Nonisothermal membrane phenomena across perfluorosulfonic acid-type membranes,Flemion S: Part II. Thermal membrane potential and transported entropy of ions |
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Authors: | K. Hanaoka R. Kiyono M. Tasaka |
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Affiliation: | (1) Department of Materials Science and Engineering, Graduate School of Science and Technology, Shinshu University, 500 Wakasato, 380 Nagano, Japan |
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Abstract: | Thermal membrane potentials across the perfluorosulfonic acid-type membrane, Flemion S, were measured for HCl, alkali metal chlorides, and ammonium and methyl ammonium chlorides. The difference between the mean molar transported entropy of the counterions in the membrane and the partial molar entropy of the counterions in the external solution was determined from the experimental data on thermal membrane potential, thermoosmosis and electroosmosis. The sign of the thermal membrane potential in HCl solution varies from positive to negative with the concentration. In HCl and alkali metal chloride solutions, the order of their thermal membrane potentials (–/T) is H+>Li+=Na+>K+ which is roughly the inverse of that of the crystallographic radii of the ions. However, the order of their entropy differences is H+>Na+>K+>Li+ which is just the inverse of that of their thermoosmotic coefficients (D) or the entropy difference of water in thermoosmosis. For the ammonium and methyl ammonium ion forms, the orders of both –/T and increase with an increasing number of methyl groups: (CH3)4N+>(CH3)3NH+>(CH3)2NH2+> CH3NH3+>NH4+, which is also the inverse of that ofD or. |
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Keywords: | Cation-exchange membrane electroosmosis perfluorosulfonic acid membrane thermal membrane potential transported entropy |
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