Porous Polysulfone Support Research Articles

Characterization and Evaluation of Reverse Osmosis Membranes Modified with Ag2O Nanoparticles to Improve Performance.

The objective of this work was to prepare and characterize a new and highly efficient modified membrane by in situ interfacial polymerization on porous polysulfone supports. The process used m-phenylenediamine and trimesoyl chloride in hexane, incorporating silver oxide Ag2O nanoparticles of varied concentrations from 0.001 to 0.1 wt%. Ag2O nanoparticles were prepared at different sizes varying between 20 and 50 nm. The modified membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), transmission electron microscopy (TEM), and contact angle measurement. The results showed a smooth membrane surface and average surface roughness from 31 to 74 nm. Moreover, hydrophilicity improved and the contact angle decreased to 41° at 0.009 wt% silver oxide. The performances of the developed membranes were investigated by measuring permeate fluxes and salt rejection capability by passing NaCl solutions (2000 ppm) through the membranes at 225 psi. The results showed that the flux increased from 26 to 40.5 L/m2 h, while the salt rejection was high, at 99 %, with 0.003 wt% Ag2O nanoparticles.

Effect of iron oxide nanoparticles on the performance of polyamide membrane for ground water purification

Maghemite iron oxide nanoparticles (γ-Fe2O3) with a size of about 10nm have been successfully incorporated in mixed matrix reverse osmosis membranes based on interfacial polymerization (IP) of thin film nanocomposite (TFNC) on porous polysulfone supports. TFNC elaborated in this study comprise iron oxide nanoparticles (NPs), with different concentrations varying from 0.1 to 0.9wt%, dispersed in polyamide host matrix. The performances of the obtained TFNC were evaluated based on the water permeability and salt rejection. Results indicated that the NPs improved membrane performance under optimal NP concentration. By changing the content of the filler, better hydrophilicity was obtained; the contact angle was decreased from 74° to 29°. Also, with initial NaCl concentration of 2000ppm and under pressure of 225psi, the permeate water flux increased from 26 to 44L/m2h at NPs concentration of 0.3% with the maintaining of high salt rejection of 98%.

Synthesis and characterization of polyamide thin-film nanocomposite membrane reached by aluminum doped ZnO nanoparticles

We report in this study the synthesis of mixed matrix reverse osmosis membranes by interfacial polymerization (IP) of thin film nanocomposite (TFNC) on porous polysulfone supports (PS). This paper investigates the synthesis of aluminum doped ZnO nanoparticles (NPs) using the sol–gel processing technique and evaluates the performance of mixed matrix membranes reached by these semiconducting NPs. Aqueous m-phenyl diamine (MPD) and organic trimesoyl chloride (TMC)-NPs mixture solutions were used in the IP process. The reaction of MPD and TMC at the interface of PS substrates resulted in the formation of the thin film composite (TFC). NPs of Al-doped ZnO with a size of about 25nm were used for the fabrication of the TFNC membranes. These membranes were characterized and evaluated in comparison with the neat TFC ones. Their performances were evaluated based on the water permeability and salt rejection. Experimental results indicated that the NPs improved membrane performance under optimal concentration of NPs. By changing the content of the filler, better hydrophilicity was obtained; the contact angle was decreased from 74° to 13°. Also, the permeate water flux was increased from 26 to 32L/m2h when the content of NPs is 0.5 (wt%) with the maintaining of high salt rejection of 98%.

