Surface Molecular Functionalization And Amphoteric Ionization Modified QPPO ??anion Exchange Membrane

With the widespread application of electrodialysis technology in various water systems,the problem of electrodialysis membrane contamination is gradually being put on the agenda.Domestic and foreign scientific research workers have also conducted in-depth research and exploration of the pollution phenomenon itself.And so on,the main target is inorganic pollution and cannot solve the problem of organic pollution.For organic pollution problems(mainly present on anion exchange membranes(AEMs)),researchers are working hard to develop anti-organic contamination type anion exchange membranes(AEMs).(1)The suppression of anion exchange membrane(AEMs)fouling has been a severe challenge faced by membrane applications(e.g.,electrodialysis,ED).In this study,a novel AEMs modified with dual functional layers has been prepared by coating hydrophilic polydopamine(PDA)on quaternized poly(2,6-dimethyl-1,4-phenylene oxide)(QPPO)and subsequently grafting with zwitterionic structure of sulfobetaine methacrylate(SBMA)via the aza-Michael reaction,aiming to improve the fouling resistant.In particular,the sodium dodecyl benzene sulfonate(SDBS)was used as the model foulant.The hydrophilic layer(PDA)and hydrophilic/negatively-charged zwitterionic surface of AEMs,serving as a useful barrier via physical blocking and electrostatic repulsion,respectively,significantly suppress the deposition and/or chemical adsorption of SDBS.The time elapsed until the occurrence of fouling(critical time)of optimized modified Q-P18-S AEMs(376 min)is much 75 and 5.3 times longer than those of the original QPPO AEMs and PDA modified AEMs without zwitterionic layer,respectively,suggestive of the superior fouling resistant.This has been further confirmed by the much less drop percentage of NaCl removal ratios of ED without and with SDBS from Q-P18-S(3.66% vs.13.78% from commercial JAM-II-05 AEMs).(2)Utilizing mussel-inspired molecular functionalization and zwitterionic design,a simple,versatile and novel method was developed to prepare anion exchange membranes that are resistant to organic conta mination.The surface of an anion exchange membrane(AEMs)is coated with a polydopamine(PDA)coating,and the primary amine group and the tertiary amine group on the active molecule N,N-dimethylethylenediamine(DMDA)are subjected to a Michael addition reaction to graft.The DMDA functionalization is further reacted with 1,3-propane sultone to obtain two ion exchange membranes.After the surface molecule is functionalized,the membrane becomes more hydrophilic due to the strong surface hydration of PDA and zwitterionic functional groups.The time elapsed until the occurrence of fouling(critical time)of modified Q-P2 DZ AEMs(246 min)is much 50 times longer than original QPPO AEMs without zwitterionic layer,suggestive of the superior fouling resistant.This has been further confirmed by the much higher percentage of NaCl removal ratios of ED with SDBS from Q-P2 DZ AEMs(45.8%)compared with QPPO AEMs(10%).