Poly hollow fiber

For the separation of D,L-leucine, Ding et al. [62] used poly(vinyl alcohol) gel-coated microporous polypropylene hollow fibers (Fig. 5-11). An octanol phase containing the chiral selector (A-n-dodecyl-L-hydroxyproline) is flowing countercur-rently with an aqueous phase. The gel in the pores of the membrane permits diffusion of the leucine molecules, but prevents convection of the aqueous and octanol phase. At a proper selection of the flow ratios it is possible to achieve almost complete resolution of the D,L-leucine (Fig. 5-12). 

Controlled release fiber systems based on aliphatic polyesters were investigated by Dunn and Lewis (51-54). The feasibility of hollow fibers spun from poly (L-lactide) and containing the contraceptive steroid levonorgestrel has been demonstrated (55). 

Polymethines, typical soluble dye applications, 7 376t Polymethylene, 20 149 Polymethylene wax, 26 220 Poly(methyl methacrylate) hollow fiber membranes, 16 21 Poly(methyl methacrylate) sheet, properties of, 16 292t Poly(methyl methacrylate) (PMMA),... 

There has been considerable research on chlorine-resistant RO membranes (48—52). A poly(/>mf-2,5 dimethyl)piperazinthiofurazanamide used in the presence of low (3 mg/L) concentrations of chlorine resulted in a membrane life of three years (48). A copolyamide hollow-fiber membrane for use in desalination has been developed that is resistant to 0.5 mg/L chlorine (49). Millipore Corporation has also developed a sulfonated polysulfone member that has desirable chlorine-resistance properties. 

One of the philosophical bases of this work is the relative surface area benefit of microcapsules vs. hollow fibers. It is also felt that the alginate hydrogel would have a higher flux rate than the poly sulfone used in hollow fibers. The study of this technique, however, has only been advanced through a rat model. The survival rate for induced liver failure was 46.7% vs. 0% for untreated animals. 

Poly(vinylidene fluoride), tangential flow. Regenerated cellulose hollow fiber. 

Polymer precipitahon by cooling to produce microporous membranes was hrst developed and commercialized by Akzo [33,37], which continues to market microhltration polypropylene and poly(vinylidene fluoride) membranes produced by this technique under the trade name Accurel . Flat sheet and hollow fiber membranes are made. Polypropylene membranes are prepared from a solution of polypropylene in N, A-bis(2-liydroxyethyl)tal lowamine. The amine... 

He, T. (2008) Towards stabilization of supported liquid membranes preparation and characterization of polysulfone support and sulfonated poly (ether ether ketone) coated composite hollow-fiber membranes. Desalination, 225, 82. 

Polymeric materials are still the most widely used membranes for gas separation, and for specific apphcations the separation technology is well established (see Section 4.6). Producing the membranes either as composites with a selective skin layer on flat sheets or as asymmetric hollow fibers are well-known techniques. Figure 4.5 shows an SEM picture of a typical composite polymeric membrane with a selective, thin skin layer of poly(dimethyl)siloxane (PDMS) on a support structure of polypropylene (PP). The polymeric membrane development today is clearly into more carefully tailored membranes for specific... 

In dialysis, size exclusion is the main separation mechanism, while osmotic pressure and concentration difference drive the transport across two typically aqueous phases. While dialysis is used in some analytical separations, dialysis for the removal of toxins from blood (hemodialysis) is the most prominent application for hollow fiber technology in the biomedical field. The hemodialyzers are used to treat over one million people a year and have become a mass produced, disposable medical commodity. While the first hemodialyzers were developed from cellulosic material (Cuprophane, RC, etc.), synthetic polymers such as polyacrylonitrile, poly(ether) sulfone, and polyvinyl pyrrolidone are increasingly used to improve blood compatibility and flux. Hemodialyzer modules consist of thousands of extremely fine hollow fibers... 

Liu, Y. Chung, T.S. Wang, R. Liu, D.F. Chng, M.L. Chemical cross-linking modification of polyimide/poly(ethersulfone) dual layer hollow fiber membranes for gas separation. Industrial Engineering Chemistry Research 2003, 42 (6), 1190-1195. 

