a Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Málaga, E-29071 Málaga Spain
b Chemical Engineering Department, Technical University of Denmark, DK-2800 Lyngby Denmark
Abstract:
Retention curves with a composite membrane (HR 95) have been measured for different solutions of Na2SO4 and MgSO4. Salt permeabilities in the skin and the porous layer of the composite membrane have been calculated. The results show that the salt permeability in the skin layer is 15% of that corresponding to the porous layer. Electrical resistances for the composite membrane and another membrane similar to the supported membrane (without skin layer) have been measured using both direct and alternating current. From the a.c. values, assuming that no concentration polarization exists at the skin-porous layer interface, the electrical resistance for the skin layer at different concentrations was estimated. The membrane resistance values were also determined by impedance spectroscopy measurements, and the results agree with those previously found by a.c. measurements.