Surface layer modification of AEMs by infiltration and photo‐cross‐linking to induce monovalent selectivity

Abstract

Surface modification of anion exchange membranes (AEMs) by attaching a negatively charged layer is the main method for preparing monovalent anion selective membranes. However, tremendous increase of membrane resistance and poor long‐term stability of the modified membranes face great challenges. In this work, a photosensitive molecule (4,4‐diazostilbene‐2,2‐disulfonic acid disodium salt [DAS]) was infiltrated into the membrane surface and immobilized in the structure by cross‐linking under UV irradiation. This method introduced negative charge to the surface layer of the AEMs without increasing membrane thickness, leading to high performance membrane with high monovalent anion selectivity. The optimized membrane (D‐5) shows the highest perm‐selectivity of 11.21, which is superior to the commercial selective membrane Selemion® ASV and previously reported monovalent anion selective AEMs. Furthermore, the newly developed membrane exhibits excellent long‐term stability, which can maintain constant selectivity during the 80 h ED experiment. © 2017 American Institute of Chemical Engineers AIChE J, 64: 993–1000, 2018

Design of Monovalent Ion Selective Membranes for Reducing the Impacts of Multivalent Ions in Reverse Electrodialysis

“…To overcome these challenges, other techniques, such as covalent immobilization of poly(ethyleneimine) (PEI) onto the surface of AEM [55], infiltration and cross-linking [57], and photoinduced covalent immobilization [58], were tested to form a stable linkage between the membrane and the modified layer. Covalent immobilization of PEI on AEM and partly quaternized poly(phenylene oxide) achieved excellent monovalent selectivity of (P Cl − SO 2− 4 = 4.…”

“…During continuous cycling for 70 h in the ED process, the concentration of the sulphate ion was higher than the chloride ion, showing excellent monovalent ions selectivity and stability of the modified membrane. Very recently, Liu et al modified AEM with 4,4-diazostilbene-2,2-disulfonic acid disodium salt [DAS] via infiltration and then covalent cross-linking using UV radiation [57]. As shown in Figure 8, the modified membrane had a negative charge toward the surface of the AEM, exhibiting the highest permselectivity of 11.21 compared with the commercial monovalent selective membrane (Selemion ASV) [49,63] and other reported modified AEMs (see Table 2) [48,49,55,58,59].…”

“…The azido group in DAS reacted to a nitrene group under UV irradiation which immobilized it on the membrane surface, thereby creating covalent cross-linking: The sulfonate group facilitated the water solubility and infiltration into the surface layer structure of the membrane, providing the negative charge groups and also improving the monovalent anion selectivity. Reproduced with permission from [57]. Copyrights 2018 American Institute of Chemical Engineers.…”

Surface Modifications of Anion Exchange Membranes for an Improved Reverse Electrodialysis Process Performance: A Review

“…In order to support the positive effects of modifying AEMs through the two methods above-mentioned, Figure 7 shows the Fourier-transform infrared spectroscopy (FTIR) spectra and the atomic force microscope (AFM) images of a commercial AEM (JMA-II-07), which was modified by infiltration (immersion), using 4,4-diazostilbene-2,2-disulfonic acid disodium salt (DAS) as the modifying agent, and UV-cross linking [70]. The FTIR revealed that both the infiltrated (uncross-linked D-5), and UV-crosslinked (D-5) membranes exhibited sulfonate absorption bands at 1200, 1130 and 1030 cm −1 .…”

“…Membranes 2020, 10, x FOR PEER REVIEW 15 of 22 infiltration (immersion), using 4,4-diazostilbene-2,2-disulfonic acid disodium salt (DAS) as the modifying agent, and UV-cross linking [70]. The FTIR revealed that both the infiltrated (uncrosslinked D-5), and UV-crosslinked (D-5) membranes exhibited sulfonate absorption bands at 1200, 1130 and 1030 cm −1 .…”