This is analogous to the extraction of sugars with boronic acids described earlier. The recovery of phenylalanine from a fermentation broth has been simplified by using a microporous poly(tetrafluoroethylene) membrane with tri-/j-octylmethylammonium chloride in toluene in the pores.133 Phenylalanine can also be separated using the quaternary ammonium salt with 2-nitrophenyl octyl ether in a cellulose triacetate membrane.134 Kerosene flowing in hollow fiber membranes can remove 99.9% of organic pollutants, such as benzene, p dichlorobenzenc, chloroform, and carbon tetrachloride, from wastewater outside the fibers.135... 

Ethylene has been separated from ethane by a silver nitrate solution passing countercurrent in a hollow fiber poly-sulfone.165 This separation has also been performed with the silver nitrate solution between two sheets of a polysilox-ane.166 A hydrated silver ion-exchanged Nafion film separated 1,5-hexadiene from 1-hexene with separation factors of 50-80.167 Polyethylene, graft-polymerized with acrylic acid, then converted to its silver salt, favored isobutylene over isobutane by a factor of 10. Olefins, such as ethylene, can be separated from paraffins by electroinduced facilitated transport using a Nafion membrane containing copper ions and platinum.168 A carbon molecular sieve made by pyrolysis of a polyimide, followed by enlargement of the pores with water at 400 C selected propylene over propane with an a-valve greater than 100 at 35°C.169... 

Alginate-polylysine has been used to encapsulate hepatocytes (32-34), parathyroid cells (35) and growth hormone transfected fibroblasts (36). Poly (acryl-onitrile/vinyl chloride) (PAN/PVC) macrocapsules have been used with PC12 (37, 38), embryonic mesencephalon tissue (39), thymic epithelial cells (40), adrenal chromaffin cells (41) and islets (25) using preformed hollow fibers or more recently coextrusion techniques (41) similar to those we have developed microcapsules cannot be made since DMSO is used as the solvent. All these studies have concluded from the maintenance of viability of the islets or cells that immunoprotection provided by the capsule membrane was compatible with... 

I. Cabas so, E. Klein, and J. K. Smith, Research and Development of NS-1 and Related Poly-stdfone Hollow Fibers for Reverse Osmosis Desalination of Seawater, report prepared for Office or Water Research and Technology, Gulf South Research Institute, July 1975. 

Asymmetric membranes are made from solution in the form of a hollow fiber, but the process used to form a thin, pore free dense layer on these hollow fibers is not disclosed.45 46 However, US patent 4,440,64312 describes a unique process for producing pore-free polyimide composite membranes. An asymmetric polyimide porous substrate is prepared from solution. When fully imi-dized, the substrate is insoluble. The substrate can now be coated with a poly-amic acid from dilute solution (— 1 %). When fully imidized, the resultant polyimide coating becomes the separating layer. This process allows use of the same or different polyimides for the substrate and the separating membrane. While the examples in the reference describe preparation of flat sheet membranes, this process could be used to prepare hollow fiber membranes. 

Hollow fibers and spheres of zeolite (labeled as HFZ and HSZ, respectively) were successfully fabricated using carbon fibers and polystyrene (PS) spheres as templates respectively, through layer-by-layer technique, coupled with removal of the templates by calcination. The optimum performance conditions to obtain these kinds of materials were systematically studied. The wall thickness and composition of these novel materials can be readily tailored by varying the number of nanozeolite/PDDA (poly(diallyldimethyl ammonium chloride)) deposition cycles and zeolite type used, respectively. The properties of these novel materials were characterized by means of XRD, IR and SEM. 

SH3 Shang, M., Matsuyama, H., Teramoto, M., Lloyd, D.R., and Kubota, N., Preparation and membrane performance of poly(ethylene-co-vinyl alcohol) hollow fiber membrane via thermally induced phase separation, Polymer, 44, 7441, 2003. 

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