Enhancing Chlorine Resistances And Anti-biofouling Properties Of Composite Reverse Osmosis Membranes By ADMH And MBA Modification

To enhance the chlorine resistance and anti-biofouling property of aromaticpolyamide reverse osmosis (RO) membrane, Ph.D Xinyu Wei grafted3-allyl-5,5-dimethylhydantoin (ADMH) onto commercial aromatic polyamidecomposite RO membranes successfully. However, the graft content of ADMH onmembrane surface was limited for the self-inhibition of allyl unit on ADMH duringgraft polymerization. To solve this problem, commercial RO membranes weremodified by graft polymerization of ADMH and N,N′-Methylenebis (acrylamide)(MBA) associatively. MBA could link ADMH groups onto membrane surfaces andincrease the graft content of ADMH. As a result, the membrane chlorine resistanceand anti-biofouling property would be further enhanced.The graft monomer concentration, initiator concentration, reaction temperature andtime in graft polymerization were optimized for manufacturing ADMH and MBAmodified membrane. ADMH-modified membrane and MBA-modified membranewere prepared to discover the respective effects of ADMH and MBA on modifiedmembrane performance. The membrane physicochemical properties such as surfacefunctional groups, element contents, and hydrophilicity were analyzed before andafter graft polymerization. The permeability and selectivity, chlorine resistance,antimicrobial and anti-biofouling property of raw and modified membranes wereevaluated.ATR-FTIR verified the successful modification of ADMH and MBA on membranesurface. Based on XPS and contact anglel measurements, graft polymerizationincreased the nitrogen atom content and surface hydrophilicity of the membrane. Thesalt rejections of the modified membranes were nearly unchanged compared withthose of the raw membranes, but the water fluxes of membranes decreased after graftpolymerization. After three chlorination and sterilization cycles, slighter changes wereobserved in water fluxes, salt rejections and sterilization effects on Escherchia coli ofthe modified membranes compared with the raw membranes. The chlorine resistancesand anti-biofouling abilities of the modified membranes were much better than theraw membranes. Additionally, the repeatability on chlorine resistances andanti-biofouling properties of modified membranes was realizable in chlorination and sterilization cycles.