Pervaporation Performance Of Composite Membranes Research Articles

The effect of bioadhesive on the interfacial compatibility and pervaporation performance of composite membranes by MD and GCMC simulation

Combing molecular dynamics (MD) and Grand Canonical Monte Carlo (GCMC) simulation, the effect of bioadhesive transition layer on the interfacial compatibility of the pervaporation composite membranes, and the pervaporation performance toward penetrant molecules were investigated. In our previous experimental study, the structural stability and permeability selectivity of the composite membranes were considerably enhanced by the introduction of bioadhesive carbopol (CP). In the present study, the interfacial compatibility and the interfacial energies between the chitosan (CS) separation layer, CP transition layer and the support layer were investigated, respectively. The mobility of polymer chains, free volume in bulk and interface regions were evaluated by the mean-square displacement (MSD) and free volume voids (FFV) analysis. The diffusion and sorption behavior of water/ethanol molecules in bulk and interface regions were characterized. The simulation results of membrane structure have good consistency, indicating that the introduction of CP transition layer improved the interfacial compatibility and interaction between the separation layer and the support layer. Comparing the bulk region of the separation layer, the mobility and free volume of the polymer chain in the interface region decreased and thus reduced the swelling of CS active layer, revealing the increased diffusion selectivity toward the permeated water and ethanol molecules. The strong hydrogen bonds interaction between the COOH of the CP transition layer and water molecules increased the adsorption of water molecules in the interface region. The simulation results were quite consistent with the experimental results.

Polydimethylsiloxane (PDMS) Membrane Filled with Biochar Core-shell Particles for Removing Ethanol from Water

A new type of biochar-SiO2 core-shell particles (BCNPs) was successfully prepared via the sol-gel-sediment method. The characteristics of BCNPs were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). This novel filler was added to a polydimethylsiloxane (PDMS) matrix to prepare composite membranes to separate ethanol from water via pervaporation (PV). The effect of BCNPs on the performance of the membranes was researched. Experimental results showed that the addition of BCNPs led to remarkably improved PV performance of composite membranes. When a BCNPs content was 5 wt.% for a 10 wt.% ethanol solution at 40 °C, the best PV performances gained were the separation factor of 11.9 and the corresponding permeation flux of 227 g·m-2·h-1.

The effect of metal complex on pervaporation performance of composite membrane for separation of n-butanol/water mixture

We prepared a PDMS/PVDF, a PDMS/PVDF-Fe(II) and a PDMS/PVDF-Co(II) membranes. Support layer was prepared by using polyvinylidene fluoride (PVDF)/N-methyl-2-pyrrolidone (NMP) casting solution with or without Fe(II) complex or Co(II) complex. Pervaporation performance was tested to determine the contribution of metal complex additives in the support layer. The flux and the separation factor of the PDMS/PVDF-Fe(II) complex membrane were 331.84g/m2h and 42, respectively. The flux of PDMS/PVDF membrane was 233.33g/m2h and separation factor was 44. The separation factor of PDMS/PVDF-Fe(II) complex membrane is similar to PDMS/PVDF membrane, the flux of the former is much higher than the latter.

Structure and performance characterization of PDMS/PES-based pervaporation membranes for ethanol/water separation

Composite membranes, with a supporting layer of polyethersulfone (PES) and different active layers based on poly(dimethylsiloxane) (PDMS), were prepared to perform pervaporative separation of ethanol from water. Two approaches were adopted to enhance the ethanol selectivity of PDMS by: (1) evaluation of the effects of PDMS viscosity of two different grades and (2) the incorporation of new hydrophobic silica in the active layer. First, the structural morphology of support and active layers of the composite membranes was characterized. AFM images were evidence of the nodular structure of the membrane surfaces. Mean pore size and pore size distribution of PES layer, mean nodular size of PDMS layer, and their surface roughness and water contact angle were determined. The relationship between these structural properties and the pervaporation performance of composite membranes has then investigated. The effects of operating parameters, feed concentration and temperature on the membrane performance indicated that increasing the feed temperature improved PDMS/PES membranes pervaporative efficiency. Based on the results obtained, it was found that PDMS viscosity influenced the pervaporation performance; low-viscosity PDMS had a greater separation factor and greater permeation fluxes than high-viscosity PDMS. Moreover, silica-filled membranes improved the separation factor and enhanced the ethanol flux relatively.

