Acrylic acid grafting of polyethylene hollow fiber membranes in a module scale via long-distance and dynamic low-temperature plasma flow

Long-distance and dynamic Ar low-temperature plasma flow pretreatment of polyethylene(PE) membrane in a module scale and subsequent acrylic acid(AA) grafting in aqueous solutions were developed to prepare hydrophilic PE hollow fiber membrane modules(PE-g-AA) successfully. This novel plasma chemical modification exhibited high efficiency, environment-friendly process and low surface etching. In the PE-g-AA membrane module, almost all contact angles along with fiber axial distance from the plasma inlet for outside membrane surfaces were close to 50°, far smaller than that of virgin membranes(about 120°). The improvement in surface hydrophilicity of PE-g-AA membrane was mainly due to the chemically grafted implantation of a large amount of -COOH polar groups onto outside membrane surfaces. Meanwhile, the uniform of chemistry and morphology for outside PE-g-AA membrane surfaces was improved greatly. Moreover, after 7 times water filtrations during 120 d storage, the steady water flux of PE-g-AA module was still about 1.5 times of that of virgin one, and its average contact angle recovered by only about 8°. The PE-g-AA module exhibited good hydrophilic stability. Also, the grafting reduced bovine serum albumin(BSA) fouling and increased pure water flux. After cleaning, the pure water flux of fouled PE-g-AA module during filtration of BSA aqueous solution can recover to about 81.79% of that of before fouling.