Poly(ether sulfone) supported hybrid poly(vinyl alcohol)–maleic acid–silicone dioxide membranes for the pervaporation separation of ethanol–water mixtures

Microporous poly(ether sulfone) (PES) supported hybrid polymer–inorganic membranes were prepared by the crosslinking of poly(vinyl alcohol) (PVA), maleic acid (MA), and SiO₂ via an aqueous sol–gel route and a solution‐casting method. The membrane performance was tested for the pervaporation separation of ethanol–water mixtures from 20 to 60 °C with a feed ethanol concentration of 96 wt %. The membrane characterization results reveal that different SiO₂ loadings affected the crystallinity and roughness of the membranes. The PVA–MA–SiO₂ membrane containing 10 wt % SiO₂ showed that SiO₂ nanoparticles were well dispersed within the polymer matrix; this resulted in significant enhancements in both the flux and selectivity. The membrane achieved a high water permeability of 1202 g·μm·m^?2 h^?1 kPa^?1 and a selectivity of 1027 for the separation of a 96 wt % ethanol‐containing aqueous solution. This enhanced membrane performance might have been due to the dense crosslinking membrane network, increased free volume, and uniform distribution of SiO₂ nanoparticles. Both the water and ethanol fluxes increased with the feed water concentration and temperature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44839.     

Fabrication of efficient pervaporation desalination membrane by reinforcement of poly(vinyl alcohol)–silica film on porous polysulfone hollow fiber

Pervaporation membrane technology is commercially successful in the dehydration of organic solvents, and the technology has potential for seawater desalination with high recovery because of its capability to treat highly saline water. But to make the technology advantageous over the other available membrane desalination technologies in terms of productivity flux without additional energy cost, the selective barrier layer is required to be extremely thin, defect‐free, hydrophilic, and selective to water. In this work, we prepared an efficient membrane by reinforcing a highly water‐permeable but continuous barrier layer of poly(vinyl alcohol)–silica (PVA‐SiO₂) hybrid material on porous polysulfone hollow fibers. The PVA‐SiO₂ in acidified and hydrated ethanol was aged at room temperature for a period to allow solvent evaporation to obtain the solution concentration desired for the reinforcement. The reinforced hollow fiber membrane with optimal PVA‐SiO₂ barrier layer thickness exhibited a performance with a flux of 20.6 L m^?2 h^?1 and 99.9% salt rejection from a saline feed of 2000 ppm NaCl at 333 K. The effects of PVA‐SiO₂, temperature, and feed salinity on the pervaporation performance of the membrane were also studied. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45718.     

Nano-Modification of the Polyvinyl Alcohol/Organic Acid-Modified Polyvinylidene Fluoride Thin-Film Composite Membrane and Its Application in the Nanofiltration Process

In this study, a novel thin-film nanocomposite (TFN) membrane is developed consisting of a cross-linked nano-modified polyvinyl alcohol (PVA) selective layer on an organic acid-modified polyvinylidene fluoride (PVDF) membrane. The nano-modification of the PVA layer is performed via incorporating different amounts of the amine-functionalized multiwalled carbon nanotubes (MWCNTs-NH₂) into the PVA matrix. The effect of citric acid on the chemical structure and morphology of the PVDF support is also investigated. The performance of the resultant membranes in the nanofiltration (NF) of MgSO₄ and acid yellow-17 aqueous solutions is also studied. The results indicate that the modification of the support with 0.5 wt% of citric acid increased the water permeance from 1.59 L m⁻² h⁻¹ bar⁻¹ (LMH/bar) for PVA/PVDF to 4.49 LMH/bar for the PVA/modified PVDF membrane. Furthermore, the optimum value of MWCNT-NH₂ (0.6 wt%) increases the permeance of the resultant TFN membrane to 4.94 LMH/bar while maintaining a high rejection. Interestingly, the incorporation of MWCNT-NH₂ into the PVA layer and citric acid into the PVDF solution results in a membrane with the highest permeance of 6 LMH/bar.     

