Appraisal of equations for neutral solute flux across porous sieving membranes

摘要: General transport equations, based on irreversible thermodynamics applied to membranes without regard their structures, are compared with results upon specific membrane models. It is pointed out that the range of validity general linear equations may be extremely small, and attempts extend by thermodynamic considerations have always involved subtle assumptions a nonthermodynamic nature. Simple models used as diagnostic tools pinpoint such assumptions, particular reference often-concealed assumption homoporosity. shown it not possible write an exact equation for solute flux across inert porous only in terms three customary parameters sigma (reflection coefficient), Ps (permeability Lp (hydraulic conductivity), unless strictly homoporous. Even heteroporosity imposes hidden condition delta p greater than pi three-parameter description valid. Useful nonlinear regime require more detailed information structure contained just parameters.