Poly membranes, supported

Ceramic tubing (inner diameter = 9 mm, outer diameter = 13 mm, pore size = 2.3 pm) was kindly provided by Kubota Co., Ltd., Japan, and used as the membrane support. The polymer latex containing poly-vinylydenchloride (PVdC) and poly-vinylchloride... 

Coating of ultrafiltration/microfiltration membrane supports such as polyvinylidene fluoride (PVDF) or polysulfone (PSF) with solutions of polymers such as poly(ether-hlocfc-amide) [51]. 

One of the most important degradation mechanisms of SLM is an emulsification ofthe membrane phase due to lateral shear forces. Therefore, formation of barrier layers on the membrane surface by physical deposition [98] or by interfacial polymerization could prevent instability [99, 100]. A polysulfone support with N-methylpyiTolidone as a solvent was coated by a poly(ether ketone) layer as the outside layer and gave a specific composite membrane support. Such composite hoUow-fiber membranes showed significant improvement in stabUity in copper ions permeation. 

Wieczorek, P., Tomaszewska, M. (1997). Transport ofamino acids through liquid membranes supported on novel poly(vinylidenefluoride) porous flat-sheet matrix. Solvent Extr. Ion. Exc., 15, 879-94. 

In a different approach based on membrane technology, oligomerization of ethene has also been examined using a poly(ethersulfone)-supported ionic liquid membrane containing [EMIMjCl-AlCh ionic liquids with or without the presence of [NiCl2 P(cyclohexyl)3]2 dimerization catalyst and dichloroethylaluminate as an acid scavenging co-catalyst [107]. 

MTR, Inc. has also developed another commercial PV application using silicon rubber coated on microporous poly-imide support membranes for the separation of dissolved volatile organic compound (VOC) from water, achieving very high separation factors for toluene, benzene, chlorinated solvents, esters, and ethers. 

Mohammad et al. [29] fabricated NF composite membranes by the interfacial polymerization technique and studied the membrane s surface by AFM. The membrane support was prepared from a dope containing polysulfone (PSf) (P1835-BP Amoco) and poly(vinylpyrrolidone) (PVP) (Fluka) with JV-methyl-2-pyrrolidone (NMP) as the solvent. The top active layer was obtained through interfacial polymerization between trimesoyl chloride (TMC) in hexane and the aqueous phase containing bisphenol A (BPA). Table 5.9 shows the summary of the membrane preparation conditions. The first three membranes identified as PT-30, PT-45, and PT-60 differ in the period of interfacial reaction. The other three membranes identified as PC-05, PC-1, and PC-2 differ in terms of the concentration of BPA in the aqueous phase. The pore sizes determined by AFM and also calculated using the Donnan-steric-... 

Figure 5.40 Synthesis and self-assembly of poly(2,3-dihydro)q butylene-a/t-butylene di-thioether) poly(DHB-a/t-BDT)s. (I) Synthetic pathway and functionalization. (II) Proposed self-assembly route and cross-section view of the membrane (supported by DPD calculations).

Fie, T. (2008) Towards stabilization of supported hquid membranes preparation and characterization of poly sulfone support and sulfonated poly (ether ether ketone) coated composite hollow fiber membranes. 

To enhance the permeation efficiency and selectivity of the polymeric membrane separation, a novel polymeric plasticizer membrane which is composed of cellulose triacetate (CTA) as a membrane support, o-nitrophenyl octyl ether (NPOE) as a membrane plasticizer, and trioctylmethylammonium chloride (TOMAC) as an anion-exchange carrier has been developed. Compared with the poly (vinyl chloride) plasticizer membrane which is widely used for ion-selective electrode, the CTA membrane can contain a larger amount of plasticizer due to a high affinity between CTA and NPOE (25). Thus the plasticizer (NPOE) solubilized in the membrane acts effectively as an organic medium for the carrier mediated membrane separation (25-29). 

Several different membrane supports have been used to make SLMs. These include polypropylene (PP) (31-33), poly(vinylidene difluoride) (PVDF) (34), polytetrafluoroethylene (PTFE) (35), cellulose acetate (36), poly(vinyl chloride) (PVC) (37), and silicones (38,39). The requirement for a good polymeric support are high porosity, small pore size, good mechanical strength for thinness, chemical resistance, hydrophobicity, and low cost. 

Nanofiltration is closely related to RO in that both technologies are used to separate ions from solution. Both NF and RO primarily use thin-film composite, polyamide membranes with a thin polyamide skin atop a poly-sulfone support (see Chapter 4.2.2.2). 

For monolithic disk synthesis, solutions of NBE, DMN-H6, and tris(norborn-5-ene-2-ylmethylenoxy)methylsilane, respectively, in 2-propanol and toluene (25 25 41 9, all wt.%) were subject to ROMP using the first-generation Gmbbs initiator RUCI2 (PCy3)2(CHPh) and triphenylphosphine (PPhs) as modulator. To come up with disks with sufficient mechanical strength, poly (amide) membranes were soaked with the polymerization mixture (Scheme 33). This way, membrane-supported monolithic disks up to 2 mm in thickness were realized. These disks were successfully used for the preconcentration of iodine and selected organic solutes from dilute aqueous samples by SPE. Quantitative measurement of the extracted solutes was achieved by diffuse-reflectance spectroscopy (DRS) directly on the surface of the disk. 