Preparation of poly(methyl methacrylate)‐Silica nanoparticles via differential microemulsion polymerization and physical properties of NR/PMMA‐SiO2 hybrid membranes

Poly(methy methacrylate) (PMMA)‐SiO₂ nanoparticles were prepared via differential microemulsion polymerization. The effects of silica loading, surfactant concentration, and initiator concentration on monomer conversion, particle size, particle size distribution, grafting efficiency, and silica encapsulation efficiency were investigated. A high monomer conversion of 99.9% and PMMA‐SiO₂ nanoparticles with a size range of 30 to 50 nm were obtained at a low surfactant concentration of 5.34 wt% based on monomer. PMMA‐SiO₂ nanoparticles showed spherical particles with a core‐shell morphology by TEM micrographs. A nanocomposite membrane from natural rubber (NR) and PMMA‐SiO₂ emulsion was studied for mechanical and thermal properties and pervaporation of water‐ethanol mixtures. PMMA‐SiO₂ nanoparticles which were uniformly dispersed in NR matrix, significantly enhanced mechanical properties and showed high water selectivity in permeate flux. Thus, the NR/PMMA‐SiO₂ hybrid membranes have great potential for pervaporation process in membrane applications. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

热处理条件对PVA/PAN和PPVA/PAN渗透汽化复合膜分离性能的影响

制备了以聚乙烯醇（PVA）、磷酸酯化聚乙烯醇（PPVA）和活性分离层的PVA／PAN、PPVA／PAN渗透汽化复合膜并用于乙醇－水恒沸混合物的分离。考察了热处理条件对复合膜分离性能及吸附性能的影响。结果表明,复合膜的分离性能主要是由热处理温度决定的,并且,PPVA／PAN复合膜比PVA／PAN复合膜具有更好的分离性能。确定了最佳的热处理条件,对于PVA／PAN复合膜：在403K下,热处理时间不小于4h,对于PPAV／PAN复合膜：在423K下,热处理时间不小于2h。     

Composite membranes from polyacrylonitrile with poly(N,N-dimethylaminoethyl methacrylate)-grafted silica nanoparticles as additives

Polyacrylonitrile (PAN)-based composite membranes were prepared by immersion precipitation method by using poly(N,N-dimethylaminoethyl methacrylate)-grafted silica (PDMAEMA@SiO₂) nanoparticles as hydrophilic additives. The molecular weight of PDMAEMA were controlled by the surface initiated atom transfer radical polymerization of N,N-dimethylaminoethyl methacrylate on SiO₂ nanoparticles. The synthesized nanoparticles have a typical core–shell structure as characterized in detail by FT-IR, TEM, DLS and GPC. The prepared PAN-based composite membranes have higher porosity and water permeation flux than those of the pure PAN membranes. They also show high rejection (⩾90%) to bovine serum albumin and high flux recovery ratio (⩾90%) to water permeation. These improved performances are attributed to the good hydrophilicity of PDMAEMA@SiO₂ nanoparticles. The results suggest that PDMAEMA@SiO₂ nanoparticles are suitable for the property optimization of PAN-based composite membranes.     

Synthesis of Gold-Platinum Core-Shell Nanoparticles Assembled on a Silica Template and Their Peroxidase Nanozyme Properties

Bimetallic nanoparticles are important materials for synthesizing multifunctional nanozymes. A technique for preparing gold-platinum nanoparticles (NPs) on a silica core template (SiO₂@Au@Pt) using seed-mediated growth is reported in this study. The SiO₂@Au@Pt exhibits peroxidase-like nanozyme activity has several advantages over gold assembled silica core templates (SiO₂@Au@Au), such as stability and catalytic performance. The maximum reaction velocity (V_max) and the Michaelis–Menten constants (K_m) were and 2.1 × 10⁻¹⁰ M⁻¹∙s⁻¹ and 417 µM, respectively. Factors affecting the peroxidase activity, including the quantity of NPs, solution pH, reaction time, and concentration of tetramethyl benzidine, are also investigated in this study. The optimization of SiO₂@Au@Pt NPs for H₂O₂ detection obtained in 0.5 mM TMB; using 5 µg SiO₂@Au@Pt, at pH 4.0 for 15 min incubation. H₂O₂ can be detected in the dynamic liner range of 1.0 to 100 mM with the detection limit of 1.0 mM. This study presents a novel method for controlling the properties of bimetallic NPs assembled on a silica template and increases the understanding of the activity and potential applications of highly efficient multifunctional NP-based nanozymes.     

