[Modification of the Katchalsky's relation between effective and real solute permeability coefficients through...

Using Kedem-Katchalsky equations, in which volume (J(v)) and solute (J(s)) fluxes are functions of the osmotic (delta(pi)) and hydrostatic (deltaP) driving forces, the mathematical model for zeta(s) parameter was elaborated. This parameter describes relation between effective and real solute permeability coefficients through a membrane. Calculations performed on the basis of obtained quadratic equation show that for a polymeric membrane with fixed transport properties parameter zeta(s) is nonlinear function of solution concentration. This nonlinearity is caused by a change of distance between a system and stable state of diffusion. The reason of this nonlinearity is change of distance between a system and stable diffusion state. The appearance of instability related with breaking of symmetry of concentration boundary layers relative to the gravitation direction causes increases of the coefficient value. This is the sign of appearance of diffusion-convection of mass transport.