Filtration cellulose

Cellulose acetate and triacetate fibers have survived in the marketplace because they have certain unusual properties that demonstrate significant advantages over other polymerie materials. Cellulose acetate and triacetate textile fibers are luxurious. Fabrics made from them have an excellent hand, dye to brilliant, attractive shades, and are soft and comfortable. Regarding cellulose acetate and triacetate plastics and films, no other polymers can match the sparkling clarity possessed by these. For cigarette-smoke filtration, cellulose acetate offers a unique balance of properties including smoke removal efficiency and contribution to taste that makes it the standard of the industry. 

Hydrophilic membranes and microorganisms can be attached simultaneously to gas diffusion electrodes, such as those sensitive to pNHs [60, 61, 64, 65], p02 [62, 63, 66, 67] and pCOa [68]. The microorganisms are imprisoned in a space defined by a washer [69], or trapped by vacuum suction inK> the pores of a filtration cellulose acetate membrane [68,70]. 

Filtration of viscose is not a straightforward chemical engineering process. The solution of cellulose xanthate contains some easy-to-deal-with undissolved pulp fibers, but also some gel-like material which is retarded rather than removed by the filters. The viscose is unstable and tends to form more gel as it ages. Its flow characteristics make the material close to the walls of any vessel or pipe move more slowly, get older, and gel more than the mainstream viscose. So while filtration can hold back gels arising from incomplete mixing, new gels can form in the pipework after the filters. 

A common surface cartridge is the pleated paper constmction type, which allows larger filtration areas to be packed iato a small space. Oil filters ia the automobile iadustry are of this type. The paper is impregnated, for strength, with epoxy or polyurethane resia. Any other medium ia sheet form, similar to cellulose paper, such as wool, polypropylene, or glass may be used. 

The white cell adsorption filter layer is typically of a nonwoven fiber design. The biomaterials of the fiber media are surface modified to obtain an optimal avidity and selectivity for the different blood cells. Materials used include polyesters, eg, poly(ethylene terephthalate) and poly(butylene terephthalate), cellulose acetate, methacrylate, polyamides, and polyacrylonitrile. Filter materials are not cell specific and do not provide for specific filtration of lymphocytes out of the blood product rather than all leukocytes. 

CMC/PAC sodium carboxy-methyl cellulose anionic 140 filtration control, viscosity builder sensitive to salinity, multivalent ions... 

Dry filters are usually deeper than viscous filters. The dry filter media use finer fibers and have much smaller pores than the viscous media and need not rely on an oil coating to retain collected dust. Because of their greater resistance to air flow, dry filters must use lower filtration velocities to avoid excessive pressure drops. Hence, dry media must have larger surface areas and are usually pleated or arranged in the form of pockets (Fig. 17-64), generally sheets of cellulose pulp, cotton, felt, or spun glass. 

Polymer Membranes These are used in filtration applications for fine-particle separations such as microfiltration and ultrafiltration (clarification involving the removal of l- Im and smaller particles). The membranes are made from a variety of materials, the commonest being cellulose acetates and polyamides. Membrane filtration, discussed in Sec. 22, has been well covered by Porter (in Schweitzer, op. cit., sec. 2.1). 

Filter aids should have low bulk density to minimize settling and aid good distribution on a filter-medium surface that may not be horizontal. They should also be porous and capable of forming a porous cake to minimize flow resistance, and they must be chemically inert to the filtrate. These characteristics are all found in the two most popular commercial filter aids diatomaceous silica (also called diatomite, or diatomaceous earth), which is an almost pure silica prepared from deposits of diatom skeletons and expanded perhte, particles of puffed lava that are principally aluminum alkali siheate. Cellulosic fibers (ground wood pulp) are sometimes used when siliceous materials cannot be used but are much more compressible. The use of other less effective aids (e.g., carbon and gypsum) may be justified in special cases. Sometimes a combination or carbon and diatomaceous silica permits adsorption in addition to filter-aid performance. Various other materials, such as salt, fine sand, starch, and precipitated calcium carbonate, are employed in specific industries where they represent either waste material or inexpensive alternatives to conventional filter aids. 