A polyvinyl alcohol-based mixed matrix membrane with uniformly distributed Schiff base network-1 for ethanol dehydration

In this study, Schiff base network (SNW)-1 nanoparticles with high hydrophilicity and large specific surface area were used to prepare polyvinyl alcohol (PVA)-based mixed matrix membranes (MMMs), which were evaluated for ethanol dehydration. Because of the low difference of density between SNW-1 and PVA, the as-prepared nanoparticles can be uniformly distributed into the PVA active layer. The effects of SNW-1 loading, feed temperature, and water concentration on pervaporation (PV) performance were further studied. The results showed the MMM with 10 wt% of SNW-1 loading exhibited a separation factor of 1,501 and a permeation flux of 187 g m⁻² h⁻¹ for feeding 95 wt% ethanol/water binary solution at 75°C. Overall, the SNW-1/PVA MMMs showed great prospect in ethanol dehydration via PV.     

Pervaporation of ethanol/water and benzene/cyclohexane mixtures using novel substituted polyacetylene membranes

Summary In the ethanol/water pervaporation using membranes of Si-containing polymers, poly[1-phenyl-2-(p-trimethylsilyl)phenylacetylene] and poly[1-β-naphthyl-2-(p-trimethylsilyl)phenylacetylene], these polymer membranes permeated ethanol preferentially; α_EtOH/H2O 6.86 and 5.30, respectively, at 10 wt% EtOH content in the feed. Membranes of hydrocarbon-based polymers, poly(diphenylacetylene) and poly(1-β-naphthyl-2-phenylacetylene), which were prepared by desilylation of the two Si-containing polymer membranes, also exhibited ethanol permselectivity in ethanol/water pervaporation; α_EtOH/H2O 5.95 and 3.79, respectively. Further, in benzene/cyclohexane pervaporation, these desilylated membranes, which were insoluble in any organic solvent, showed rather low benzene permselectivity but very large fluxes. The results of the present study are attributed to the presence of many microvoids and, in turn, sparse structures. Received: 6 March 2002/ Accepted: 28 March 2002     

Electrical and optical properties of Al-doped ZnO and ZnAl2O4 films prepared by atomic layer deposition

ZnO/Al₂O₃ multilayers were prepared by alternating atomic layer deposition (ALD) at 150°C using diethylzinc, trimethylaluminum, and water. The growth process, crystallinity, and electrical and optical properties of the multilayers were studied with a variety of the cycle ratios of ZnO and Al₂O₃ sublayers. Transparent conductive Al-doped ZnO films were prepared with the minimum resistivity of 2.4 × 10⁻³ Ω·cm at a low Al doping concentration of 2.26%. Photoluminescence spectroscopy in conjunction with X-ray diffraction analysis revealed that the thickness of ZnO sublayers plays an important role on the priority for selective crystallization of ZnAl₂O₄ and ZnO phases during high-temperature annealing ZnO/Al₂O₃ multilayers. It was found that pure ZnAl₂O₄ film was synthesized by annealing the specific composite film containing alternative monocycle of ZnO and Al₂O₃ sublayers, which could only be deposited precisely by utilizing ALD technology.     

