Dependence of Electrochemical Properties of MK-40 Heterogeneous Membrane on Number of Adsorbed Layers of Polymers

Abstract

The creation of monovalent selective ion exchange membranes benefits the desalination of surface waters by removing interfering monovalent ions while preserving polyvalent ionic nutrients. Studies of a promising method of layer-by-layer adsorption of polymers for the creation of monovalent selective coatings note a significant effect of the number of formed layers and of the nature of the external layer on the properties of the resulting membranes. This article reports the changes in properties of layer-by-layer coated heterogeneous membranes occurring at increasing numbers of layers that are attributed to the supposed intermixing of polymers between the layers, namely dependence of limiting current densities determined from i-V curve, enhanced electroconvection that was attributed to the appearing electrical heterogeneity of the surface, and the decreasing monovalent selectivity in electrodialysis of mixed NaCl + CaCl2 solution (from 1.33 to about 1) between the samples with five and six to eight layers of polymers.

Stability of Properties of Layer-by-Layer Coated Membranes under Passage of Electric Current

“…The technique for membrane modification by layer-by-layer coating is based on the technique described in [ 38 ], and was also used in our previous work [ 39 ]. The membranes were modified as follows.…”

“…To determine the electrochemical properties of the membranes, i-V curves of the membranes were recorded using a laboratory grade four-chamber flow-through electrodialysis cell. The procedure of registration of the i-V curves and the cell were the same as in our previous work [ 39 ]. The cell consisted of four chambers separated by the membranes (one studied membrane, one auxiliary MK-40 cation exchange membrane to separate the cathodic chamber and one auxiliary MA-41 anion exchange membrane from the same manufacturer to separate the anodic chamber) with a total area of 5 × 5 cm 2 , a polarized area of 2 × 2 cm 2 , and an intermembrane distance of 0.65 cm.…”

“…The studied membrane is shown as 1, 2 and 3 are the auxiliary anion exchange and cation exchange membranes, respectively, 4 are the polarizing electrodes attached to the plexiglass plate, 5 is a rubber o-ring, 0.075 cm thick in assembled state, 6 is a plexiglass frame 0.5 cm thick, 7 is the desalination chamber, 8 is the concentration chamber, 9 are the electrode chambers, 10 is a Luggin capillary, 11 are the Ag/AgCl electrodes, 12 are the power source and a multimeter, 13 is the circulation tank of a desalination tract, 14 is the circulation tank of a concentration tract, 15 is the circulation tank of electrode tract, 16 is the multichannel pump. The figure is reproduced from our previous article [ 39 ].…”

Short-Term Stability of Electrochemical Properties of Layer-by-Layer Coated Heterogeneous Ion Exchange Membranes

“…Dashed line shows the flow inlet and the outlet of the desalination chamber. The figure is an adaptation of the scheme from our previous article [ 55 ] (adapted under the terms of the Creative Commons Attribution 4.0 International License ( , 20 November 2022)).…”