Acta Phys. -Chim. Sin. ›› 2003, Vol. 19 ›› Issue (06): 523-527.doi: 10.3866/PKU.WHXB20030609

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Dielectric Spectroscopy and Its Analysis for the System of Reverse Osmosis Membrane UTC-70 in Aqueous Solution

Li Yu-Hong;Zhao Kong-Shuang;Hikida Takumi   

  1. 1Department of Chemistry,Beijing Normal University,Beijing 100875; Japan Science and Technology Corporation,Kawaguchi,Japan
  • Received:2002-11-28 Revised:2003-01-10 Published:2003-06-15
  • Contact: Zhao Kong-Shuang

Abstract: This paper reported the dielectric properties of the reverse osmosis membrane UTC-70 in NaCl and KCl aqueous solution of different concentrations,studied by dielectric relaxation theory of bilamellar structure.The membrane/aqueous systems had an interfacial polarization behavior that their conductance and capacity displayed a sudden increasing and decreasing in the frequency range of 103~104 Hz.The dielectric parameters of the systems were obtained by nonlinear curve fitting.The relaxation intensity and the characteristic relaxation frequency increasd with the electrolyte concentration supporting the theory of the interfacial polarization.Furthermore,the dielectric characteristics of the systems was analyzed and the phase parameters including the dielectric constant and the conductivity of the membrane were obtained.It was found that the reverse osmosis membrane UTC-70 had a very low density of permanent negative charges.In electrolytes of low concentration the membrane behaved like an ion-exchange membrane.The conductivity ratio of the membrane phase to the aqueous phase first decreased and then approched to a constant as the electrolyte concentration increasesd.This is attributed to the Donnan effect of the permanent charges in the membrane.

Key words: Dielectric spectroscopy, Reverse osmosis membrane UTC-70, Interfacial polarization, Conductivity