title: Silylated mesoporous silica membranes on polymeric hollow fiber supports: synthesis and permeation properties.
abstract: We report the synthesis and organic/water separation properties of mesoporous silica membranes, supported on low-cost and scalable polymeric (polyamide-imide) hollow fibers, and modified by trimethylsilylation with hexamethyldisilazane. Thin (∼1 μm) defect-free membranes are prepared, with high room-temperature gas permeances (e.g., 20,000 GPU for N2). The membrane morphology is characterized by multiple techniques, including SEM, TEM, XRD, and FT-ATR spectroscopy. Silylation leads to capping of the surface silanol groups in the mesopores with trimethylsilyl groups, and does not affect the integrity of the mesoporous silica structure and the underlying hollow fiber. The silylated membranes are evaluated for pervaporative separation of ethanol (EtOH), methylethyl ketone (MEK), ethyl acetate (EA), iso-butanol (i-BuOH), and n-butanol (n-BuOH) from their dilute (5 wt %) aqueous solutions. The membranes show separation factors in the range of 4-90 and high organic fluxes in the range of 0.18-2.15 kg m(-2) h(-1) at 303 K. The intrinsic selectivities (organic/water permeability ratios) of the silylated membranes at 303 K are 0.33 (EtOH/water), 0.5 (MEK/water), 0.25 (EA/water), 1.25 (i-BuOH/water), and 1.67 (n-BuOH/water) respectively, in comparison to 0.05, 0.015, 0.005, 0.08, and 0.14 for the unmodified membranes. The silylated membranes allow upgradation of water/organics feeds to permeate streams with considerably higher organics content. The selective and high-flux separation is attributed to both the organophilic nature of the modified mesopores and the large effective pore size. Comparison with other organics/water separation membranes reveals that the present membranes show promise due to high flux, use of scalable and low-cost supports, and good separation factors that can be further enhanced by tailoring the mesopore silylation chemistry.
authors.affiliation: School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , 311 Ferst Drive, Atlanta, Georgia 30332-0100, United States.
authors.forename: Hyung-Ju
authors.initials: HJ
authors.lastname: Kim
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Brunelli
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Brown
authors.forename: Kwang-Suk
authors.initials: KS
authors.lastname: Jang
authors.forename: Wun-gwi
authors.initials: WG
authors.lastname: Kim
authors.forename: Fereshteh
authors.initials: F
authors.lastname: Rashidi
authors.forename: Justin R
authors.initials: JR
authors.lastname: Johnson
authors.forename: William J
authors.initials: WJ
authors.lastname: Koros
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Jones
authors.forename: Sankar
authors.initials: S
authors.lastname: Nair
keywords: hollow fiber; membrane; mesoporous silica; organics/water separation; silylation