Enhancement of pervaporation performance of composite membranes through in situ generation of silver nanoparticles in poly(vinyl alcohol) matrix

ABSTRACTComposite membranes were prepared from an aqueous solution of poly(vinyl alcohol) (PVA) and silver sulphate. The silver nanoparticles were generated in situ before crosslinking PVA matrix by reduction of silver ions using sodium borohydride. Physico‐chemical properties of the resulting composite membranes were studied using Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy (UV–vis), thermogravimetric analysis (TGA), Wide‐angle X‐ray diffraction (WAXD), scanning electron microscopy (SEM), and universal testing machine (UTM). The UV–vis spectrum shows a single peak at 410 nm due to surface plasmon absorption of silver nanoparticles. This surely specified that silver nanoparticles are generated in PVA matrix. The membranes were under go pervaporation (PV) for separation of water from isopropanol at different temperatures. The results indicated that hydrophilicity and amorphous nature of the membranes were increased with increasing silver nanoparticles in PVA matrix. The swelling and separation performance of the membranes were studied. Both permeation flux and separation factor were increased with increasing silver nanoparticles in PVA matrix. The results showed that the membrane containing 2.5 mass% of Ag salt exhibited excellent PV performance. The values of total flux and flux of water are almost closed to each other, indicating that membranes could be effectively used to break the azeotropic point of water‐isopropanol. The long‐term test was performed at room temperature and ascertained that membranes were durable up to 30 days for the dehydration of IPA. On the basis of the estimate Arrhenius activation energy values, the efficiency of the membranes was discussed. The calculated ΔHs values are negative for all the membranes, indicating that Longmuir's mode of sorption is predominant. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41248.

Pervaporation dehydration of ethyl acetate aqueous solution using the doubly modified polyvinyl alcohol (PVA) composite membrane

Polyvinyl alcohol–tetraethoxysilane–perfluorosulfonic acid (PVA–TEOS–PFSA) hybrid membrane was prepared by sol–gel method through PVA being modified doubly by PFSA and TEOS. With polyacrylonitrile (PAN) ultrafiltration membrane as a substrate membrane, PVA–TEOS–PFSA/PAN composite membrane was fabricated by dip-coating method for pervaporation (PV) dehydration of ethyl acetate (EAc) aqueous solution. The hybrid membrane was characterized by swelling degree, static contact angle, Fourier transform infrared spectra and scanning electron microscope. Effects of PFSA and TEOS contents in coating solution on PV performance of composite membrane were investigated, respectively. With increasing PFSA content, the permeation flux of composite membrane increased, while the separation factor decreased. Just the opposite, the increase of TEOS content resulted in the decrease in permeation flux and the increase in separation factor. In addition, the PV performances of composite membranes were also investigated at different feed temperatures and water concentrations in feed, respectively. The PVA–TEOS–PFSA/PAN composite membrane, which was prepared from coating with PVA/PFSA mass ratio of 80/20 and TEOS content of 20 wt%, exhibited the permeation flux of 347.9 g m−2 h−1 and the separation factor of 2218 for PV dehydration of 2 wt% water of EAc solution at 40 °C.

