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Pervaporation membranes made from polyethersulfone (PESU), polyphenylsulfone (PPSU), polytrimethylphenylethersulfone (T-PESU) and hydrophilic PESU-co-Pluronic (H-PESU) polymers were evaluated for dehydration of ethanol and methanol. Fundamental characteristics of pore structure, free volume, d-spacing, water contact angle, water and ethanol uptakes were investigated and correlated with their dehydration performance. The H-PESU membrane shows the best ethanol dehydration performance due to its synergetic combination of the strengths from both rigid hydrophobic PESU and flexible hydrophilic Pluronic moieties. It has the highest water permeability of 0.322 mg m −1  h −1  kPa −1 which is 2–6 times higher than other three membranes because the hydrophilic Pluronic moiety may form special water transport channels. It also has a comparable mole-based selectivity of 685 due to the rigid hydrophobic PESU moiety that prevents the membrane from uncontrolled swelling. Long-term tests evidence the operating stability of both H-PESU and PESU membranes. In addition, the methanol dehydration performance of these membranes is superior to the other reported polymeric membranes. The water in the permeate can be concentrated to 86.8%. These promising preliminary results suggest that these polyarylether (PAE) membranes have great potential for ethanol and methanol dehydration. [ABSTRACT FROM AUTHOR]

The decontamination of selenium (Se) and arsenic (As) from aqueous environments has been an emerging area for membrane technology. They are difficult to be removed because of various oxidation states, range of toxicity and solubility. In this work, three water stable zirconium metal-organic framework (MOF) UiO-66 nanoparticles with different diameters, i.e., 30, 100 and 500 nm, have been synthesized and incorporated into the selective layer to form thin-film nanocomposite (TFN) membranes. These membranes were tailored to remove the Se and As concurrently. Comparing to the thin-film composite (TFC) membranes, the TFN membranes exhibit higher pure water permeability (PWP) and rejections for both pollutants due to their smaller pore size and higher hydrophilicity. In addition, the TFN membrane comprising 30 nm UiO-66 has the best performance among the three TFN membranes. The effects of particle loading have also been investigated for the 30 nm UiO-66 TFN membranes. The TFN membrane containing 0.15 wt% UiO-66 has the highest PWP of 11.5 LMH/bar and remarkable rejections of 96.5%, 97.4% and 98.6% toward SeO 3 2- , SeO 4 2- and HAsO 4 2- , respectively. Higher rejections are also achieved in the concurrent removal of Se and As. Additionally, the TFN membrane exhibits robust long term stability. To our best knowledge, this is the first work to study the particle size and loading effects of UiO-66 particles in the selective layer of TFN membranes for Se and As removal. The results achieved in this work may provide promising insights for the development of next generation NF membranes with superior performance. [ABSTRACT FROM AUTHOR]

The removal of boron compounds from aqueous systems is receiving worldwide attention because boron contaminations in various water sources are rising in recent years. Boron toxicities to living beings and harmfulness to semi-conductor manufacturing are increasingly accessed and recognized by researchers. A wide range of technologies has been unveiled for boron removal. Among them, membrane technologies for boron removal have come to the scientific spotlight. Especially, some emerging membrane processes were devised recently, e.g. forward osmosis (FO), polymer enhanced ultrafiltration (PEUF), membrane adsorptive filtration (MAF), membrane distillation (MD), etc. Most of them were demonstrated with many competitive edges compared to the traditional methods. This review will present a comprehensive summary of the recent advances in membrane-based deboronation technologies from the perspectives of membrane materials, membrane fabrication and system design. Comparisons between various membrane processes and prospects of each technology will be covered. The information may provide inspiration for future researchers and pave the way to develop effective and efficient deboronation technologies for the years to come. [ABSTRACT FROM AUTHOR]

Thin film composite membranes (TFC) consisting of an ultra-thin polyamide layer made from interfacial polymerization remain to be of paramount importance for seawater desalination. Incorporation of nanoparticles into the polyamide layer has produced thin film nanocomposite (TFN) membranes with better performance than traditional TFC membranes. However, challenges of defect formation with the introduction of nanoparticles need careful adjustments in order to surpass the trade-off relationship between permeability and selectivity. Here, we explored the influential effects of nanoparticles, solvent and surfactant treatments on the desalination performance of TFN membranes under 55 bar using 35,000 ppm NaCl as the feed at 25 °C. TFN membranes with various loadings of polyhedral oligomeric silsesquioxane (POSS) and TiO 2 -SiO 2 core-shell nanoparticles were fabricated. Surfactant treatment was performed in two different ways: membrane soaking and in-tank addition. Unexpectedly, the latter endows the membrane with an improved rejection without sacrificing its flux possibly due to the formation of a surfactant monolayer to heal defects in TFN membranes. The newly developed TFN-T membrane with the aid of synergic effects from nanoparticles, ethanol and surfactant post-treatments shows comparable performance to most commercial membranes. This work may provide useful insights to overcome the trade-off relationship between permeability and selectivity of TFN membranes for seawater desalination. [ABSTRACT FROM AUTHOR]

