Polypropylene hollow fibers

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). 

These gas transfer membranes or membrane contactors employ microporous polypropylene hollow fiber membranes arranged in a modular design. Oxygenated water flows on the shell side of the hollow fibers, and a strip gas (such as nitrogen) or a vacuum is applied to the inside (lumenside), with the hollow fibers acting as a support medium for intimate contact between the water and gas phases. 

Moeder M, Martin C, Koeller G (2004) Degradation of hydroxylated compounds using laccase and horseradish peroxidase immobilized on microporous polypropylene hollow fiber membranes. J Memb Sci 245(1) 183-190... 

J.J. Kim, T.S. lang, Y.D. Kwon, U.Y. Kim and S.S. Kim, Structural Study of Micro-porous Polypropylene Hollow Fiber Membranes Made by the Melt-Spinning and Cold-Stretching Method, J. Membr. Sci. 93, 209 (1994). 

Ammonia absorption/ desorption from ammonia water 240 Pilot-plant study in a polypropylene hollow-fiber column ammonia is absorbed in diluted sulfuric acid... 

VOC removal from wastewater 246 Air stripping process via a polypropylene hollow-fiber module... 

The design of the first commercial modules has allowed the commercial application of membrane contactors for some specific operations. This is the case of the Membrana-Charlotte Company (USA) that developed the LiquiCel modules, equipped with polypropylene hollow fibers, for the water deoxygenation for the semiconductor industry. LiquiCel modules have been also applied to the bubble-free carbonation of Pepsi, in the bottling plant of West Virginia [18], and to the concentrations of fruit and vegetable juices in an osmotic distillation pilot plant at Melbourne [19]. Other commercial applications of LiquiCel are the dissolved-gases removal from water, the decarbonation and nitrogenation in breweries, and the ammonia removal from wastewater [20]. 

In another type of membrane extraction devices, porous polypropylene hollow fibers are used, often in a disposable way, which minimizes carryover problems and reduces costs [26-33]. On the other hand, manual manipulations are needed, limiting the possibility for automation. With these devices, the extraction can be carried out in a static mode, either in large sample volumes, where the extraction is not intended to be complete, or in small volumes aiming for complete extraction. Usually, stirring is applied to increase the speed of mass transfer. Some typical practical arrangements are shown in Figure 12.2. This type of SLM extraction is often called hollow fiber liquid phase microextraction, or three-phase liquid phase microextraction or two-phase liquid phase microextraction but the terminology in this active field of research has not been settled. Also hollow fibers can be connected in flow systems [34,35]. 

In SLM extraction, the most widely applied type of three-phase membrane extraction, the membrane consists of an organic solvent, which is held by capillary forces in the pores of a hydrophobic porous membrane supporting the membrane liquid. Such membrane support can be either flat porous PTFE or polypropylene membrane sheet or porous polypropylene hollow fibers. Typical solvents are long-chain hydrocarbons like n-undecane or kerosene and more polar compounds like dihexyl ether, dioctyl phosphate, and others. Various additives can increase the efficiency of extraction considerably. The stability of the membrane depends on the solubility and volatility of the organic liquids, and it is generally possible to obtain membrane preparations that are stable up to several weeks. 

A new development reported by Li and Sirkar [141] for MD-based desalination makes use of polypropylene hollow fibers coated with a plasma polymerized sUicone-fluoropolymer. This ultrathin coating on the outside of the fiber was water vapor permeable and was instrumental in decreasing the susceptibility of the composite membrane to wetting and fouling. They reported stable water vapor fluxes between 41 and 79 kg h for runs lasting up to 400 h. 

COBE 14401 W. 65th Way Arvada Apex Polypropylene Hollow fiber ... 

VOCs can also be removed by applying vacuum and using composite membranes as, for example, in the VaporSep process commercialized by the MTR, where a porous support is used for a silicone membrane coating in a spiral wound configuration. Hydrophobic polypropylene hollow fibers with an ultrathin and highly VQC-permeable plasma-polymerized nonporous silicone skin on the outer surface can be also effective [31-33]. 

Figure 2d shows a composite hydrophobic-dense phase membrane. An example of such a membrane is a Celgard X-20 polypropylene hollow fiber porous... 

Johnson, J. N., Cross-flow Microfiltration Using Polypropylene Hollow Fibers, Fifth Annual Membrane Technology Planning Conference, Cambridge (Oct. 1987)... 

Reactor operation. The polypropylene hollow fibers in the reactor were prewetted prior to inoculation with recirculation of 50% ethanol and sterilized chemically with 5% formalin solution. Then the reactor was washed by ultrafiltration of one liter of autoclaved distilled water. The reactor was placed in a water bath maintained at a desired temperature. Cells were inoculated through the inoculation port using a syringe needle. The detailed experimental setup is shown in Figure 3. 

Figure 9. Electron micrograph of densely packed Nocardia medi-terranei (ATCC 21789) cells near the polypropylene hollow fiber (magnification, 25,000X).

A different application involves using the membrane for the delivery of one of the reactants (e.g., bubble-free aeration [4.14]). One recent example of such an application is that reported by Onken and Berger [4.15]. They used a microporous polypropylene hollow-fiber membrane for the controlled addition of oxygen in the biotransformation of cit-ronellol into 3,7-dimethyl-1,6,7-octanetriol by Cystoderma carcharias. 

To design the deaerator, we must first decide on the geometry for the hollow-fiber module. We will use commercially available microporous polypropylene hollow fibers in a module similar to that shown in Figure 2.4. Water at 298 K will flow through the shell side, parallel to the fibers, at a superficial velocity of 10 cm/s. Pure nitrogen at 298 K and 1 atm at the rate of 40 L/min will be used as a sweep gas in countercurrent flow through the lumen. The outside diameter of the available fibers is 290 pm, the packing factor is 40%, and the surface area per unit volume is a - 46.84 cm-1 (Prasad and Sirkar, 1988). 

An alternative approach to solving stability problems with ILMs is presented by Bhave and Sirkar (114). Aqueous solutions are immobilized in the pore structure of hydophoblc, polypropylene hollow fibers by a solvent exchange procedure. Gas permeation studies are reported at pressures up to 733 kPa with the high pressure feed both on the shell and lumen sides of the laboratory scale hollow fiber permeator. No deformation of the hollow fibers is observed. Immobilizing a 30 weight % KjCO, solution in the hollow fibers greatly improved the separation factor, a(C02/Na). from 35.78 with pure water to 150.9 by a facilitated transport mechanism. Performance comparisons with commercial COj separation membranes are made. 

Hollow fibers rather than flat membranes are often the preferred support form for practical gas separation due to the high membrane surface area that can be packed In a permeator and their high pressure capability. In the earlier study (13) the hydrophobic mlcroporous polypropylene hollow fiber support used was Celgard X-20. Due to its dimensions and porosity It could not be operated at positive shell side AP value beyond 282 cm Hg as significant compressive deformation as observed. We have utilized In this study Celgard X-10 hollow fibers. These fibers having a lower porosity and much smaller dimensions can withstand much greater applied pressures whether applied on the outside or on the Inside of the fiber. The performance of such a simple IIJI structure Is the subject at hand. 

Korikov, A. R, Kosaraju, P. B., and Sirkar, K. K. 2006. Interfacially polymerized hydrophilic microporous thin film composite membranes on porous polypropylene hollow fibers and flat films. Journal of Membrane Science 279 588-600. 

Abrol K, Qazi GN, Ghosh AK. Characterization of an anion-exchange porous polypropylene hollow fiber membrane for immobilization of ABL lipase. J. Biotechnol. 2007 128 838-848. 

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