Enhancing Structural Stability and Pervaporation Performance of Composite Membranes by Coating Gelatin onto Hydrophilically Modified Support Layer

The interfacial compatibility of composite membrane is an important factor to its structural stability and separation performance. In this study, poly (ether sulfone) (PES) support layer was first hydrophilically modified with poly(vinyl alcohol) (PVA) via surface segregation during the phase inversion process. Gelatin (GE) was then cast on the PVA-modified PES support layer as the active layer followed by crosslinking to fabricate composite membranes for ethanol dehydration. The enrichment of PVA on the surface of support layer improved interfacial compatibility of the as-prepared GE/PVA-PES composite membrane. The water contact angle measurement and X-ray photoelectron spectroscopy (XPS) data confirmed the surface segregation of PVA with a surface coverage density of ∼80%. T-peel test showed that the maximal force to separate the support layer and the active layer was enhanced by 3 times compared with the GE/PES membrane. The effects of PVA content in the support layer, crosslinking of GE active layer and operating parameters on the pervaporative dehydration performance were investigated. The operational stability of the composite membrane was tested by immersing the membrane in ethanol aqueous solution for a period of time. Stable pervaporation performance for dehydration of 90% ethanol solution was obtained for GE/PVA-PES membrane with a separation factor of ∼60 and a permeation flux of ∼1910 g·m−2·h−1 without peeling over 28 days immersion.

Pervaporation of Aqueous Solution of Acetaldehyde Through ZSM-5 Filled PDMS Composite Membrane

Hydrophobic ZSM-5 zeolite filled polydimethylsiloxane (PDMS) composite membranes with Nylon micro-filtration membrane as the support layer were prepared to separate acetaldehyde from its aqueous solution. The composite membranes were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. Their structural morphology and thermal stability were also examined. The swelling study showed that the composite membranes presented higher degree of swelling in aqueous solution of acetaldehyde than in pure water at 25°C, suggesting that the membranes have stronger sorption capacity in acetaldehyde solution. The effects of ZSM-5 filling content and acetaldehyde concentration on pervaporation performance of composite membranes were investigated. The permeation experiments at different temperatures showed that both selectivity and permeation flux of composite membranes increased with temperature. With 5%ZSM-5-PDMS/Nylon membrane at acetaldehyde mass concentration of 8% and 25°C, the separation factor of acetaldehyde/water achieved 35 and the permeation flux was 233.3 g·m−2·h−1.

A novel atmospheric dielectric barrier discharge (DBD) plasma graft-filling technique to fabricate the composite membranes for pervaporation of aromatic/aliphatic hydrocarbons

A double-plasma grafting strategy for the fabrication of the “pore-filling” composite membranes was proposed herein. By means of atmospheric dielectric barrier discharge (DBD) plasma, the graft copolymer was covalently anchored in the sublayer pores and onto the surface of the asymmetric polyacrylonitrile (PAN) ultrafiltration (UF) membrane through the combination of syn-irradiation grafting and postirradiation grafting of macromonomer poly(ethylene glycol) methacrylate (PEO526OHMA), consequently, a “pore-filling” composite membrane for pervaporation of aromatic/aliphatic hydrocarbons was obtained. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurements (WCA), and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) were utilized to characterize the composite membrane. The effects of DBD irradiation time, DBD input voltage, macromonomer concentration on the degree of grafting and pervaporation performance of composite membrane for the toluene/n-heptane mixtures (1:4 in mass) at 80°C were investigated. Separation factor αtoluene/n-heptane up to 7.8 and permeate flux up to 1.62kg/m2h were achieved.

Preparation and pervaporation performance of surface crosslinked PVA/PES composite membrane

This study describes the facile preparation of poly(vinyl alcohol) (PVA)/polyethersulfone (PES) composite membranes by interfacial reaction technique, aiming at acquiring the improved structural and operational stability of the resulting membranes. The effect of interfacial crosslinking agent and hydrophilicity of support layer on the interfacial adhesive strength and pervaporation performance of composite membranes were investigated. The optimal recipe for PVA/PES composite membrane preparation was as follows: PES support layer was treated with 0.1 wt.% borax aqueous solution, fully dried and then immersed into 2 wt.% PVA aqueous solution. The resulting PVA active layer was 1–1.5 μm thick after twice dip-coating. The as-prepared PVA/PES composite membrane exhibited high separation factor of over 438, high permeation flux of 427 g m −2 h −1 for 80 wt.% EG in the feed at 70 °C and desirable structural stability. It could be derived that adoption of interfacial reaction would be an effective method for preparing the composite membranes suitable for large-scale dehydration of ethylene glycol/water mixture.