the membrane and the solution was under the membrane. In configuration B the succession was reverse. The thermodynamic model of flux graviosmotic effect was elaborated, and the calculations of this effect were performed for A and B configurations of one membrane system. The experimental results are interpreted in terms of gravitational instability that reduces concentration boundary layer dimensions and increases the diffusion permeability coefficient value of the complex: boundary layer/membrane/boundary layer.