Poly porous membranes development

Two useful membranes developed by the group at the Oak Ridge National Laboratory have dominated the application of dynamic membranes the hydrous zirconium oxide ultrafilter and the hydrous zirconium oxide-poly(acrylic acid) hyperfilter. The technology of formation and utilization of zirconium oxide-poly(acrylic acid) dynamic membranes has been described in detail by Thomas ( ). The effects of molecular weight of the poly(acrylic acid), pore diameter of the porous support, formation cross-flow velocity, formation pressure, and pH of poly(acrylic acid) solution during initial deposition of the polyacid on the hyperfiltration performance are described and discussed. 

An example of enzyme immobilized by adsorption was described by Gao and others, who developed a PDMS microreactor for proteolytic digestion with online ESI-MS identification [89]. Trypsin was adsorbed in a poly(vinylidine fluoride) porous membrane. Peptide identification for Cyt< was reported using as little as 0.04 pmol. 

Rajadzadeh et al. have developed porous membranes from poly(vinylidene fluoride)/ poly(methyl methacrylate) (PMMA) in different proportions. Water permeability increases were observed when a higher amount of PMMA was added up to a maximum of 30%. Membranes have been found to have applications regarding electronic devices or organic fillers [40],... 

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. 

Up to now, a variety of non-zeolite/polymer mixed-matrix membranes have been developed comprising either nonporous or porous non-zeolitic materials as the dispersed phase in the continuous polymer phase. For example, non-porous and porous silica nanoparticles, alumina, activated carbon, poly(ethylene glycol) impregnated activated carbon, carbon molecular sieves, Ti02 nanoparticles, layered materials, metal-organic frameworks and mesoporous molecular sieves have been studied as the dispersed non-zeolitic materials in the mixed-matrix membranes in the literature [23-35]. This chapter does not focus on these non-zeoUte/polymer mixed-matrix membranes. Instead we describe recent progress in molecular sieve/ polymer mixed-matrix membranes, as much of the research conducted to date on mixed-matrix membranes has focused on the combination of a dispersed zeolite phase with an easily processed continuous polymer matrix. The molecular sieve/ polymer mixed-matrix membranes covered in this chapter include zeolite/polymer and non-zeolitic molecular sieve/polymer mixed-matrix membranes, such as alu-minophosphate molecular sieve (AlPO)/polymer and silicoaluminophosphate molecular sieve (SAPO)/polymer mixed-matrix membranes. 

The poly(ether/amide) thin film composite membrane (PA-100) was developed by Riley et al., and is similar to the NS-101 membranes in structure and fabrication method 101 102). The membrane was prepared by depositing a thin layer of an aqueous solution of the adduct of polyepichlorohydrin with ethylenediamine, in place of an aqueous polyethyleneimine solution on the finely porous surface of a polysulfone support membrane and subsequently contacting the poly(ether/amide) layer with a water immiscible solution of isophthaloyl chloride. Water fluxes of 1400 16001/m2 xday and salt rejection greater than 98% have been attained with a 0.5% sodium chloride feed at an applied pressure of 28 kg/cm2. Limitations of this membrane include its poor chemical stability, temperature limitations, and associated flux decline due to compaction. 

These include membranes made of liquid electroactive substances or with electroactive substances dissolved in a suitable non-volatile, water-immiscible solvent (mediator). In early designs, the organic phase was placed between two aqueous phases in bulk or with the support of a thin, porous cellulose sheet, sintered glass, or the like. As work with these sensors proceeded, more durable polymer supports were developed, most often poly(vinyl chloride) (PVC). An electroactive... 

Reports are also available on CO2 selective membrane reactors for WGS reaction. Zou et al. [40] first time synthesized polymeric C02-selective membrane by incorporating fixed and mobile carriers in cross-linked poly vinyl alcohol. Micro-porous Teflon was used as support. They used Cu0/Zn0/Al203 catalyst for low temperature WGS reaction. They investigated the effect of water content on the CO2 selectivity and CO2/H2 selectivity. As the water concentration in the sweep gas increased, both CO2 permeability and CO2/H2 selectivity increased significantly. Figure 6.18 shows the influence of temperature on CO2 permeability and CO2/H2 selectivity. Both CO2 permeability and CO2/ H2 selectivity decrease with increasing reactimi temperature. After the catalyst activation, the synthesis gas feed containing 1% CO, 17% CO2, 45% H2 and 37% N2 was pumped into the membrane reactor. They are able to achieve almost 100% CO conversion. They also developed a one-dimensional non-isothermal model to simulate the simultaneous reaction and transport process and verified the model experimentally under an isothermal condition. 

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