Hollow fiber membranes studies

In the present study, we fabricated hollow fiber membrane modules and performed experiments at several conditions. The energy consumption of this process is compared to those of conventional gas absorption processes and membrane gas separation processes. 

Nonbiological methods for removal of trichloroethylene from water are also being studied. These include the use of a hollow fiber membrane contactor (Dr. A.K. Zander, Clarkson University), photocatalysis by solar or artificially irradiated semiconductor powders (Dr. G. Cooper, Photo-catalytics, Inc.), and micellar-enhanced ultrafiltration (Dr. B.L. Roberts, Surfactant Associates, Inc.). 

Recently, an approach mimicking the GI tract and feasible for pharmaceutical dissolution studies has been published [47], Coming from the area of nutritional research, this approach reflects some promising aspects, such as relevant luminal pH values, peristalsis, luminal bacterial colonization, and relevant fluid volumes. However, permeation is only reflected by diffusion through hollow fiber membranes and thus is not in the scope of this chapter. Nevertheless, it will be interesting to see whether it will be possible to expand such a perfect in vitro device toward a more realistic intestinal epithelium. 

Demetriou et al. [25] described a capillary hollow fiber membrane based bioreactor in which microcarrier-attached hepatocytes are placed in the extracapillary space on the exterior surface of the capillary hollow fiber membranes as shown in Fig. 1. Recent experimental studies with this device have demonstrated its efficacy in animal models. By using cryopreserved microcarrier-attached hepatocytes this system offers the convenience of being readily available when needed. 

In order to develop the liquid membrane techniques, i.e., emulsion Hquid membrane (ELM), supported liquid membrane (SLM), non-dispersive extraction in hollow fiber membrane (HFM), etc., for practical processes, it is necessary to generate data on equilibrium and kinetics of reactive extraction. Furthermore, a prior demonstration of the phenomena of facilitated transport in a simple liquid membrane system, the so-called bulk liquid membrane (BLM), is thought to be effective. Since discovery by Li [28], the liquid membrane technique has been extensively studied for the separation of metal ion, amino acid, and carboxyHc acid, etc., from dilute aqueous solutions [29]. 

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). 

In the present work, continuous extraction of lactic acid from an aqueous solution with a solvent consisting of Alamine 336 and 2-octanol in a hollow-fiber membrane extractor was studied. The lactic acid in the solvent... 

The liquid velocity in the hollow-fiber membrane extractor affects the thickness of the liquid film on the membrane surface and, thus, may affect the mass transfer rates in the extractor and back extractor. In the present study, one flow rate was varied from 20 to 120 mL/min, whereas the other two flow rates were kept at 80 mL/min. As shown in Fig. 7,... 

The use of membrane introduction mass spectrometry (MIMS) was first reported in 1963 by Hoch and Kok for measuring oxygen and carbon dioxide in the kinetic studies of photosynthesis [46], The membrane module used in this work was a flat membrane fitted on the tip of a probe and was operated in the MIS mode. The permeated anaytes were drawn by the vacuum in the MS through a long transfer line. Similar devices were later used for the analysis of organic compounds in blood [47], Memory effects and poor reproducibility plagued these earlier systems. In 1974, the use of hollow-fiber membranes in MIMS was reported, which was also operated in the MIS mode [48], Lower detection limits were achieved thanks to the larger surface area provided by hollow fibers. However, memory effects caused by analyte condensation on the wall of the vacuum transfer line remained a problem. 

Sharpe, I. D., Ismail, A. F., and Shilton, S. J. (1999), A study of extrusion shear and forced convection residence time in the spinning of polysulfone hollow fiber membranes for gas separation, Sep. Purif. Technol, 17,101-109. 

There have been numerous studies exploring the concept of membrane reactors. Many of them, however, are related to biotechnological applications where enzymes are used as catalysts in such reactions as saccharification of celluloses and hydrolysis of proteins at relatively low temperatures. Some applications such as production of monoclonal antibodies in a hollow fiber membrane bioreactor have just begun to be commercialized. 

Jian-Mei, L., et al. Microporous polypropylene and polyethylene hollow fiber membranes. Part 3. Experimental studies on membrane distillation for desalination. Desalination, 115, 153, 2003. 

Chen and Lee [24] studied lactic acid production from dilute acid pretreated a-cellulose and switchgrass by L. delbruckii NRRL-B445 in the presence of a fungal cellulase in a fermentor extractor employing a microporous hollow fiber membrane (MHF). This reactor system was operated in a fed-batch mode with continuous removal of lactic acid by in situ extraction. A tertiary amine (alamine... 

X-Ray Diffraction Studies on Reverse Osmosis Hollow Fiber Membranes... 

Experimental. The hollow fiber membranes used for this study were Naflon 811, which Is a copolymer of polysulfonyl fluoride vinyl ether and polytetrafiuoroethylene, and sulfonated and/or quaternated derivatives of polyethylene (kindly supplied by Dr. E. Korngold from Ben Gurlon University In Israel). The aqueous alcohol solutions studied thus far are those of methanol, ethanol and 2-propanol. The separations were accomplished via the pervaporatlon process as described In Reference 9. Counter Ions were replaced In the hollow fiber by soaking the permeator for twenty four hours In 1 molar solutions of the pertinent Ions. For example, experiments were conducted with Na as a counter Ion. When this set of experiments was finished, the sodium was exchanged by Ll etc. Each data point shown In Figure 14 consists of 6 to 10 measurements taken over a time period of 8 hours. Re-runs with the various counter Ions proved that the intrinsic properties of the membrane remain unchanged and the permeability measurements are reproducible. 

In one of the early studies Cho and Hwang [3.54] studied the integration of continuous fermentation and membrane separation using ethanol selective silicone rubber hollow-fiber membranes. Relative to conventional continuous fermentation, the performance of PVMBR resulted in high yeast cell densities, reduction of ethanol inhibition, longer substrate residence time of, more glucose consumption, and recovery of clean and concentrated ethanol. A 10-20 % increase in ethanol productivity was achieved. Kaseno et al. 

Steady state models of membrane bioreactors utilizing a multi-enzyme system, which in addition to the main reaction promotes the simultaneous regeneration of the co-factor (for further discussion see Chapter 4) have been developed by different groups in Japan [5.109, 5.110]. Several of these studies have also considered the effect of backmixing [5.111, 5.112]. A model of an enzymatic hollow fiber membrane bioreactor with a single enzyme, which utilizes two different substrates (reaction 5.42) has been developed recently by Salzman et al [5.113]. 

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