Poly(vinyl alcohol)/ZIF‐8‐NH2 mixed matrix membranes for ethanol dehydration via pervaporation

Ethanediamine‐modified zeolitic imidazolate framework (ZIF)‐8 particles (ZIF‐8‐NH₂) is synthesized and incorporated in the poly(vinyl alcohol) (PVA) matrix to fabricate novel PVA/ZIF‐8‐NH₂ mixed matrix membranes (MMMs) for pervaporation dehydration of ethanol. The PVA/ZIF‐8‐NH₂ MMMs exhibit enhanced membrane homogeneity and separation performance because of the higher hydrophilicity and restricted agglomeration of the particles, as compared to corresponding MMMs loaded with unmodified particles. The effect of ZIF‐8‐NH₂ loading in the MMMs is studied and the MMM with a 7.5 wt % ZIF‐8‐NH₂ loading shows the best pervaporation performance for ethanol dehydration at 40°C. Various characterization techniques (Fourier transform infrared, scanning electron microscope, contact angle, sorption test, etc.) are used to investigate the MMMs loaded with ZIF‐8 and ZIF‐8‐NH₂ particles. The impact of operation conditions on pervaporation performance is also performed. The performance benchmarking shows that the MMMs have superior separation factors and comparable flux to most other PVA hybrid membranes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1728–1739, 2016     

Effects of poly (vinyl alcohol) (PVA) content on preparation of novel thiol-functionalized mesoporous PVA/SiO2 composite nanofiber membranes and their application for adsorption of heavy metal ions from aqueous solution

Thiol-functionalized mesoporous poly (vinyl alcohol)/SiO₂ composite nanofiber membranes and pure PVA nanofiber membranes were synthesized by electrospinning. The results of Fourier transform infrared (FTIR) indicated that the PVA/SiO₂ composite nanofibers were functionalized by mercapto groups via the hydrolysis polycondensation. The surface areas of the PVA/SiO₂ composite nanofiber membranes were >290 m²/g. The surface areas, pore diameters and pore volumes of PVA/SiO₂ composite nanofibers decreased as the PVA content increased. The adsorption capacities of the thiol-functionalized mesoporous PVA/SiO₂ composite nanofiber membranes were greater than the pure PVA nanofiber membranes. The largest adsorption capacity was 489.12 mg/g at 303 K. The mesoporous PVA/SiO₂ composite nanofiber membranes exhibited higher Cu²⁺ ion adsorption capacity than other reported nanofiber membranes. Furthermore, the adsorption capacity of the PVA/SiO₂ composite nanofiber membranes was maintained through six recycling processes. Consequently, these membranes can be promising materials for removing, and recovering, heavy metal ions in water.     

PFSA-TiO2(or Al2O3)-PVA/PVA/PAN difunctional hollow fiber composite membranes prepared by dip-coating method

PFSA-TiO₂(or Al₂O₃)-PVA/PVA/PAN difunctional hollow fiber composite membranes with separation performance and catalytic activity have been prepared by dip-coating method. The good separation performance was brought about by the glutaraldehyde (GA) surface cross-linked PVA/PAN composite membrane, and the good catalytic activity of the membrane was achieved by the perfluorosulphonic acid (PFSA) used. The difunctional hollow fiber membranes were characterized by XRD, TGA, EDX, SEM, and FTIR. The separation performance was measured by dehydration of azeotropic top product of ethanol-acetic acid esterification, and the catalytic activity was obtained by investigating the esterification of ethanol and acetic acid. The FTIR spectra and the morphologies of difunctional hollow fiber composite membranes were similar for samples prior to esterification and post-esterification with ethanol and acetic acid for 24?h. Difunctional hollow fiber composite membranes with 2% PFSA, 8% TiO₂ (named as DM-T1), and 2% PFSA, 8% Al₂O₃ (named as DM-A1) (all by weights) showed the best catalytic activity. They displayed fluxes of 165 and 173?g/m^2?h, separation factors of water to ethanol of 279 and 161, PFSA contents in difunctional hollow fiber composite membrane of 3.2 and 2.4%, the ratios of PFSA to feed solution (acetic acid?Cethanol) of 0.031 and 0.023%, and the equilibrium conversion of ethanol at 53.5 and 57.6%, in the given order for TiO₂ and Al₂O₃ containing samples.     

