SOLVENT TRANSPORT ACROSS CATION-EXCHANGE MEMBRANES UNDER A TEMPERATURE DIFFERENCE AND UNDER AN OSMOTIC-PRESSURE DIFFERENCE

Solvent transport across cation-exchange membranes was measured for water and aqueous salt solutions under a temperature difference and under an osmotic pressure difference. Perfluorosulfonic acid-type membrane Nafion(R) 417, perfluorocarboxylic acid-type membrane Flemion(R) AR1.25, and hydrocarbonsulfonic acid-type membranes Neosepta(R) C66-5T, C66-10F, CM-1 and CM-2 were used. The water flux across cation-exchange membranes in the H+-form is higher than that in other cation forms because the hydrogen ions can exchange with the hydrogen of the adjacent water molecules and thus contribute to the water transport across the membrane as the proton jumps in conductivity. The direction of thermoosmosis across cation-exchange membranes in the Li+-form is from the hot side to the cold side, although in general thermoosmosis across hydrophilic charged membranes occurs towards the hot side.