Synthesis and characterization of polyamide thin-film nanocomposite membrane containing ZnO nanoparticles

We report in this study the synthesis of mixed matrix reverse osmosis membranes by interfacial polymerization (IP) of thin film nanocomposite (TFNC) on porous polysulfone supports (PS). This paper investigates the synthesis of ZnO nanoparticles (NPs) using the sol-gel processing technique and evaluates the performance of mixed matrix membranes reached by these aerogel NPs. Aqueous m-phenyl diamine (MPD) and organic trimesoyl chloride (TMC)-NPs mixture solutions were used in the IP process. The reaction of MPD and TMC at the interface of PS substrates resulted in the formation of the thin film composite (TFC). NPs of ZnO with a size of about 25 nm were used for the fabrication of the TFNC membranes. These membranes were characterized and evaluated in comparison with neat TFC ones. Their performances were evaluated based on the water permeability and salt rejection. Experimental results indicated that the NPs improved membrane performance under optimal concentration of NPs. By changing the content of the filler, better hydrophilicity was obtained; the contact angle was decreased from 74° to 32°. Also, the permeate water flux was increased from 26 to 49 L/m2.h when the content of NPs is 0.1 (wt.%) with the maintaining of lower salt passage of 1%.

Enhanced Performance of a Novel Polyvinyl Amine/Chitosan/Graphene Oxide Mixed Matrix Membrane for CO2 Capture

In this study, a facilitated transport mixed matrix membrane was fabricated by a surface coating method. Polyvinyl amine (PVAm) and chitosan (Cs) were used as the polymer matrix materials and coated onto a porous polysulfone (PS) support. Graphene oxide (GO) grafted with hyperbranched polyethylenimine (HPEI-GO) was added as the nanofiller. The gas separation tests with CO2/N2 (10:90 v:v) mixed gas suggest that the addition of GO could improve CO2/N2 selectivity. The highest CO2 permeance was 36 GPU in the membrane with 2.0 wt % HPEI-GO, and the optimal selectivity was 107 in the membrane with 3.0 wt % HPEI-GO. Herein, GO could provide a transport channel for CO2 and enhance the long-term stability of the membranes. Further gas separation tests under various relative humidities confirmed that facilitated transport was the main mechanism of gas separation through the membrane. The stability test suggests that the membrane has long-term stability. CO2 transports through the membrane mainly by the facilitated...

Membranes: Chlorine Resistant Glutaraldehyde Crosslinked Polyelectrolyte Multilayer Membranes for Desalination (Adv. Mater. 17/2015)

Novel membranes are fabricated for use in desalination and water purification applications by F. Caruso, S. E. Kentish, and co-workers, described on page 2791. The crosslinked polyelectrolyte multilayer membranes are synthesized on a porous polysulfone support within aqueous media and are crosslinked with glutaraldehyde. This leads to NaCl rejections of up to 97%. The incorporation of a highly sulfonated polysulfone polyanion results in outstanding chlorine resistance.

Cetyltrimethylammonium bromide–silica membrane for seawater desalination through pervaporation

A simple preparation of mesostructured cetyltrimethylammonium bromide (CTAB)–silica membrane is reported. It effectively desalinates seawater to pure water through pervaporation separation process. The membrane thickness was of nanometer-length-scale obtained by deposition of CTAB–silica colloids on porous polysulfone support. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM) studies were performed to characterize the membrane while the structure of the colloids in coating solution was probed by small-angle neutron scattering (SANS). The prepared membranes exhibited excellent salt rejection efficiency of 99.9% in desalination of synthetic seawater of 40,000 ppm NaCl by pervaporation at 25∘C. The pure water flux was in the range of 1–2.6 kg m−2 h depending upon the membrane configuration and thickness. The flux could be greatly enhanced by operating the process at higher temperatures of 40–80∘C but it was at the cost of decreased salt-rejection efficiency. The initial rejection efficiency and flux of the membrane was found to be restored upon cooling the membrane back to room temperature.

