Polysulfone Support Membrane Research Articles

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).

Separation performance and interfacial properties of nanocomposite reverse osmosis membranes

Four different types of nanocomposite reverse osmosis (RO) membranes were formed by interfacial polymerization of either polyamide (PA) or zeolite A-polyamide nanocomposite (ZA-PA) thin films over either pure polysulfone (PSf) or zeolite A-polysulfone nanocomposite (ZA-PSf) support membranes cast by wet phase inversion. All three nanocomposite membranes exhibited superior separation performance and interfacial properties relative to hand-cast TFC analogs including: (1) smoother, more hydrophilic surfaces (2) higher water permeability and salt rejection, and (3) improved resistance to physical compaction. Less compaction occurred for membranes with nanoparticles embedded in interfacially polymerized coating films, which adds further proof that flux decline associated with physical compaction is influenced by coating film properties in addition to support membrane properties. The new classes of nanocomposite membrane materials continue to offer promise of further improved RO membranes for use in desalination and advanced water purification.

Novel tertiary amino containing thin film composite membranes prepared by interfacial polymerization for CO2 capture

A novel tertiary amine group containing fixed carrier thin film composite (TFC) membrane was developed by the interfacial polymerization of 3,3′-Diamino-N-methyldipropylamine (DNMDAm) and trimesoyl chloride (TMC) on the polysulfone (PS) support membrane. ATR-FTIR, XPS, AFM and SEM were employed to characterize the active surface of the composite membrane. The gas transport property of the DNMDAm-TMC/PS membrane was investigated by studying the permselectivity varying with feed gas pressure and the possible reactions between gases and the membrane. Furthermore, the effects of two important factors (the DNMDAm concentration and the TMC concentration) on membrane morphology and performance were investigated. It was found that both the DNMDAm concentration and the TMC concentration play important roles in determining the membrane morphology and performance, which may reconcile some contradictory findings in some references. Moreover, the DNMDAm-TMC/PS composite membrane showed both good CO 2 /N 2 and CO 2 /CH 4 separation performance. For CO 2 /N 2 gas mixture (20/80 by volume), the membrane prepared with 0.0062 mol/l of DNMDAm and 0.0226 mol/l of TMC displayed a CO 2 permeance of 173 GPU and CO 2 /N 2 selectivity of 70 at 0.11 MPa feed pressure. For CO 2 /CH 4 gas mixture (10/90 by volume), the same membrane showed a CO 2 permeance of 118 GPU and CO 2 /CH 4 selectivity of 37 at 0.11 MPa feed pressure. The high CO 2 /N 2 and CO 2 /CH 4 separation performance of DNMDAm-TMC/PS composite membrane was mainly attributed to the thin film thickness and the properties of tertiary amino groups.

Using nanocomposite materials technology to understand and control reverse osmosis membrane compaction

Composite reverse osmosis (RO) membranes were formed by interfacial polymerization of polyamide thin films over pure polysulfone and nanocomposite-polysulfone support membranes. Nanocomposite support membranes were formed from amorphous non-porous silica and crystalline microporous zeolite nanoparticles. For each hand-cast membrane, water flux and NaCl rejection were monitored over time at two different applied pressures. Nanocomposite-polysulfone supported RO membranes generally had higher initial permeability and experienced less flux decline due to compaction than pure polysulfone supported membranes. In addition, observed salt rejection tended to increase as flux declined from compaction. Cross-sectional SEM images verified significant reduction in thickness of pure polysulfone supports, whereas nanocomposites better resisted compaction due to enhanced mechanical stability imparted by the nanoparticles. A conceptual model was proposed to explain the mechanistic relationship between support membrane compaction and observed changes in water flux and salt rejection. As the support membrane compacts, skin layer pore constriction increased the effective path length for diffusion through the composite membranes, which reduced both water and salt permeability identically. However, experimental salt permeability tended to decline to a greater extent than water permeability; hence, the observed changes in flux and rejection might also be related to structural changes in the polyamide thin film.

