Abstract
A facile membrane surface modification process for improving permselectivity and antimicrobial property was proposed. A polydopamine (PDA) coating was firstly fabricated on pristine anion exchange membrane (AEM), followed by in situ reduction of Ag without adding any extra reductant. Finally, 2,5-diaminobenzene sulfonic acid (DSA) was grafted onto PDA layer via Michael addition reaction. The as-prepared AEM exhibited improved permselectivity (from 0.60 to 1.43) and effective inhibition of bacterial growth. In addition, the result of the long-term (90-h continuous electrodialysis) test expressed the excellent durability of the modified layer on membrane surface, because the concentration of Cl− and SO42− in diluted chamber fluctuated ~0.024 and 0.030 mol·L−1 with no distinct decline. The method described in this work makes the full use of multifunctional PDA layer (polymer-like coating, in situ reduction and post-organic reaction), and a rational design of functional AEM was established for better practical application.
Highlights
Increasing population nowadays accelerates the crisis of fresh water resources [1]
To endow the membranes with permselectivity, 2,5-diaminobenzene sulfonic acid (DSA), which is rich in amino functional groups, was used as a reactive carrier containing sulfonic acid, and can react with polydopamine by Michael addition [28]
After the ultraviolet-induced Michael addition, DSA was grafted onto the membrane surface with a polydopamine layer
Summary
Increasing population nowadays accelerates the crisis of fresh water resources [1]. Seawater, accounting for 97% of the world’s water resources, can provide sustainable clean water after removing salts and other impurities. The result turned out that the monovalent anion selectivity increased to 2.9 and the separation efficiency increased to 0.28 with nine bilayers due to the accumulated surface negative charge. Mulyati [18] and coworkers reported a modified AEM with an odd number of layer-by-layer layers (poly(sodium 4-styrene sulfonate) top layer), which, if above 15, had sufficient monovalent anion selectivity for practical use, and showed high antifouling potential. Common AEMs with positive charged ion exchange groups inside the membrane attract bacteria when treating raw water with microorganisms. Surface modification of the membrane has a great effect on enhancing the antibacterial property by limiting the adhesion of microorganisms or by killing the bacterial. A novel AEM was fabricated with antibacterial property and monovalent selectivity simultaneously. The Ag nanoparticles on membrane surface significantly enhanced the antibacterial property
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