Construction of PVDF hollow fiber membranes with antifouling lumen surfaces is of great interest and significance for many industrial applications because the inside-out filtration mode allows good control over module hydrodynamics. For the first time, a zwitterionic polymer was immobilized on the lumen surface of a PVDF hollow fiber membrane via thermal-induced graft copolymerization with an objective to render the PVDF membrane antifouling. The graft copolymerization consists of two steps: ozone-assisted surface pre-activation and grafting of sulfobetaine methacrylate (SBMA). The grafting density and chain length were systematically optimized by manipulating the operational parameters, e.g. ozone treatment and grafting duration. The resultant membranes were studied with respect to their structure, morphology, ultrafiltration (UF) performance, while their fouling behaviors were evaluated by flux recovery ratio and the resistance-in-series model. In comparison to the pristine one, the composite membranes exhibited superior fouling resistance for a 2-h filtration of a 2.0 wt% bovine serum albumin (BSA) solution. Especially, the irreversible fouling-induced resistance was prominently reduced from 53% to 15% due to the outstanding hydration capacity of the polySBMA polymer. Consequently, the flux recovery ratio ( FRR ) increased significantly from 47% to 85%, suggesting the promising prospect of the zwitterion-grafted PVDF hollow fiber membranes for their antifouling properties. Most importantly, the improvement in antifouling was achieved without sacrificing flux or rejection efficiency. This work may provide useful insights about lumen surface nano-structuring of the inner-selective hollow fiber membranes. [ABSTRACT FROM AUTHOR]

Herein, a novel nanocomposite organic solvent nanofiltration (OSN) membrane has been facilely fabricated by a highly-efficient one-step co-deposition of mussel-inspired catechol and octaammonium polyhedral oligomeric silsesquioxane (POSS-NH 3 + Cl - ) onto supports. The basic properties and morphologies of the co-deposited nanocomposite membranes were investigated with various physicochemical characterizations in detail. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra proved the present of POSS nanoparticles on membrane surface. X-ray photoelectron (XPS) results suggested the optimal ratio of POSS-NH 3 + Cl - and catechol for co-deposition. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images demonstrated the formation of a layer on support surface. The optimized nanocomposite membrane exhibited an ethanol (EtOH) permeance of 1.26 L m −2 h −1 bar −1 with a rejection of 99% to Rose Bengal (RB). The novel membrane also exhibited remarkable separation performance for dyes removal from a wide range of solvents including challenging polar aprotic and strongly swelling solvents. Particularly, the nanocomposite membrane demonstrated stable performances during a two-day long term test in DMF for RB concentration. In addition to providing a highly-efficient way to high-performance OSN membrane, this work may stimulate the bio-inspired design of advanced nanocomposite membranes for environmental applications. [ABSTRACT FROM AUTHOR]

Two hyperbranched polymers, hyperbranched polyglycidol (HPG) and 2, 3-Dihydroxypropyl-hyperbranched polyethylenimine (Diol-HPEI), were synthesized and studied as polychelatogens for boron reclamation via a hybrid ultrafiltration process, with the objectives of evaluating the key factors for polymer–boron chelation and improving boron rejection efficiency. Their chemical structures were unveiled by FTIR and XPS analyses whilst molecular weights were carefully tailored in order to be fully retained by a commercial ultrafiltration (UF) membrane. The chelation capacity of the two polymers was compared under different operating conditions i.e., chelating temperature, polymer loading and pH. It appears that Diol-HPEI prominently outperforms HPG because the tertiary amine group may be more competent than the ether group in terms of their protonation capability. Eventually, a rejection of 66–91% was achieved with a Diol-HPEI polymer loading of 100 g per g boron in the pH range of 6.9–9.0. Besides, the effects of interfering ions, i.e., Na + , Mg 2+ , Cl − and SO 4 2 - on polymer–boron interactions were examined in the Diol-HPEI/boron solution at the neutral condition. Results reveal that divalent cations may exert more negative influence on boron rejection owing to the competition between them and boron to form complexes with chelating polymers. These findings may provide useful insights in design of efficient boron-chelating polymers. [ABSTRACT FROM AUTHOR]

Low-molecular-weight poly(ethylene glycol) (PEG) is deliberately incorporated into synthesized swellable poly(ethylene oxide) (PEO) membranes via a facile post-treatment strategy. The membranes exhibit both larger fractional free volume (FFV) and a higher content of CO2-philic building units, resulting in significant increments in both CO2 permeability and CO2/H2 selectivity. The separation performance correlates nicely with the microstructure of the membranes. This study may provide useful insights in the formation and mass transport behavior of highly efficient polymeric membranes applicable to clean energy purification and CO2 capture, and possibly bridge the material-induced technology gap between academia and industry. [ABSTRACT FROM AUTHOR]

