실란화합물을 이용한 폴리아마이드 역삼투막의 표면개질과 성능평가

Abstract

Reverse osmosis(RO) technology has been developed over the past 40 years to a 44% share in the world desalting production capacity, and an 80% share in the total number of desalination plants installed worldwide. Thin-film-composite membranes(TFCs) that contain aromatic polyamides(PAs) are widely used in commercial high-performance RO membranes and thus have been used for the desalination of seawater and brackish water. However, PA membranes are susceptible to fouling and chlorine exposure, which reduce permeate flux and salt rejection. The objective in this study is to improve the salt rejection, flux and fouling resistance of TFC polyamide RO membranes, which can be achieved via the surface modification of polyamides by silane compounds with functional groups. Commercial RO membranes(RE12040, Woongjin, Korea) were used as thin film composite polyamide membranes in this study. Membrane samples for experiments were flat sheets, peeled of the module. Alkoxysilanes used as coating reagents without further purification. Seawater salt(Coralife, 7000 ppm) was used to test the performance of the RO membranes. The typical mechanism of sol-gel condensation was applied using silane compounds. When an electron-drawing group is present on the polyamide chain, redox reactions would occur with the alkoxy group of silane compounds. The alkoxy group may act as a bridge to combine silane compounds with the polyamide through a chain of primary strongest interfacial bonds. The performance test showed that salt rejection of TMOHES-coated membranes were slightly improved due to the hydrophobic epoxy having hydrolyzed functional groups. On the other hand, permeate flux of AEAP-coated membranes were significantly improved test due to the hydrophilic amino having hydrolyzed functional groups.