Membrane Phenomena in Nonisothermal Systems: Part 3. Thermal Membrane Potential across Various Hydrophobic Anion-Exchange Membranes with 10 and 14% Divinylbenzene

摘要

The thermal membrane potential across anion-exchange membranes having various hydrophobic anion-exchange groups was measured for various electrolyte solutions. A good linear relationship between the thermal membrane potential (△ψ) and the logarithmic temperature difference (△ln T) was observed. The temperature coefficient of the thermal membrane potential (△ψ/△ln T) was found to be a function of the logarithmic activities of ions with a slope of RT~c/F for 1-1 electrolytes and RT~c/(2F) for 1-2 electrolytes, where T~c is the constant temperature of the solution on one side of the membrane. The absolute value of △ψ/△ln T decreased with increasing the molality of the external electrolyte solutions. The absolute value of △ψ/△ln T in KCl solutions was higher than that in KIO_3 solutions. For halide ions the order of the absolute values of the thermal membrane potential (△ψ) was Cl~- > Br~- > I~-, which corresponds to the order of the values of the B-coefficient in the Jones-Dole expression for the viscosity of the solutions, but opposite to that of the conventional partial molar volume. For large oxoanions the order of the absolute values of △ψ was found to be NO_3~- > IO_3~- > SO_4~(2-), which is opposite to the order of the B-coefficient as well as to that of the molar volume of these hydrated ions.