Inorganic filler selection in PDMS membrane for acetone recovery and its application in a condenser-gas membrane system

PDMS mixed matrix membranes (MMMs) with inorganic fillers - TS720 and TS530 silica, NaY type zeolite and multiwalled carbon nanotube (MWCNT) - were prepared by solvent evaporation and then tested for pure gas (N 2 , O 2 ) and acetone/N 2 mixed gas permeability at various pressures at 35°C. The membranes were also tested for thermal stability. Results showed that the presence of the inorganic fillers improved the thermal stability of the PDMS membrane. Based on permeability and selectivity results, PDMS/TS720 MMM exhibited better performance, thus, it was chosen as the coating material in the fabrication of the thin film composite (TFC) membrane to be integrated into the condenser-gas membrane hybrid system. The TFC membrane was prepared by coating a thin layer of PDMS solution containing 20% (w/w) TS720 filler on the flat-sheet ultrafiltration polysulfone support membrane using a roller coating machine. Acetone/N 2 mixed gas permeation experiment was conducted at 35°C and 5 bars to ensure that the TFC membrane was defect-free. Results showed that the TFC membrane has an acetone permeance and selectivity of 964.3 GPU and 8.5, respectively. The condenser-membrane hybrid experiment was performed at various stage cuts (SCs) under controlled operating conditions (pressure, temperature, flow rate and acetone concentration). Results of the hybrid experiment showed an over-all acetone recovery as high as 91.9% at 60% SC.

Sulfonated poly(arylene ether sulfone) thin-film composite reverse osmosis membrane containing SiO2 nano-particles

Novel thin-film nano-composite membranes containing SiO2 nano-particles are successfully fabricated via interfacial polymerization with trimesoyl chloride (TMC), sulfonated poly(arylene ether sulfone) copolymers and silica (SiO2) nano-particles on a polysulfone (PS) support membrane. Sulfonated poly(arylene ether sulfone) copolymers containing carboxylic and amino groups (cPES) are successfully prepared via direct polymerization as novel thin-film composite (TFC) reverse osmosis (RO) membrane material. Mesoporous SiO2 nano-particles are also successfully synthesized. The synthesized cPES copolymers, SiO2 nano-particles and fabricated cPES membranes are characterized by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). The incorporation of SiO2 nanoparticles were confirmed by energy dispersive X-ray spectroscopy (EDX). Moreover, the effects of different fabrication conditions on performance are investigated. The cPES membrane with 1% (w/w) SiO2, which is cured at 70°C, exhibited the high salt rejection value (96.8%) with respect to NaCl and good water flux value (32 L/m2h).

Impacts of support membrane structure and chemistry on polyamide–polysulfone interfacial composite membranes

Herein, we discuss the properties of polyamide thin films formed via identical interfacial polymerization conditions over porous polysulfone supports with different physical and chemical properties. Polysulfone supports were formed by nonsolvent induced phase separation (i.e., immersion precipitation) employing several casting solution and precipitation bath chemistries. Hand-cast polysulfone films (and a commercial polysulfone membrane) exhibited a wide range of pure water permeabilities, dextran rejections, water contact angles, and surface roughness statistics. These results, combined with FTIR spectra and SEM images, confirm that each support offered a different skin layer pore morphology and chemistry. Polyamide composite membranes formed thereon displayed widely varying film morphology, separation performance, and interfacial properties. More permeable, hydrophilic supports produced low permeability polyamide–polysulfone interfacial composite membranes, whereas highly porous, relatively hydrophobic supports produced more permeable composite membranes. A conceptual model was proposed to explain the potential impacts of polysulfone support membrane properties during the polyamide interfacial polymerization reaction and the resulting characteristics of polyamide–polysulfone interfacial composite membranes.

Preparation of reverse osmosis composite membrane with high flux by interfacial polymerization of MPD and TMC

AbstractIn this study, reverse osmosis (RO) composite membrane with extra‐thin separation layer was prepared by the interfacial polymerization (IP) of metaphenylene diamine (MPD) with trimesoyl chloride (TMC) on the surface of polysulfone (PS) support membrane. The properties and structures of skin layer of RO composite membranes were characterized by FTIR and SEM, it was found that IP had occurred and the separation layer was formed. The effects of the monomer concentration on membrane flux and salt rejection were investigated, and the optimum concentration of MPD and TMC were 2 and 0.3% (w/v), respectively. To improve flux, the phase‐transfer catalyst was added to the water phase, and the effects were remarkable when the concentration of MPD was low, in which both salt rejection and flux increased by 20% than initial results. When some of the hydrophilic additives such as alcohols and phenols were added into water phase, the flux of the prepared membrane increased from 13.03 to 33.42 L/(m2 h) without loss in salt rejection. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Rejection properties of pesticides with a hollow fiber NF membrane (HNF-1)