Abstract: Free-standing graphene oxide (GO) thin films have been assembled by a pressurized ultrafiltration method. The GO films exhibit a layered microstructure with high structural stability and hydrophilicity, as analyzed by XPS, FESEM, XRD, positron annihilation spectroscopy (PAS), etc. The effects of ultrafiltration pressure and feed composition on the film׳s microstructure and pervaporation performance for dehydration of ethanol were investigated and correlated with XRD and PAS observations. Experimental results suggest that the interlaminar spacing is determined by both packing density of GO nanosheets and water content in the feed solution. The packing density is sensitively affected by the ultrafiltration pressure applied during film formation. By tuning the ultrafiltration pressure, a high separation performance with water permeability of 13,800Barrer (1 Barrer=3.348×10− 19 kmol m m− 2 s− 1 Pa− 1) and water/ethanol selectivity of 227 is achieved for dehydration of an 85wt% ethanol aqueous solution at 24°C. Additionally, the total permeability varied from 50 to 113,000Barrer by increasing the water content in the feed from 0 to 100wt%. As a result, the ideal water/ethanol selectivity calculated from single-component feed tests is about 2260 which is much higher than the selectivity obtained from binary-component feed tests. This discrepancy is probably attributed to the effect of intermolecular hydrogen bonding between water molecules and the functional groups on GO nanosheets that enlarges the interlaminar spacing and allows more ethanol transport through the GO film. The interactions among the GO nanosheets and the feed components enable the film to effectively dehydrate ethanol via pervaporation. [Copyright &y& Elsevier]

Abstract: A dual-layer hollow fiber membrane consisting of copoly(1,5-naphthalene/3,5-benzoic acid-2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropanedimide) (6FDA-NDA/DABA)/polyhedral oligomeric silsesquioxane (POSS) as the outer functional layer and polyetherimide (Ultem®) as the inner support layer has been developed for ethanol hydration via pervaporation. By using lower dope flow rates and optimizing inner dope concentration, the newly developed hollow fiber membranes have desirable morphology consisting of a porous inner layer with low transport resistance and a macrovoid-free selective layer for a superior separation performance. Doppler broadening energy spectra (DBES) have been employed to analyze the depth profile of morphological evolution and examine the thickness of dense selective layer as a function of spinning conditions. Incorporating a small amount (2wt%) of POSS into the selective layer increases its free volume size and diffusion selectivity and hence improves the pervaporation performance of the hybrid membranes. The diffusion mechanism of permeate molecules through polymer chains containing POSS nanoparticles was proposed and verified via FTIR spectra, XRD curves, positron annihilation lifetime (PAL) characterization and vapor sorption tests. Compared to other hollow fiber membranes, the newly developed hollow fibers have a superior flux of 1.9kg/m2 h and a comparable separation factor of 166 for ethanol dehydration. The work may open up a new perspective for the development of next-generation high-performance dual-layer hollow fiber membranes with a POSS embedded selective layer for biofuel separation. [Copyright &y& Elsevier]

Nanofiltration (NF) membranes have been used previously for the recovery of dyes, salts, and water from textile wastewaters with high salinity. However, commercially available NF membranes have a high rejection for divalent salts (i.e., Na 2 SO 4 ), substantially reducing the salt recovery and membrane flux when treating textile wastewater containing Na 2 SO 4 . In this study, a tight ultrafiltration membrane (UH004, Microdyn-Nadir) was proposed to fractionate the dye and Na 2 SO 4 in the textile wastewater. The UH004 membrane with a molecular weight cutoff of 4700 Da provided complete passage of monovalent salts, with little rejection of Na 2 SO 4 . This significantly increases the filtrate flux that can be achieved with high-salinity wastewater since osmotic pressure and concentration polarization effects are minimized. Furthermore, the retention behavior of four different dyes was evaluated to determine the efficiency of this membrane process. This tight ultrafiltration membrane offered the high retention for direct dyes (i.e., direct red 80, direct red 23, and Congo red) and reactive blue 2. For instance, the UH004 membrane yielded >98.9% rejection for all of the dyes at a pressure of 4 bar even in the presence of 60 g L −1 Na 2 SO 4 . Subsequently, an ultrafiltration-diafiltration process was designed to separate a dye/Na 2 SO 4 aqueous mixture with 98% desalination efficiency and greater than 97% dye recovery after 5 diavolumes. These results clearly demonstrate that tight ultrafiltration membranes can be a stand-alone alternative to NF membranes for the effective fractionation of dye and Na 2 SO 4 in the direct treatment of high-salinity textile wastewater. [ABSTRACT FROM AUTHOR]

Pervaporation has been regarded as a promising separation technology in separating azeotropic mixtures, solutions with similar boiling points, thermally sensitive compounds, organic–organic mixtures as well as in removing dilute organics from aqueous solutions. As the pervaporation membrane is one of the crucial factors in determining the overall efficiency of the separation process, this article reviews the research and development (R&D) of polymeric pervaporation membranes from the perspective of membrane fabrication procedures and materials. [ABSTRACT FROM AUTHOR]