Fabrication of polyamide membrane reached by MgTiO3 nanoparticles for ground water purification

Here, we report the fabrication of mixed matrix reverse osmosis membranes by interfacial polymerization (IP) of nanocomposite on porous polysulfone supports. Nanocomposites elaborated for this study comprise magnesium titanium oxide (MgTiO3) nanoparticles dispersed in polyamide host matrix synthesized by the in situ IP process on porous polysulfone commercial supports. Aqueous m-phenyl diamine and organic trimesoyl chloride nanoparticles mixture solutions were used in the IP process. Nanoparticles of MgTiO3 with a size of about 80nm were used as filler for the fabrication of the nanocomposite membranes with a concentrations varying from 0.0001 to 0.009 wt.%. The samples were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, and contact angle setup. Their performances were evaluated based on the water permeability and salt rejection. Results indicated that the nanoparticles are well dispersed in the host matrix of polyamide layer and improved membrane performance under optimal nanoparticle content. By changing the concentration of the filler, hydrophilicity and roughness of the nanocomposite membranes were increased. Notably, the permeate water flux increased from 26 to 44.6 L/m2 h at the nanoparticles concentration of 0.001% with the maintaining of high salt rejection of 98%. These results were obtained with initial NaCl concentration of 2,000 ppm and under pressure of 225 psi. Also better hydrophilicity was obtained; the contact angle was decreased from 73 to 24°.

Preparation and properties of novel pH-stable TFC membrane based on organic–inorganic hybrid composite materials for nanofiltration

A series of thin-film composite nanofiltration membranes have been fabricated by coating the poly(vinyl alcohol) and 3-mercaptopropyltriethoxysilane aqueous solution prepared by a sol–gel process on porous polysulfone support, followed by thermal cross-linking treatment. In order to improve the hydrophilicity of the nanofiltration membranes, the –SH in the membranes are oxidized into –SO3H by immersing the membranes in H2O2 aqueous solution. Notably, no organic solvent is used during the membrane preparation, showing enough green chemistry technology for environmental protection. The properties of the composite nanofiltration membranes are characterized by ATR-FTIR, SEM, AFM and static contact angle. The optimal composite nanofiltration membrane (PVA-SMPTES-0.6) developed exhibits a rejection of 98.0% and a water flux of 43.3Lm−2h−1 for a feed containing 2000mgL−1 Na2SO4 at 2.0MPa. Furthermore, no irreversible changes in membrane performance have been observed after prolonged exposure (up to 30 days) of PVA-SMPTES-0.6 membrane to extreme acid or alkali aqueous solution.

Synthesis and characterization of a layered-hybrid membrane consisting of an organosilica separation layer on a polymeric nanofiltration membrane

In this study a new type of layered hybrid membrane was fabricated. This new membrane consisted of a thin organically bridged silica separation layer deposited onto the surface of a flexible polymeric membrane, NTR-7450 (Nitto Denko, Japan), and was comprised of a sulfonated polyethersulfone top layer and a porous polysulfone support. Using 1,2-bis(triethoxysilyl)ethane (BTESE) as a precursor, a continuous and defect-free BTESE separation layer was deposited onto the surface of a polymeric nanofiltration membrane via a facile, reproducible and scalable sol–gel spin-coating and low-temperature curing process. First, the optimal preparation conditions were established, which included the curing temperature and the spin-coating cycles. The membranes were then used for the vapor permeation dehydration of isopropanol-water solutions, and showed a stable water flux of 2.3kg/(m2h) and an improved separation factor of about 2500, which was an increase of approximately 5-fold compared with that of a polymeric nanofiltration membrane. In addition, single-gas permeance through this membrane was also discussed and a modest H2/N2 selectivity of 26 was obtained, which approximated the performance of ceramic-supported BTESE-derived silica membranes.

Thin-film composite membranes formed by interfacial polymerization with natural material sericin and trimesoyl chloride for nanofiltration