NF membranes are potentially useful to remove residual hazardous organic pollutants such as pesticides and alkyl phthalates in drinking water treatment processes. In this study, the rejection properties of a hollow fiber NF membrane (HNF-1) for 8 kinds of pesticides were investigated using a bench scale cell: the membrane consisted of polyamide skin layer and polysulfone support membrane with a nominal desalting degree fo 35% at 0.3 MPa. In addition, hydrophilic organic compounds (molecular weight: 74.1–504.5), i.e. alcohols and saccharides, were also used as reference solutes. The hydrophilic compounds were rejected at rates of 9.0–97.8%, revealing that the molecular sieving effect was significant since the logarithm of solute permeability, log B, correlated linearly with the molecular width parameter, MWd, of the solute. Phenylic pesticides, such as alachlor, metolachlor, methoxychlor, and thiobencarb, were rejected at 88.7–99.3%. However, non-phenylic pesticides, such as aldicarb, simazine, atrazine, and pirimicarb, were rejected at lower degrees: 42.2–89.9%. The batch type sorption experiments indicated that all of the pesticides were adsorbed on the membrane, and the adsorption properties were controlled mainly by the hydrophobic property of the pesticides. Sorption properties based on solute recovery rates in the separation experiments, however, were different from those in the batch type experiments.

Recovery of anionic surfactant by RO process. Part II. Fabrication of thin film composite membranes by interfacial reaction

A new technique has been established to fabricate thin film composite membranes, by which a hydrophilic polymer could be coated in thin film on a hydrophobic support membrane. The new technique was composed of two steps: dispersion of a reactant to the hydrophilic polymer in the hydrophobic support membrane and interfacial reaction between the reactant and the hydrophilic polymer to produce thin film of the hydrophilic polymer on the support membrane. Composite membranes in which a thin film of sodium alginate is coated on a polysulfone support membrane were prepared by the new technique for the reverse osmosis separation of anionic surfactant–water mixture. Two methods were employed to fabricate a thin film of sodium alginate on the support membrane: (1) dispersion of the crosslinking agent, CaCl 2 alone in the support membrane and (2) dispersion of CaCl 2 in the support membrane with help of PVA which adheres fast to the support membrane. The formation mechanism of the thin layer was suggested schematically on each method. Both the methods could produce successively a thin layer of SA on the support membrane. Especially, method (2) gave a strong bonding of the thin layer on the support because of the large contact area with the support through the PVA layer which sticks fast to the SA layer. From the SEM pictures and permeation experiments, the method (2) was confirmed to be better to produce a defect-free thin film of SA on the support membrane.

Composite melamine-formaldehyde-furfuralcohol copolymerization membrane for reverse osmosis

The preparation and performance of the new composite reverse osmosis membrane were investigated. The ultrathin semipermeable barrier of the composite melamine-formaldehyde-furfuralcohol copolymerization membrane for reverse osmosis is formed on the porous surface of polysulfone support membrane by copolymerization between melamine-formaldehyde prepolymer and furfuralcohol under sulfuric acid catalyst. In the condition of operation pressure 20 kg/cm 2 and concentrated water flux 20 L/h, the membrane has 95% rejection and 0.3 m 3/m 2.d flux for 1500 ppm aqueous sodium chloride. The factors affecting the reverse osmosis performance of the composite membrane, such as amount of the prepolymer and catalyst, the temperature of the polymerization and the properties of additives etc, were investigated.

Investigation of performance of TMMA—FA composite membrane for reverse osmosis

The performance of the TMM-FA composite membrane for reverse osmosis was investigated. The ultrathin semipermeable barrier of the composite TMM-FA copolymerized membrane for reverse osmosis is formed on the porous surface of the polysulfone support membrane by copolymerization of TMM and FA with sulfuric acid as catalyst. At an operation pressure of 20 kg/cm 2 and a concentrated water flux fo 10 1/h, the membrane had 95.1% rejection and a flux of 0.27 m 3/m 2 d for 1500 ppm aqueous sodium chloride. The effect of concentration and pH values of the feed water on the membrane performance were investigated, and, at the same time, resistance to oxidation and chlorination, and stability during long operation were tested.