反渗透膜UTC-70在水溶液中的介电谱及其解析

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

根据平面层状体系介电弛豫理论研究了反渗透膜UTC-70在各种浓度氯化钠和氯化钾溶液中的介电弛豫行为.利用计算机拟合的方法得到膜/溶液体系的介电参数,并由此计算得到了UTC-70膜相和水溶液相的相参数,获得了反映反渗透膜UTC-70荷电情况的信息及其与电解质溶液浓度的关系,介电解析的结果解释了介电弛豫的产生机制.

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 10(3)similar to10(4) 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.