Pervaporation separation of binary organic–aqueous liquid mixtures using crosslinked PVA membranes. III. Ethanol–water mixtures

The application of the pervaporation process in biotechnology is rapidly growing. A two stage pervaporation process could be applied to the downstream processing of ethanol fermentation. In this paper, the second stage process—a water-selective process—was investigated in detail using the crosslinked poly(vinyl alcohol) membranes with the low molecular weight of poly(acrylic acid) as the crosslinking agent. The ratio of poly(vinyl alcohol) and poly(acrylic acid) in the membrane was 90/10, 85/15, and 80/20 by weight. The prepared membranes were tested to separate the various compositions of the water–ethanol mixtures, specially 50/50 solution at 60°C and 30/70, 20/80, 10/90, and 4.4/95.6 solutions at 60, 70, and 75°C. For water: ethanol = 50 : 50 solution, the separation factor α_w/e = 260 at 75°C was obtained by using a PVA/PAA = 80/20 membrane. The permeation rate and the separation factor at the azeotropic point of a water–ethanol mixture showed 30 g/m²/h and 5800 at 75°C, respectively, when a PVA/PAA = 80/20 membranes was used. © 1995 John Wiley & Sons, Inc.     

Tubular composite PVA ceramic supported membrane for bio-ethanol production

Thin polyvinyl alcohol (PVA) layers loaded with fumed silica were coated on porous ceramic supports. Scanning electron microscope (SEM) was used to characterize the ceramic-supported thin PVA active layers and the effects of coating gel PVA concentration on thickness and density of the active layers were investigated. Pervaporation (PV) dehydration of 90 wt.% ethanol was performed at temperatures of 30, 45 and 60 °C. The values of water flux (0.05–2.92 kg/m² h) and selectivity (3–180) exceed typical values obtained for pure PVA membranes. Besides the pervaporation separation index (PSI) varies from 5.84 to 82.81. Compared to pure PVA membrane with maximum PSI of 47.2, the pervaporation performance was significantly improved. The best separation performance was obtained using the membrane prepared from 5 wt.% PVA solution containing 6 wt.% fumed silica and at pervaporation temperature of 45 °C with permeation flux of 1.69 kg/m² h, and selectivity of 50. The highest permeation flux, selectivity and PSI was 2.92 kg/m² h, 180 and 82.81, obtained at 60, 30 and 45 °C, respectively, while using membranes loaded with 8, zero and 6 wt.% of fumed silica in PVA membrane prepared from 5, 10 and 5 wt.% PVA solutions, respectively. The novel ceramic support increased mechanical strength of the membrane and protected the ultrathin polymeric top active layer under aggressive operating conditions, especially high pressure gradient across the membrane. Incorporation of fumed silica also resulted in higher water permeation flux. Due to these results, the synthesized membranes are suitable for ethanol purification in industrial scales.     

Improved proton conductivity and methanol permeability of PVA-based proton exchange membranes using diphenylamine-4-sulfonic acid sodium salt and silica nanoparticles

ABSTRACT

A novel series of PVA/DPA-4-SASS/SiO₂ composite membranes were fabricated and characterized in the present study. Compared to the neat PVA, water uptake, proton conductivity, and ion exchange capacity of the membranes were enhanced. The membrane containing 5 Wt. % of SiO₂ nanoparticles and 80 Wt. % of the DPA-4-SASS showed the highest values of water uptake, proton conductivity (1.5 × 10^?1 S/cm) and ion exchange capacity (1.47 mmol/g). The results also indicated that methanol permeability was decreased by increasing the DPA-4-SASS content in the hybrid membranes. Thermal stability and mechanical properties of the cross-linked membranes were also improved.     

