Hollow fiber membranes solutions

Fig. 5-12. Separation of d,1-leucine in hollow-fiber membrane extraction using a Al- -dodecyl-l-hydrox-yproline solution in octanol as the enantioselective extraction liquid. The modules used were 32 cm long and contained 96 Celgard X-20 polypropylene fibers [57].

We have been studying the novel process for CO2 separation named membrane/absorption hybrid method. The advantages of this process are that high gas permeance and selectivity were obtained. The concept of this process is shown in Fig. 1. Both feed gas and absorbent solution are supplied to the inside of hollow fibers. While Ae liquid flows upward inside the hollow fibers, absorbent solution absorbs CO2 selectively and it becomes a rich solution. Most of rich solution permeates the membrane to the permeate side maintained at reduced pressure, where it liberated CO2 to become a lean solution. Compared to a conventional gas absorption... 

Enzyme membrane reactor for production of diltiazem intermediate. A solution of the racemic ester in organic solvent enters the port at the bottom of the reactor and flows past the strands of microporous, hollow-fiber membrane that contain an enzyme. The enzyme catalyzes hydrolysis of one enantiomer of the ester that undergoes decarboxylation to 4-methoxyphenylacetaldehyde (which in turn forms a water-soluble bisulfite complex that remains in the aqueous phase). The other enantiomer of the ester remains in the aqueous stream that leaves the reactor via the port at the top. Courtesy of Sepracor, Inc. 

Preparation of Hollow Fiber Membrane. CTA (Cellulose Tri-Acetate) hollow fiber membranes were prepared by aplnning a dope solution of CTA followed by soaking and anealing. 

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]. 

The process design principles of SLM, non-dispersive extraction, and hybrid hquid membrane systems need to be understood through bench scale experiments using feed solution of practical relevance. While the economic analysis of an ELM process can be performed from small scale experiments, such an analysis is difficult for other LM systems. In particular, availability and cost of hollow fiber membranes for commercial application are not known apriori. A simple rule of thumb for cost scale-up may not be apphcable in the case of an HE membrane. Yet we feel that the pilot plant tests would be adequate to make realistic cost benefit analysis of a liquid membrane process, since the volume of production in )8-lactam antibiotic industries is usually low. 

Figure 8.4 shows the data [2] of the UF of serum solutions with a hollow fiber-type ultrafilter, with hollow fibers 16 cm in length and 200 pm in i.d., at four shear rates on the inner surface of the hollow-fiber membrane. Slopes of the straight lines, which converge at a point C = Cq on the abscissa, give values at the shear rates given in the figure. 

Liquid-liquid extraction of hydrophobic oil-laden surfactant solution was evaluated using counter-flow, porous hollow fiber membranes. Our liquid-liquid extraction experiments were conducted using Liqui-Cel Extra-Flow 2.5x8 Membrane Contactor purchased from Celgard LLC (Charlotte, NC). The dimensions of the column are 6.3 cm diameter and 20.3 cm. length with... 

By maximizing the contact area between extraction solvent and surfactant-solubilized hydrophobic oil contaminant through the use of state-of-the-art hollow fiber membrane columns, we hypothesize that hydrophobic oil contaminants can be separated from surfactant solutions without macroemulsification. For this research we were interested in the partitioning of the hydrophobic oil from the hydrophobic environment of the micelle via its aqueous concentration into a more preferred extracting solvent. 

Research on separation processes demonstrated that hydrophobic oilladen surfactant was efficiently regenerated through the use of state-of-the-art hollow fiber membrane columns. Specifically, the hydrophobic oil dodecane was effectively separated from the surfactant system SDBS/IPA/NaCl (Table VI). This separation was accomplished by counterflowing the oil/surfactant solution, comprised of 10.3 ml. dodecane per 100ml. of SDBS/IPA/NaCl solution, with the extraction solvent squalane. These results demonstrate the ability to effectively regenerate and reuse these surfactant systems. 

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... 

Figure 3.33 Twin-orifice spinneret design used in solution-spinning of hollow fiber membranes. Polymer solution is forced through the outer orifice, while bore-forming fluid is forced through the inner capillary...

Another method of producing composite hollow fibers, described by Kusuki etal. at Ube [108] and Kopp et al. at Memtec [109], is to spin double-layered fibers with a double spinneret of the type shown in Figure 3.37. This system allows different spinning solutions to be used for the outer and inner surface of the fibers and gives more precise control of the final structure. Often, two different polymers are incorporated into the same fiber. The result is a hollow fiber composite membrane equivalent to the flat sheet membrane shown in Figure 3.26. A reason for the popularity of composite hollow fiber membranes is that different polymers can be used to form the mechanically strong support and the selective layer. This can reduce the amount of selective polymer required. The tailor-made polymers developed for gas separation applications can cost as much as... 

From 1978 to 1980, Henis and Tripodi [6,23], then at Monsanto, devised an ingenious solution to the membrane defect problem their approach is illustrated in Figure 8.8. The Monsanto group made Loeb-Sourirajan hollow fiber membranes... 

Another type of gas exchange process, developed to the pilot plant stage, is separation of gaseous olefin/paraffin mixtures by absorption of the olefin into silver nitrate solution. This process is related to the separation of olefin/paraffin mixtures by facilitated transport membranes described in Chapter 11. A membrane contactor provides a gas-liquid interface for gas absorption to take place a flow schematic of the process is shown in Figure 13.11 [28,29], The olefin/paraffin gas mixture is circulated on the outside of a hollow fiber membrane contactor, while a 1-5 M silver nitrate solution is circulated countercurrently down the fiber bores. Hydrophilic hollow fiber membranes, which are wetted by the aqueous silver nitrate solution, are used. 

The lipase enzyme stereospecifically hydrolyzes the (+) isomer of naproxen ester. The enzyme is immobilized in the wall of an inside-skinned hollow fiber membrane. The racemic d and / naproxen ester mixture, dissolved in methyl isobutyl ketone, is introduced on the shell side of the fiber and an aqueous buffer solution is circulated through the fiber lumen. The lipase enzyme hydrolyzes the d form of naproxen ester, forming ethanol and naproxen d. Naproxen d is a carboxylic acid soluble in aqueous buffer but insoluble in methyl isobutyl ketone. Consequently naproxen d is removed from the reactor with the buffer solution. The naproxen / ester remains in the methyl isobutyl ketone solution. This technique achieves an essentially complete separation of the d and Z forms. In a clever final step... 

A straightforward way to collect solutes from the interstitial fluid (ISF) space would be to have a semipermeable, hollow fiber, membrane-based device as originally described by Bito et al.1 Two semipermeable membrane-based devices that have been used to collect different types of analytes from various mammalian tissues include microdialysis sampling probes (catheters) and ultrafiltration probes. The heart of each of these devices is the semipermeable polymeric membrane shown in Figure 6.1. The membranes allow for collection of analytes from the ISF that are below the membrane molecular weight cutoff (MWCO). Each of these devices provides a sample that has a significantly reduced amount of protein when compared to either blood or tissue... 

The following processes can be described as selective therapeutic plasmapheresis. In a first step, blood is withdrawn from the patient and separated by crossflow filtration in a hollow-fiber membrane cartridge water and some plasma solutes are transferred through a semipermeable membrane under a convection process. The transmembrane pressure applied from blood to filtrate compartment ensures flow and mass transfers. Then, the filtrate perfuses the adsorption columns where toxins are retained and is finally mixed with blood cells and other plasma components before returning to the patient (Figure 18.11). 

A Hollow-Fiber Membrane Extraction Process for Recovery and Separation of Lactic Acid from Aqueous Solution... 

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... 

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