DETERMINATION OF SOME TRANSPORT-COEFFICIENTS FOR THE SKIN AND POROUS LAYER OF A COMPOSITE MEMBRANE

Retention curves, membrane potential, diffusion and electrical resistance for two membranes: a composite membrane (HR 95) and the support membrane (without the skin layer), have been measured for different solutions of NaCl and MgCl2. Salt permeabilities in the skin and porous layers of the composite membrane were calculated and these latter values were compared with those obtained with the porous polysulfone membrane by diffusion experiments. From the experiments it was concluded that 92% of the total flux-resistance was due to the selective skin layer, whereas only 78% of the total diffusion resistance under dialysis conditions was due to the skin layer. A comparison of the experimental and calculated values for the electrical resistance of the polysulfone membrane has also been made. In both cases, good agreements were found. Cation transport numbers in the skin and porous layers of the composite membrane have also been obtained.