Efficient Anion-Exchange Membranes with Anti-Scaling Properties Obtained by Surface Modification of Commercial Membranes Using a Polyquaternium-22

Abstract

Anion-exchange membranes modified with a polyquaternium-22 (PQ-22) polymer were studied for their use in electrodialysis. The use of PQ-22 for modification makes it possible to “replace” weakly basic amino groups on the membrane surface with quaternary amino groups. It was found that the content of quaternary amino groups in PQ-22 is higher than the content of carboxyl groups, which is the reason for the effectiveness of this polymer even when modifying Ralex AHM-PES membranes that initially contain only quaternary amino groups. In the case of membranes containing weakly basic amino groups, the PQ-22 polymer modification efficiency is even higher. The surface charge of the modified MA-41P membrane increased, while the limiting current density on the current-voltage curves increased by more than 1.5 times and the plateau length decreased by 2.5 times. These and other characteristics indicate that the rate of water splitting decreased and the electroconvective mixing at the membrane surface intensified, which was confirmed by direct visualization of vortex structures. Increasing the surface charge of the commercial MA-41P anion-exchange membrane, reducing the rate of water splitting, and enhancing electroconvection leads to mitigated scaling on its surface during electrodialysis.

Interplay between Forced Convection and Electroconvection during the Overlimiting Ion Transport through Anion-Exchange Membranes: A Fourier Transform Analysis of Membrane Voltage Drops

“…It is interesting to note that the range of currents at which changes in pH were noticed are similar for both membranes and at different degrees of stirring. In previous works, a similar evolution of pH was registered, but changes in pH started from current densities near [ 33 , 34 ].…”

Water treatment and reclamation by implementing electrochemical systems with constructed wetlands

“…To solve that trade-off, material scientists are called to develop affordable electrodes that can promote oxidant generation and be cathodically and anodically stable. When membrane-divided cells are implemented, developing costcompetitive ion-exchange membranes resistant to oxidants, highly conductive, and with anti-fouling properties is also encouraged [32,184].…”

Stability of Ion Exchange Membranes in Electrodialysis

“…Precipitates are usually formed by CaCO 3 [ 36 ], CaSO 4 [ 26 ] and other insoluble sulfates (BaSO 4 , more rarely SrSO 4 and RaSO 4 ) [ 37 ], Ca(OH) 2 and Mg(OH) 2 [ 38 ], which are sparingly soluble compounds; therefore, it is noteworthy that that the formation of these precipitates can occur not only in the concentration chamber, but also in the desalination chamber. An example of the precipitates formed at the side of MA-41P membrane [ 39 ] in a solution of the following composition (Li + ~0.25 g/L, Na + ~1.15 g/L, K + ~2.5 g/L, Ca 2+ ~1.5 g/L, Mg 2+ ~0.3 g/L, HCO 3 − ~4.3 × 10 −3 g/L, Cl − ~8.86 g/L and pH 3.9) facing the desalination chamber is shown in Figure 3 .…”

“…Reprinted with permission from Ref. [ 39 ] under the terms of the Creative Commons Attribution 4.0 International License ( (accessed on 26 December 2022)). Copyright © 2022 by the authors.…”