Membranes ultra-filtration

Porter, M.C., "Concentration Polarization with Membrane Ultra-filtration", Ind. Eng. Chem. Prod. Res. Develop.,1972, 11 (3), 234-248... 

Knutsen JS, Davis RH. (2004). Cellulase retention and sugar removal hy membrane ultra-filtration during lignocellulosic biomass hydrolysis. Appl Biochem Biotechnol, 114, 585-599. 

Anotlier standard metliod is to use a (high-speed) centrifuge to sediment tire colloids, replace tire supernatant and redisperse tire particles. Provided tire particles are well stabilized in tire solvent, tliis allows for a rigorous purification. Larger objects, such as particle aggregates, can be fractionated off because tliey settle first. A tliird metliod is (ultra)filtration, whereby larger impurities can be retained, particularly using membrane filters witli accurately defined pore sizes. 

Ultra filtration. This process removes macromolecules, microorganisms, particulate matter, and pyrogens using a thin, selectively permeable membrane. Ultrafiltration caimot remove ions from water and is generally employed as a polishing process. 

As RO membranes become looser their salt rejection falls (see Section 31.8.1). Eventually a point is reached at which there is no rejection of salts, but the membrane still rejects particulates, colloids and very large molecules. The membrane pore size can be tailored to a nominal molecular weight cut-off. The resulting filtering process is called ultra-filtration. 

Kragl and Dreisbach (1996) have carried out the enantioselective addition of diethyl zinc to benzaldehyde in a continuous asymmetric membrane reactor using a homogeneous soluble catalyst, described in their paper. Here a,a-diphenyl-L-proline was used as a chiral ligand, coupled to a copolymer made from 2-hydroxy ethyl methacrylate and octadecyl methacrylate, which had a sufficiently high molecular weight to allow separation by ultra-filtration (U/F). The solvent-stable polyaramide U/F Hoechst Nadir UF PA20 retained more than 99.8% of the catalyst. The ee was 80 %, compared to 98 % for a noncoupled catalyst. 

Ultra- filtration Water sample la filtered under pressure through a membrane that will pass molecular constituents below a certain size and retain those above that size. Large molecules Porosity of membrane daterminaa the size of molecules concentrated. Usually used for compounds > 1000 molecular weight. Can concentrate large sample volumes at low temperatures. 

Membrane filtration processes, such as reverse osmosis, and micro and ultra filtration, are used to filter out dissolved solids in certain applications see Table 10.9. These specialised processes will not be discussed in this book. A comprehensive description of the techniques used and their applications is given in Volume 2, Chapter 8 see also Scott and Hughes (1995), Cheryan (1986), McGregor (1986) and Porter (1997). 

This blend is recommended as thin-gel composite membranes for bovine serum albumin ultra-filtration [114],... 

Since membrane filtration methods such as ultra filtration or nanofiltration can discriminate according to the size of a given molecule, they can easily be used to retain biocatalysts (which are macromolecules). For chemical catalysts additional procedures have to be applied mostly. Immobilization on a solid support is used... 

Jeon, Y. J. and Kim, S. K. (2002). Antitumor activity of chitosan oligosaccharides produced in an ultra filtration membrane reactor system. J. Microbiol. Biotechnol. 12,503-507. 

Acetylcholineesterase Biosensors were fabricated from filter-supported solventless bilayer lipid membrane (BLM) and used for the analysis of the substrates of hydrolytic enzymes in a flowthrough system. The codeposition of lipid (dipalmitoyl-phosphatidic acid) and protein solutions to form a BLM on a microporous glass fiber or polycarbonate ultra-filtration membrane disc was described. Enzyme was immobilized on the membrane by incorporation of protein solution into the lipid matrix at the air-electrolyte interface before BLM formation. 

If it is thought to be an advantage to increase the activity of the conditioned medium, this may be achieved by concentrating it fourfold using a lOkD molecular weight cut-off membrane. This should be done before the final sterile filtration. There are many types and makes of ultra-filtration equipment available on the market. 

In addition to the traditional deep bed filtration, other interesting examples of different processes and techniques can be described by the same basic principle (i) the tangential micro-filtration and ultra-filtration where a slow deep filtration produces the clogging of the membrane surface (ii) some processes of impregnation of porous supports with a sol in order to form a gel which, after precipitation, will form a membrane layer. Here the sol penetration inside the support is fundamental for the membrane quality. 

Ultra-filtration. A membrane with a very small pore size is used to remove solute or colloids from pressurized waste streams. It retains the larger particles and allows the solvent and small particles of interest to pass through. 

High-purity WPC (i.e., 70-95% proteins or total solids) can be produced by thermocalcic aggregation, followed by microfiltration, ultra filtration and diafiltration of whey proteins. Ultraflltration has been practiced since early 1970s. It appears that zirconia membranes on carbon supports with a MWCO of 10,000 to 20,000 daltons and zirconia membranes on alumina supports with a pore diameter of 0.05 to 0.1 pm are suitable for this purpose. A permeate flux of as high as 60 L/hr-m for processing acid whey to a protein content of 25 to 37% using a zirconia membrane with a MWCO of 10,000 daltons has been reported [Merin and Daufin, 1989]. 

Microriltraticiii and ultraTiltratiop of lees or crude wines. More specifically, crossflow micro- and ultra-filtration ceramic membranes have the potential for replacing all the above separation steps except cold treatment [Castelas and Serrano, 1989]. When using inorganic membranes for removing bacterias, yeasts or suspended particles, the choice of the pore size is very important in determining the filtrate flux and the rejection performance of these materials from wines. 

Merin and Daufin [44] and Bhave [3] present a comprehensive review of the field, the main use of ceramic membranes being protein concentration by micro-or ultra-filtration and bacteria removal by microfiltration. For the latter the Bactocatch process, as described by Gillot et al. [47], Merin and Daufin [44] and Bhave [3] forms an important example. At an average flux of 7001/m h 99.7% of the bacteria are withheld without retaining the proteins. 

Another solute-membrane interaction, formation of a precipitated gel at the solution-membrane Interface, is also not considered in our model. Gel formation during protein ultra-filtration is a major premise of many theoretical and experimental studies, but as is discussed later, there was no evidence for gel formation during the experiments with protein containing systems. All of our mathematical modeling and data analysis is for the pregel region of hemofiltration. 

Figure 2 shows a generalized view of reverse osmosis/ultra-filtration. You will note that the artist has purposely shown the membrane having an isotropic nature, i.e., a dense topskin with small pores with a very porous support layer. The feed... 

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