Novel flat-sheet thin-film composite membranes for nanofiltration were fabricated through interfacial polymerization of natural polymer sericin and trimesoyl chloride (TMC) on porous polysulfone support membrane. The preparation parameters including pH of aqueous phase, reaction time, curing temperature, curing time, sericin content and TMC concentration were investigated. The properties of the resultant membrane were characterized in terms of surface chemical structure, morphological structure, surface zeta potential, pure water flux, molecular weight cut-off (MWCO), pore size and rejections to different solutes including electrolytes and organic anionic dyes. It was found that the obtained sericin–TMC composite membranes had smooth and amphoteric surfaces with an isoelectric point at pH about 4.1. The membrane with a MWCO of 880g/mol had a pure water permeability of 11.9l/m2hbar and exhibited a salt rejection order of MgCl2 (22.5%)<MgSO4 (40.5%)≈NaCl (40.8%)<Na2SO4 (95.4%) at neutral pH. The dye removal tests indicated that the obtained membrane could effectively reject the organic anionic dyes at neutral pH with good anti-fouling property, especially for the dyes with relatively higher molecular weight and/or more negative charge. Moreover, compared with the commercial nanofiltration membrane NF270, the developed sericin–TMC composite nanofiltration membrane possessed better antifouling property.

Fabrication of a layered hybrid membrane using an organosilica separation layer on a porous polysulfone support, and the application to vapor permeation

Using 1,2-bis(triethoxysilyl)ethane (BTESE) as a single precursor, a uniform, defect-free and perm-selective organosilica layer was successfully deposited onto porous polysulfone ultrafiltration (PSF-UF) supports via a simple sol–gel spin-coating and thermal-treatment process. The layered hybrid membranes, where BTESE-derived SiO2 is deposited on polymer supports, were applied to the vapor permeation dehydration of isopropanol–water (90/10wt%) solutions at 105°C, and demonstrated a water flux of 1.6kg/m2h and a separation factor of 315 with no selectivity for a PSF-UF support. Long-term stability testing of vapor permeation also confirmed the excellent stability of these BTESE/PSF-UF layered hybrid membranes. Moreover, compared with porous PSF-UF supports, this layered hybrid membrane also showed improved gas separation performance and a moderate (≈10) separation factor for H2/N2.

Highly chlorine-resistant multilayer reverse osmosis membranes based on sulfonated poly(arylene ether sulfone) and poly(vinyl alcohol)

Sulfonated cardo poly(arylene ether sulfone) copolymers (SPAES-C) were synthesized via post-sulfonation of the parent polymer. A series of reverse osmosis composite membranes were obtained by coating SPAES-C on porous polysulfone support membranes, with varying the concentration of coating solutions. The SEM results indicated that the obtained reverse osmosis membranes had smooth surface, and no defect was observed. Meanwhile, the functional layer thickness obtained from the SEM results was in the range from 300 to 400nm. All the resulting membranes showed good water flux and appropriate NaCl rejection. In order to improve the NaCl rejection, a secondary layer of formaldehyde-cross-linked polyvinyl alcohol was coated on the surface of SPAES-C membrane, and this layer could improve NaCl rejection from 91.2% to 96.8% without a serious loss of water permeability. Compared with commercial PA reverse osmosis membrane, the composite membranes based on SPAES-C showed excellent chlorine-tolerance in reverse osmosis operation.

Effect of Cross-Linking Agent Chemistry and Coating Conditions on Physical, Chemical, and Separation Properties of PVA-Psf Composite Membranes

Composite nanofiltration membranes were formed by depositing ultra-thin, cross-linked polyvinyl alcohol (PVA) film on porous polysulfone (PSf) support membranes following a three step dip-coating procedure. The PVA coating films were cross-linked with aliphatic tricarboxylic acids (cis-/trans-aconitic) and aromatic dicarboxylic acids (phthalic, isophthalic, and terephthalic). Tricarboxylic acid cross-linked PVA was less crystalline and slightly more hydrophilic relative to PVA films cross-linked by aromatic dicarboxylic acids suggesting that the tricarboxylic acids are more effective is disrupting PVA crystallinity than the dicarboxylic acids. Cross-linked PVA-PSf composite membranes rejected NaCl and MgSO4 in the order: trans-aconitic acid < cis-aconitic acid < terephthalic acid < isophthalic acid < phthalic acid.

