Hollow Fiber Membrane System Research Articles

Production of Poly-.BETA.-Hydroxybutyrate(PHB) by Fed-Batch Fermentation Using Hollow Fiber Membrane System.

Production of Poly-.BETA.-Hydroxybutyrate(PHB) by Fed-Batch Fermentation Using Hollow Fiber Membrane System.

Controlled Atmosphere Systems for Marine Vessels

Controlled atmosphere (CA) preservation of perishable fruit and vegetables represents new opportunities for today's reefer operators. This technology affords the carrier an efficient and economical method of introducing and maintaining a low oxygen atmosphere that, when used in conjunction with temperature control, can significantly enhance the preservation of fruit and vegetables. Improved product quality, new markets, and reduced product losses are benefits realized through the use of hollow fiber membrane air separation technology. Seasonal products, which may be unavailable because of the transit time of shipping, are now a reality for operators utilizing this technology. High-value products such as fresh cut flowers, previously dedicated to air freight, may be a natural extension of the technology. The authors' company is a wholly owned subsidiary of The Dow Chemical Company. Generon supplies hollow fiber membrane systems for the on-site generation of gaseous nitrogen. In 1992 the company provided turnkey design and installation services of controlled atmosphere systems for three fully refrigerated containerships operated by the Great White Fleet. These ABS-classed vessels were the first of their type to fully utilize controlled atmosphere technology for the improved quality and reduction of perishable losses.

Preparative separation of enantiomers using hollow-fiber membrane technology

Several chromatographically developed chiral selectors show promise for large scale separation of enantiomers using hollow-fiber membrane technology. Chiral selectors derived from N-(1-naphthyl) leucine have been used in a hollow-fiber membrane system (Sepracor) to separate the enantiomers of amino acid derivatives. Enantiomeric purities exceeding 95% have been obtained in a single pass through the system. For data collection, sample sizes were limited to giam quantities of racemate.

A method for chronic membrane plasmapheresis in the rat

Therapeutic apheresis as applied to humans may encompass a single treatment or numerous treatments for disorders ranging from acute poisoning to severe chronic autoimmune disease. However, the mechanisms of beneficial effects of apheresis are not well characterized. Utilizing a miniaturized hollow-fiber membrane system, we have developed a reliable technique for long-term vascular access in the rat that permits repetitive plasmapheresis. We established vascular access in 14 animals, with 8 and 6 rats randomized to 3- and 7-wk experimental periods, respectively. Immunoglobulin levels of blood samples obtained immediately before and after each plasmapheresis were measured to examine membrane filtration characteristics. Overall, 100% of the animals survived and 93% successfully completed their assigned experimental periods. Mean decrease of immunoglobulin G and M levels for 28 plasmapheresis treatments in five rats was 66.9 +/- 8.1 and 61.0 +/- 7.3% (SD), respectively, indicating effective membrane filtration. This model of apheresis can be applied to several disorders in the rat, including, but not limited to, spontaneous insulin-dependent diabetes mellitus and experimental inflammatory bowel disease.

Cation Separations Using A Proton-Ionizable Macrocycle in a Dual Module Hollow Fiber Membrane System

Abstract Separation of metal cations in aqueous solution using a proton-ionizable macrocycle in a dual module hollow fiber membrane system is described. The advantages of this system, such as easy access to all phases, rapid transport rates, and the potential for continuous operation are maintained with the proton-ionizable macrocycles which allow for proton driven transport. Transport is diffusion limited in the organic phase boundary layer near and on the fibers. Hence, the selectivity of the extraction system is maintained. Selective transport of Ag+ over all other cations tested from neutral source phases and of K+ over other alkali metal cations from basic source phases using a triazole-18-crown-6 carrier has been demonstrated. Selective K+ transport from less basic source phases has been demonstrated using the more acidic thiopyridone-18-crown-6 ligand. However, the large aqueous partition of this ligand makes it difficult to maintain it in the organic phase. Design of the separation systems require...

Gas extraction kinetics of volatile organic species from water with a hollow fiber membrane

Two mathematical descriptions of the solvent-free extraction process occuring in a hollow fiber membrane system are described. A model solving the diffusion equation and considering the concentration distribution accros the diameter and along the axis of the fiber has an analytical solution. Mass transfer through the aqueous phase, membrane, and stripping phase has a semiempirical solution

On the standardization of performance data for reverse osmosis desalination plants

Comprehensive operating data, generated over a period of more than 3 years by Doha Reverse Osmosis Plant (DROP) in Kuwait, has been used to compare the accuracy of two different methods for standardizing RO performance data. The ASTM method, applied for both spiral wound and hollow fibre membrane systems, and the UOP method, applied to spiral wound membrane systems, were used in this study. The UOP method resulted in better standardization of both permeate flowrate and salt rejection for both stages of the spiral wound membrane system configuration. For a plant operation time of 36 months, the average differnece between both methods was 1.2% and 5.8% for the salt rejection of first and second stage respectively and 8.0% nd 4.6% for the permeate flowrate of first and secons stage respectively. The UOP method does need, however, more detailed input data compared to the ASTM method. An attempt was made to modify the UOP method for application with the hollow fibre membrane system configuration. A smaller difference range for salt rejection was obtained, ranging between 0.8% for the first stage and 2.0% for the second stage. On the other hand, the average difference between the two methods was 15.3% and 9.4% for the permeate flowrate leaving the first and second stage respectively. The standardized performance data using UOP method were closer to the plant design data.

Hollow-fiber membrane systems as suppressors in ion chromatography

Ion-exchange hollow fibers have been used for exchange of cations in ion-chromatography effluents. The hollow fibers replace the conventional ion-exchange resin columns used to reduce the conductivity of the effluent by converting the sodium carbonate eluent to carbonic acid. The membrane system shows significant advantage over the dual ion-exchange column method in both ease of operation and superior stability of the chromatography system. Elution times and detector response for acetate ion, for example, were far more consistent and linear for the membrane system.

Continuous simultaneous saccharification and fermentation of starch using Zymomonas mobilis

A continuous process involving simultaneous saccharification and fermentation of liquefied starch has been developed using Zymomonas mobilis. Amyloglucosidase retention and cell recycle have been effected by using an Amicon hollow-fiber membrane system with a MW cutoff of 5000. Relatively high productivities of up to 60 g L(-1) h(-1) have been achieved at ethanol concentrations of 60-65 g/L. The system also offers the potential for reduced enzyme requirements for saccharification.