Acetoin dehydrogenase [from beef liver acetoin NAD oxidoreductase] [9028-49-3] Mr 76000, [EC 1.1.1.5]. Purified via the acetone cake then Ca-phosphate gel filtration (unabsorbed), lyophilised and then fractionated through a DEAE-22 cellulose column. The Km for diacetyl in 40pM and for... 

Purified by Sephadex G-200 filtration and DEAE-cellulose column chromatography. Hexosaminidase A was further purified by DEAE-cellulose column chromatography, followed by an ECTEOLA-cellulose column, Sephadex-200 filtration, electrofocusing and Sephadex G-200 filtration. Hexosaminidase B was purified by a CM-cellulose column, electrofocusing and Sephadex G-200 filtration. [Srivastava et al. 7 Biol Chem 249 2034 1974.]... 

Corticotropin [92307-52-3] polypeptide Mr -4697. Extract separated by ion-exchange on CM-cellulose, desalted, evapd and lyophilised. Then run on gel filtration (Sephadex G-50) [Lande et al. Biochemical Preparations 13 45 1971 Esch et al. Biochem Biophys Res Commun 122 899 1984],... 

Dibydropteridine reductase (from sbeep liver) [9074-11-7] Mr 52,000 [EC 1.6.99.7]. Purified by fractionation with ammonium sulfate, dialysed versus tris buffer, adsorbed and eluted from hydroxylapatite gel. Then run through a DEAE-cellulose column and also subjected to Sephadex G-lOO filtration. [Craine et al. J Biol Chem 247 6082 1972.]... 

Follicle Stimulating Hormone (FSH, foilitropin) [9002-68-0] Mr 36,000. Purified by Sephadex GlOO gel filtration followed by carboxymethyl-cellulose with NH4OAC pH 5.5. The latter separates luteinising hormone from FSH. Solubility in H2O is 0.5%. It has an isoelectric point of 4.5. A soln of Img in saline (lOOmL) can be kept at 60° for 0.5h. Activity is retained in a soln at pH 7-8 for 0.5h at 75°. The activity of a 50% aq EtOH soln is destroyed at 60° in 15 min. [Bloomfield et al. Biochim Biophys Acta 533 371 1978 Hartree Biochem J100 754 1966 Pierce and Parsons Ann Rev Biochem 50 465 1981.]... 

Phosphoribosyl pyrophosphate synthetase (from human erythrocytes, or pigeon or chicken liver) [9015-83-2] Mr 60,000, [EC 2.7.6.1]. Purified 5100-fold by elution from DEAE-cellulose, fractionation with ammonium sulfate, filtration on Sepharose 4B and ultrafiltration. [Fox and Kelley J Biol Chem 246 5739 197h, Flaks Methods Enzymol6 158 1963 Kornberg et al. J Biol Chem 15 389 7955.]... 

This Crude product (15.8 g) In water (360 ml) was added to a prehydrogenated suspension of 10% palladium on charcoal (4 g) in water (400 ml), and hydrogenation was continued for 30 minutes. The catalyst was removed and the filtrate was adjusted to pH 7.5 with sodium bicarbonate, then evaporated at low temperature and pressure. The residue was purified by chromatography on a column of cellulose powder, eluting first with butanol/ ethanol/water mixture and then with acetone/isopropanol/water. The main fraction was evaporated at low temperature and pressure to give a 32% yield of the sodium salt of a-carboxybenzylpenicillin as a white powder. The product was estimated by manometric assay with penicillinase to be 58% pure. 

Dried shrimp was ground, defatted with benzene, and then extracted with cold water. The luciferase extracted was purified first by a batch adsorption onto DEAE cellulose (elution with 0.4 M NaCl), followed by gel filtration on a column of Sephadex G-150, anion-exchange chromatography on a column of DEAE-cellulose (gradient elution 0.05-0.5 M NaCl), and gel filtration on a column of Ultrogel AcA 34. The specific activity of the purified luciferase was 1.7 x 1015 photons s 1 mg-1, and the yield in terms of luciferase activity was about 28%. 

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