When pressing, the paste can be molded by applying isostatic pressure to obtain a flat product or uniaxial if tubular membranes are required. Sometimes a thermal treatment is simultaneously applied followed by a final sintering. A scanning electron microscopy (SEM) image of a cordierite membrane support is shown in Fig. 6. This support was manufactured from fine cordierite particles (< 120 um in size), mixed with poly(vinyl alcohol) (PVA) (25 wt%) as binder [33]. Water was used as solvent and eliminated by drying and so the resulting paste was uniaxially pressed and heated to 300°C at 2°C/min and then kept at 300°C for 2 h to eliminate PVA. Finally, it was... 

Flat-sheet poly(tetrafluoroethylene) (ETFE), membranes supported by polypropylene (PP) or polyethylene (PE). 

Application of LbL in different fields of nanotechnology has led to the use of various types of porous and rough surfaces for multilayer growth. One significant use has been foimd in the field of separation science, that is, development of filtration membranes by modifying the surface of the porous membrane support to improve separation performance and antifouling properties. Some examples of such porous membrane support materials are polyethersulfone (PES) ultrafiltration membranes, polyacrylonitrile (PAN) ultrafiltration membranes, membrane of PAN with acrylic acid s ments (poly(acrylonitrile-co-acrylic acdd), porous polyacrylonitrile/ polyethylene terephthalate (PAN/PET) substrates, cellulose acetate membranes, porous ceramic supports, and porous alumina supports. The multilayer materials used for such modifications are listed, but not limited to, common polyelearolytes used for LbL applications, such as PSS, PAH, PDADMAC, PAA, and poly(vinyl sulfate) (PVS) copolymers such as poly(4-styrenesulfonic acid-co-maleic acid) quaternary ammonium salts such as cetyl trimethyl ammonium chloride and tetramethyl ammonium chloride as cationic species or nanoparticles such as Ti02. 

Polymeric membranes utilized for nano- and ultrafiltration applications are usually produced by the phase inversion process. Unlike in reverse osmosis, there is no continuous thin dense skin on the membrane surface. The membrane, however, has a tighter pore surface than the bulk of the membrane to allow the desired separation. The bulk of the membrane is much more open, to provide membrane support while limiting the resistance to water flux. Polymers employed in these membranes include polysulfone, poly(ether sulfone), polyacrylonitrile, poly(vinylidene fluoride), aromatic polyamides, sulfonated poly(ether sulfone), and cellulose acetate. 

Other strategies for producing hydrophobic membranes for MD are the modification of hydrophilic polymers or ceramic materials. Qtaishat et al. [144] produced two different types of hydrophobic surface-modifying macromolecules (SMMs) and prepared hydrophobic/hydrophilic polyetherimide composite membranes. The SMMs blended PEI membranes achieved better DCMD fluxes than those of a commercial PTFE membrane tested under the same conditions. Similarly fluorinated SMMs were used to modify hydrophilic poly(sulfone) [145]. Krajewski et al. [146] used lH,lH,2H,2H-perfluorodecyltriethoxysilane to create a hydrophobic active layer on commercial tubular zirconia membranes supported on alumina. The produced membranes were tested in air-gap MD (AGMD). Hendren et al. [147] used 1H,1H,2H,2H-perfluorodecyltriethoxysilane, trichloromethylsilane, and trimethylchlorosilane to modify, by surface grafting, two types of alumina Anodise ceramic membranes. The authors demonstrated that this surface treatment was effective and tested the produced membranes in DCMD. 

Another type of membrane is the dynamic membrane, formed by dynamically coating a selective membrane layer on a finely porous support. Advantages for these membranes are high water flux, generation and regeneration in situ abiUty to withstand elevated temperatures and corrosive feeds, and relatively low capital and operating costs. Several membrane materials are available, but most of the work has been done with composites of hydrous zirconium oxide and poly(acryhc acid) on porous stainless steel or ceramic tubes. 

Ionic liquids have already been demonstrated to be effective membrane materials for gas separation when supported within a porous polymer support. However, supported ionic liquid membranes offer another versatile approach by which to perform two-phase catalysis. This technology combines some of the advantages of the ionic liquid as a catalyst solvent with the ruggedness of the ionic liquid-polymer gels. Transition metal complexes based on palladium or rhodium have been incorporated into gas-permeable polymer gels composed of [BMIM][PFg] and poly(vinyli-dene fluoride)-hexafluoropropylene copolymer and have been used to investigate the hydrogenation of propene [21]. 

Chapman et al. [131] reported the synthesis of poly(ethylene oxide) (PEO) supported dendritic f-BOC-poly(a, c-L-lysines). These dendritic polymers termed as hydramphiphiles formed foams possessing good temporal stability in aqueous solution. Scrimin et al. [132] synthesized a three-directional polypeptide having uses in membrane permeability modulation. Decapeptide fragments were linked to TREN [tris(2-aminoethyl)amine] core. 

Van Koten and Frey used a hyperbranched poly(triallylsilane) as the support for palladium- pincer complexes.[63] The supported palladium-pincer complexes were applied in the catalytic aldol condensation of benzaldehyde and methyl isocyanate. Their activity was similar to that of single site Pd catalysts. According to the authors, the complex is suitable for continuous membrane applications, as demonstrated by their purification by means of dialysis. 

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