Enhanced desalination performance of polyamide bi-layer membranes prepared by sequential interfacial polymerization

A novel thin film composite (TFC) membrane featuring a polyamide bilayer was prepared on a porous polysulfone support using sequential interfacial polymerization. A conventional polyamide membrane prepared using m-phenylenediamine (MPD) in water and trimesoyl chloride (TMC) in hexane via interfacial polymerization was subsequently immersed into an alkaline aqueous solution of a hexafluoroalcohol (HFA)-containing aromatic diamine (HFA-MDA) to form an HFA-substituted aromatic polyamide layer (HFAPA) on the surface of the conventional (or reference) polyamide layer (REFPA). Water contact angle (θw) measurements indicated that the surface of the membrane becomes much more hydrophobic (θw≅140°) after forming the additional HFAPA layer onto REFPA (θw≅78°) although cross-sectional TEM images showed no significant increment in film thickness. The HFAPA-on-REFPA bilayer membrane, which features a more hydrophobic surface than the conventional REFPA membrane, exhibited improved salt rejection (ca. 50% reduction in salt passage) with a small loss in water flux (ca. 8% reduction) compared to the REFPA membrane, resulting in an excellent combination of salt rejection and water flux. Moreover, higher boron rejection was also achieved using the bilayer membrane (HFAPA-on-REFPA) compared to the REFPA membrane.

Thin-film composite nanofiltration membranes with improved acid stability prepared from naphthalene-1,3,6-trisulfonylchloride (NTSC) and trimesoyl chloride (TMC)

Thin-film composite (TFC) nanofiltration (NF) membranes with improved acid stability were fabricated through the interfacial polymerization of trimesoyl chloride (TMC) naphthalene-1,3,6-trisulfonylchloride (NTSC), and piperazine (PIP) on a porous polysulfone support membrane by varying the NTSC content in TMC-organic solution. The physico-chemical characteristics of the membranes were analyzed by ATR-FTIR, streaming potential measurement and surface contact angle measurement, the permeation properties were evaluated through cross-flow permeation tests, and the acid stability was investigated through both static acid soaking tests and long-term permeation tests under acidic condition. It was found that, as the NTSC content in TMC-organic solution increased, the membrane surface became more hydrophilic and negatively charged, the pure water permeability and molecular weight cut-off of the formed NF membrane increased from 5.5 to 10.6l/m2hbar and about 360 to 660Da, respectively, while the rejection rate to Na2SO4 firstly increased from 98.2 to 98.7% and then declined to a lower value of 97.8%. After soaking in 8w/v% H2SO4 for 30days or filtration with 4.9w/v% H2SO4 for 60days, the TFC membranes prepared from TMC and NTSC showed little performance change, while serious performance deterioration occurred with the TFC membrane prepared from TMC.

Acid stable thin-film composite membrane for nanofiltration prepared from naphthalene-1,3,6-trisulfonylchloride (NTSC) and piperazine (PIP)

Abstract Acid stable thin-film composite membrane for nanofiltration was fabricated by interfacial polymerization of naphthalene-1,3,6-trisulfonylchloride (NTSC) and piperazine (PIP) on porous polysulfone support membrane. The performance of the membrane was optimized by studying the preparation parameters including monomer content, reaction temperature and additive in organic phase. The separation performance of the resultant membrane was evaluated through permeation experiments, the membrane property was characterized by ATR-FTIR, XPS AFM, SEM and streaming potential measurements, and the acid stability was investigated through both static acid soaking tests and long-term permeation tests under acidic condition. After exposure to 20%(w/v) H2SO4 for 2 months or running with 4.9%(w/v) H2SO4 for 60 day, the PIP-NTSC composite membrane showed minor change in separation performance and no evident chemical change in the active skin layer, indicating that the developed membrane possessed good acid stability. The desired membrane exhibited a pure water permeability of about 5.8 l/m2 h bar, a MWCO of as high as 5000 Da, and an attractive solute rejection of higher than 86.5% for a feed containing 500 mg/l Na2SO4 at 0.5 MPa. Furthermore, the PIP-NTSC composite membrane could be used to treat acidic effluents from metal industries with good perm-selectivity and long-term stability.

