Chamoulaud Gwenaël, Bélanger Daniel
Département de Chimie, Université du Québec à Montréal, Case Postale 8888, succursale Centre-Ville, Montréal, Québec H3C 3P8, Canada.
J Colloid Interface Sci. 2005 Jan 1;281(1):179-87. doi: 10.1016/j.jcis.2004.08.081.
The ionic transport properties of several cations (H(+), Na(+), and Zn(2+)) across sulfonated ion-exchange membranes modified with an amine were investigated by the measurement of current-voltage curves to determine the effect of the surface modification of the membrane. The membrane was modified by chlorosulfonation and amination with a diamine (N,N-dimethylethylenediamine) and an amine (isoamylamine) to form a sulfonamide bond between amine groups and the surface layer. In the case of the modification with the diamine, the terminal amine was protonated in acidic media or quaternized with methyl iodide. The presence of a positively charged layer on the two sides of the membrane strongly decreased the limiting current flowing across the membrane in the presence of a 1:1 electrolyte such as HCl or HNO(3) due to an increase of the resistance of the membrane. In the case of divalent cations such as Na(+) and Zn(2+), electrostatic repulsion also contributes to the decrease of the limiting current. The presence of divalent anions seems to increase the limiting current somewhat due to their preconcentration within the cationic layer, which facilitates their subsequent transport across the membrane. When only one face of the membrane was modified, the current-voltage measurements showed that the membrane did not behave like a bipolar membrane. For one-side (under forward polarization) and two-side modified membranes, counterions are slightly blocked in the membrane by the cationic layer, which led to a decrease of the membrane conductivity during electrodialysis.
通过测量电流-电压曲线，研究了几种阳离子（H⁺、Na⁺和Zn²⁺）在胺改性的磺化离子交换膜上的离子传输特性，以确定膜表面改性的效果。该膜通过氯磺化和用二胺（N,N-二甲基乙二胺）及胺（异戊胺）胺化进行改性，从而在胺基与表面层之间形成磺酰胺键。在用二胺改性的情况下，末端胺在酸性介质中被质子化或用甲基碘季铵化。在存在1:1电解质（如HCl或HNO₃）的情况下，膜两侧带正电的层会显著降低流过膜的极限电流，这是由于膜电阻增加所致。对于二价阳离子（如Na⁺和Zn²⁺），静电排斥也会导致极限电流降低。二价阴离子的存在似乎会使极限电流有所增加，这是因为它们在阳离子层内发生预浓缩，从而促进了随后穿过膜的传输。当仅对膜的一面进行改性时，电流-电压测量表明该膜的行为不像双极膜。对于单面（正向极化）和双面改性的膜，抗衡离子在膜中会被阳离子层轻微阻挡，这导致电渗析过程中膜的电导率降低。