Enhanced Conversion in the Direct Synthesis of Diethyl Carbonate from Ethanol and CO2 by Process Intensification

To overcome the low equilibrium conversion in the direct synthesis of diethyl carbonate from ethanol and CO₂ under moderate reaction conditions, the reaction was conducted in a membrane reactor packed with pelletized Cu‐Ni:3‐1 supported on activated carbon. A SiO₂/γ‐Al₂O₃ commercial membrane and zeolite A membranes synthesized on commercial Al₂O₃ supports were evaluated in the membrane reactor. Although characterization of the membranes by X‐ray diffraction confirmed the presence of a zeolite A layer on the supports, gas permeation and permselectivity tests of ethanol and water evidenced some defects of the synthesized membranes. An increase in conversion with respect to a conventional packed‐bed reactor was observed in the membrane reactors prepared on Al₂O₃, but equilibrium conversion was not attained. However, with the commercial membrane, the ethanol conversion was higher than the equilibrium conversion.     

Porous Ceramic Membranes: Preparation, Transport Properties and Applications

The preparation and characterization of porous ceramic membranes is presented. These membranes consist of a macroporous support system, with or without a mesoporous intermediate layer, and a microporous top layer. For the macroporous support membranes two manufacturing routes are described: a conventional and a RBAO (Reaction Bonded Aluminium Oxide) route. The mesoporous -Al₂O₃ layer is obtained by means of a sol-gel dipcoating technique. Three microporous top layers are considered: SiO₂, Al₂O₃-pillared montmorillonite and Laponite. These top layers have different pore structures which results in different gas transport properties. A SiO₂ membrane can be used for H₂ removal from a gas mixture. Al₂O₃-pillared montmorillonite and Laponite membranes do not show specific gas separation properties. Dehydration of water/2-propanol mixtures by means of pervaporation also proved a different behavior for these microporous membranes.     

Pervaporation of methanol/dimethyl carbonate using SiO2 membranes with nano‐tuned pore sizes and surface chemistry

Porous silica membranes with different pore sizes (average pore size: 0.3–1.2 nm) and surface chemistry were prepared from SiO₂, steam‐treated SiO₂, SiO₂? ZrO₂, and SiO₂? TiO₂ by sol‐gel processing, and were applied to the pervaporation (PV) separation of methanol (MeOH) /dimethyl carbonate (DMC) mixtures at 50°C. Although SiO₂? ZrO₂ membranes demonstrated a separation factor of <10, the SiO₂ porous membranes had an increased separation factor from 10–160. Silica membranes with an average pore size of 0.3 nm showed the highest permselectivity of methanol with a separation factor of 140 and a methanol flux of 180 mol/(m²h) for MeOH 50 mol% at 50°C. To characterize the surface property of SiO₂ membranes, SiO₂ powdered samples were used for an adsorption experiment of vapor (MeOH, DMC) in single and mixed systems, revealing increased MeOH selective adsorption for SiO₂ powders with hydrophilic and small pores, which was consistent with PV performance. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Inorganic nanoparticles incorporated in polyacrylonitrile-based mixed matrix membranes for hydrophilic,ultrafast, and fouling-resistant ultrafiltration

Mixed matrix membrane (MMM) structures and performances are greatly affected by the distribution of nanoparticles in the polymeric matrix. Until now, there has been little research on the effects of nanoparticle distribution states on polyacrylonitrile (PAN)-based MMM structures and performances. In this paper, different intermolecular interactions between nanoparticles and PAN molecules were generated by in situ fabricated amino-functionalized SiO₂ and TiO₂ nanoparticles to create absolutely different distribution states of nanoparticles in a PAN matrix. The results indicated that, due to the strong interactions between amino and cyano groups, SiO₂ is distributed in the PAN membranes homogeneously, while most of the TiO₂ migrates to the membrane's top surfaces or the walls of pores or even escape from the membranes during the nonsolvent index phase separation (NIPS) process. PAN-TiO₂ MMMs have more hydrophilic top surfaces, higher porosity, larger mean pore size, and stronger antifouling performances than pure PAN and PAN-SiO₂ membranes. The PAN-TiO₂ MMMs have an ultrahigh water flux of 1204.6 L/(m² h), which is more than 44 times that of PAN membranes. And the good pore structures and hydrophilicity of the membranes derived from special interactions between in situ TiO₂ nanoparticles and PAN molecules can give high-performance PAN-based ultrafiltration membranes a bright future. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47902.