A mechanistic model of transport processes in porous membranes generated by osmotic and hydrostatic pressure

This work presents a simple molecular model of membrane transport processes generated by hydrostatic (ΔP) and osmotic (ΔΠ) pressure. We postulate that the porous membrane permeability is determined by the size and distribution of its pores. From this postulate and a mechanistic interpretation of the flows we obtain equations for the volume flux Jv, the solute volume flux Jvs, and the solvent volume flux Jvw:Jv=Lp ΔP−Lpσ ΔΠJvs=(1−σ)c̄v̄sLp(ΔΠ+ΔP)Jvw=Jv−(1−σ)c̄v̄sLp(ΔΠ+ΔP)We also observe that the porous membrane properties are described by two phenomenological parameters (Lp and σ), as opposed to three parameters (Lp, σ, and ω) in the standard Kedem–Katchalsky formalism. The extra parameter was eliminated using the correlation relation for the transport parameters found previously and modified in this work. It has a form:ω=(1−σ)c̄Lp