Disulfonated poly(arylene ether sulfone) random copolymer thin film composite membrane fabricated using a benign solvent for reverse osmosis applications

High performance thin film composite (TFC) membranes for reverse osmosis applications were fabricated by coating solutions of highly chlorine-tolerant disulfonated directly copolymerized poly(arylene ether sulfone) random copolymers (BPS-XX, e.g., BPS-20 and 32) on a commercially available porous polysulfone ( e.g., Udel ®) support. Solvents used in the formation of the TFCs must dissolve the sulfonated polysulfones used as the skin materials, while not harming the non-sulfonated polysulfone support membrane. For this purpose, environmentally friendly solvents were selected via a systematic screening process using a triangular solubility diagram. However, these benign solvents [ e.g., di(ethylene glycol)] generally have high boiling points (>∼190 °C). Thus, they necessitate the use of a special TFC formation process, since solvent evaporation at high temperatures caused pore shrinkage in the polysulfone support membrane and could lead to a catastrophic decrease in membrane water permeance. Support membranes were initially immersed in an IPA/glycerin mixture, after which the IPA was allowed to evaporate, leaving glycerin within the membrane pore structure. After a repeated coating procedure using dilute BPS-XX solutions, the TFC membranes were dried under vacuum at elevated temperatures. During this process, the glycerin reduced pore penetration of BPS-XX and prevented pore collapse during the drying procedures. Finally, water-miscible glycerin was eliminated via water treatment. The newly developed coating method formed ultra-thin and defect-free BPS-XX layers on a micro-porous Udel ® support membrane. For example, BPS-32 TFC membranes showed NaCl rejection (∼97%), similar to that of its dense membranes. Furthermore, decreasing the amount of coating solution and, therefore, the BPS-32 coating thickness, resulted in improved pure water flux. The TFC water flux was further improved and was accompanied by small reduction in salt rejection after various TFC membrane treatments ( e.g., in situ acidification or IPA treatment).

Thin film composite reverse osmosis membrane development and scale up at CSMCRI, Bhavnagar

Thin film composite (TFC) reverse osmosis membrane containing polyamide active layer on porous polysulfone support was developed at the scale of 1 m width × 100 m long in a batch using semi-automated mechanical casting and coating machines. The polysulfone support was made according to phase inversion method at the rate of 3−6 m/min., and the polyamide active layer on the polysulfone support was prepared by interfacial polymerization method at the rate of 0.3−0.5 m/min under different conditions. Since desalination of brackish water does not require the membrane with very high salt rejection efficiency, emphasis was placed on increase in the flux while maintaining the salt rejection at 94 ± 2%. The membrane preparation conditions and structure−performance relationships were correlated by different techniques like porometry, infrared spectra, scanning electron microscopy and atomic force microscopy. The TFC membranes exhibited 94−96% salt rejection with water flux of 50−65 L/m 2.h when tested with 5000−1500 ppm salt solution at 250 psi. Surface modification of the TFC membrane with polymers containing hydrophilic groups was carried out to impart fouling resistance. Spiral modules of 4040 and 8040 size were made and tested them extensively in the field conditions in 500−2000 LPH brackish and sea water desalination plants.

A novel sulfonated poly(arylene ether ketone) reverse osmosis membrane: Effect of casting condition on separation characteristics

A novel sulfonated poly(arylene ether ketone) (sPAEK) reverse osmosis (RO) membrane was prepared. This sPAEK is composed of a mechanically strong hydrophobic group and an anionic hydrophilic group wherein water is soluble. Since this poly(arylene ether ketone) showed a high chlorine resistance, it could be one of the candidate materials for a practical desalination RO. After this polymer was coated on a porous polysulfone support, a post-treatment was carried out to densify the morphology of the separating layer. It was investigated how the coating condition can affect the separation phenomena in terms of a water flux and a rejection of salts. As the weight% of sPAEK increased, the water flux decreased and the salt rejection increased. A post-treatment of the RO membrane significantly improved the separation characteristics.