Determination of the pKa of poly (4-vinylpyridine)-based weak anion exchange membranes for the investigation of the side proton leakage
Determination of the pKa of poly (4-vinylpyridine)-based weak anion exchange membranes for the investigation of the side proton leakage
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DOI：
10.1016/j.memsci.2008.10.054
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发表时间：
2009-01-20
影响因子：
9.5
通讯作者：
Huguet, Patrice
中科院分区：
文献类型：
--
作者：
Franck-Lacaze, Ludivine;Sistat, Philippe;Huguet, Patrice
本文对阴离子膜进行了物理化学研究，以期更好地了解酸性溶液处理中的质子泄漏现象。感兴趣的膜由接枝在两种不同共聚结构上的聚(4-乙烯基吡啶)可电离基团组成。用共聚焦拉曼显微镜测定了这两种膜的酸性常数，这取决于平衡酸性溶液的pH值和所测试的酸的性质。此外，膜的电导率和水含量仅以质子化形式显示：所得数值可与可电离基团的pK(A)相关联。对膜与酸性溶液平衡时的化学组成的计算表明，膜内的水相比外平衡溶液的酸性小得多，导致膜内的酸度常数(pK(A))大于棒(真)，另一个与溶液相有关(pK(A)(表观))。这一基础工作导致了要处理的酸性溶液的浓度范围：酸性溶液的pH必须是膜的表观pK(A)的数量级，以使活性聚(4-乙烯基吡啶)基团的含量和离子通过膜的高选择性传输。(C)2008爱思唯尔B.V.保留所有权利。
The paper deals with physicochemical investigations of anionic membranes in view to better understanding the proton leakage phenomenon in the treatment of acidic solutions. The membranes of interest consisted of poly (4-vinylpyridine) ionisable groups grafted on two different copolymer structures. The acidity constant of the two membranes has been determined by confocal Raman microscopy, depending on the pH of the equilibrating acidic solutions, and the nature of the acid tested. In addition the membranes were shown to exhibit an appreciable electrical conductivity and water content only in the protonated form: the values obtained can be correlated with the pK(a) of the ionisable groups. Calculations of the chemical composition of the membrane in equilibrium with the acidic solutions revealed that the aqueous phase inside the membrane is far less acidic than the external equilibrating solution, leading to the acidity constants in the membrane ((pK(a)) over bar (true)) and another related to the solution phase (pK(a)(apparent)). This fundamental work led to the concentration range of the acidic solution to be treated: the pH of the acidic solution has to be of the order of the apparent pK(a) of the membrane for appreciable content of active poly (4-vinylpydinium) groups and high selectivity of the ion transport through the membrane. (C) 2008 Elsevier B.V. All rights reserved.