Titorova Valentina, Sabbatovskiy Konstantin, Sarapulova Veronika, Kirichenko Evgeniy, Sobolev Vladimir, Kirichenko Ksenia
Membrane Institute, Kuban State University, 149 Stavropolskaya st., 350040 Krasnodar, Russia.
Frumkin Institute of Physical Chemistry and Electrochemistry RAS, 31 Leninsky prospect, 119071 Moscow, Russia.
Membranes (Basel). 2020 Jan 27;10(2):20. doi: 10.3390/membranes10020020.
Coating of ion exchange membranes used in electrodialysis with layers of polyelectrolytes is a proven approach that allows for the increasing of the limiting current, the suppressing of sedimentation, the controlling of the intensity of generation of H and OH ions, and also the improving of monovalent selectivity. However, in the case when two materials with the opposite sign of the charge of fixed groups come in contact, a bipolar boundary is created that can cause undesirable changes in the membrane properties. In this work, we used a MK-40 heterogeneous membrane on the surface of which a layer of polyethyleneimine was applied by adsorption from a solution as a model of heterogeneous membranes modified with oppositely charged polyelectrolyte. It was found that, on one hand, the properties of modified membrane were beneficial for electrodialysis, its limiting current did not decrease and the membrane even acquired a barrier to non-selective electrolyte transport. At the same time, the generation of H and OH ions of low intensity arose, even in underlimiting current modes. It was also shown that despite the presence of a layer of polyethyleneimine, the surface charge of the modified membrane remained negative, which we associate with low protonation of polyethyleneimine at neutral pH.
用电解质层对电渗析中使用的离子交换膜进行涂覆是一种行之有效的方法，它可以提高极限电流、抑制沉淀、控制H和OH离子的产生强度，还能提高单价选择性。然而，当两种固定基团电荷符号相反的材料接触时，会形成一个双极边界，这可能会导致膜性能出现不良变化。在这项工作中，我们使用了MK-40异质膜，在其表面通过从溶液中吸附施加了一层聚乙烯亚胺，作为用带相反电荷的聚电解质改性的异质膜模型。结果发现，一方面，改性膜的性能有利于电渗析，其极限电流没有降低，并且该膜甚至对非选择性电解质传输形成了屏障。同时，即使在低于极限电流模式下，也会产生低强度的H和OH离子。研究还表明，尽管存在一层聚乙烯亚胺，但改性膜的表面电荷仍为负，我们将此归因于聚乙烯亚胺在中性pH下的低质子化。
