Nonisothermal matter transport in sodium chloride and potassium chloride aqueous solutions. 2. Heterogeneous membrane system (thermodialysis)

Nonisothermal membrane transport has been experimentally studied in the system sodium chloride and potassium chloride aqueous solutions/AP-20 Millipore porous partition. Anomalous behavior is found in both solvent and solute fluxes. The concentration dependence of these fluxes exhibits sharp minima and maxima, respectively. The anomalous regions occur in concentration ranges strongly influenced by the nature of the cation and by (average) temperature. When these results are compiled with the ones relative to thermal diffusion in the same solutions, stringent proof of the close affinity of processes of heat-flux-mediated matter transport in homogeneous and nonhomogeneous (membrane) systems is obtained. The physical cause of the observed anomalies can be tentatively imputed to solute-solvent interactions and to their dependence on solute nature and concentration and on solution temperature. 8 figures, 1 table.