Ultrafiltration introduction

P. Zumbusch, W. Kulcke, G. Brunner. Use of alternating electric fields as antifouling strategy in ultrafiltration of biological suspensions. Introduction of a new experimental procedure for crossflow filtration. J Memb Sci 142-.15 (1998). R. L. Rowley, T. D. Shupe, M. W. Schuck. A direct method for determination of chemical potential with molecular dynamics simulations. 1. Pure components. Mol Phys 52 841, 1994. 

The explanation of the pressure-independent region during the ultrafiltration of macromolecules requires the arbitrary introduction of the concept of a gel-layer in the film model. A more complete description of the dependence of the membrane permeation rate on the applied pressure may be given by considering the effect of the osmotic pressure of the macromolecules as described by Wijmans et alS18 Equation 8.2 may then be written as ... 

Theoretically, polymer-containing wastewater from desizing can be purified for water recycling by removal and reconcentration of the polymer by ultrafiltration or evaporation, but the high costs of investment and additional expenses for the disposal of the concentrate hinder the introduction of such techniques as a general treatment process. 

Although whey protein products have several food uses, the lactose contained in the permeate is less valuable, and many plants discharge the permeate to a biological wastewater treatment plant. A few plants recover lactose as dry lactose sugar, as shown in Figure 6.23. Some plants also ferment the lactose concentrate to make ethanol. An introduction to membrane ultrafiltration in cheese production is given by Kosikowski [26],... 

After the introduction of pronase E, other more or less nonsubstrate-specific proteolytic enzymes have been applied to assist Se speciation. Most of them were derived from DNA/RNA clean-up protocols. The new enzymes (subtilisin from Bacillus licheniformis, also named protease VIII, EC 3.4.21.14 proteinase K from Tritirachium album, EC 3.4.21.64 the crude Novo Nordisk product of Flavourzyme from Aspergillus oryzae) proved to be capable of extracting Se with varying yields and chromatographic recovery of Se species. It is important to highlight that the latter parameter also depends on the instrumentation available. In this regard, different recovery values for the same samples reported by independent research groups do not necessarily indicate successful or unsuccessful sample preparation. Similarly, extraction efficiency (defined as the ratio of extracted Se to total Se in the sample) cannot be used as such for comparison purposes because sample preparation may include some extra steps, for example, TCA precipitation or ultrafiltration, which may reduce this value even by 10-20 percent. 

Ultrafiltration permselectivity of a ceramic membrane can be enhanced by applying an electric field to the surface of the electrically conductive membrane [Guizard et al., 1986a]. The electric field is created using two electrodes with the conductive membrane being the anode or cathode. Such conductive membranes can be prepared with the introduction of a proper amount of Ru02 to Ti(>2. 

There remain some exciting challenges in the oil-refining industry for the future. The introduction of new technologies (e.g., use of enzymes, ultrafiltration, etc.) may require the development of specific refining and deodorization methods. 

Most of the earlier studies on the immobilization of enzymes were directed towards the attachment of the enzymes to water-insoluble polymeric supports such as cellulose dextran derivatives, polyacrylamide and porous glass Diffusion problems and steric hindrance are two main factors affecting the application of such supports. The introduction of soluble polymers for immobilization purposes overcomes these difficulties to a greater extent. These soluble enzyme derivatives were synthesized in order to increase the effective molecular size of parent en mes this would rmit the use of ultrafiltration without any los of the enzyme. O NeiD etal. immobilized the enzyme chymotrypsin on soluble dextran for... 

Beaton, N.C., Ultrafiltration and reverse osmosis in the dairy industry—an introduction to sanitary considerations, J. Food Prot., 42, 584, 1979. 

Zumbusch P and Kulcke W. Use of alternating electrical fields as anti fouling strategy in ultrafiltration of biological suspensions Introduction of new experimental procedure for crossflow filtration. J Membr Sci 1998 142 75-86. 

Historically, direct procedures were too cumbersome, time-consuming, and expensive for use in a routine clinical laboratory. The introduction of very sensitive immunoassays for T4 and T3 combined with improvements in the dialysis or ultrafiltration of undiluted serum has allowed direct measurement of free thyroid hormones. Thus direct equilibrium dialysis and ultrafiltration methods are available for FT4 measurement. 

The introduction of gel permeation chromatography materials and ultrafiltration membranes has provided powerful techniques which give very good fractionations on the basis of molecular size. Both techniques are now widely used, and although less popular, centrifugation is available as an alternative independent technique. 

Moreover, ultrafiltration membranes derived from polyaramide were successfully modified by electron beam irradiation [63]. As displayed in Fig. 9, an increase in retention capability without any change in permeate flux was achieved, due to chemical reactions leading to crosslinks and to the introduction of hydrophilic groups into the polymer backbone. 

When, to satisfy ultrafiltration, nanofiltration, or gas separation requirements, the required pore size is under 0.1 pm, the ceramic powder approach is no longer viable. Indeed, individual particles yielding pore diameters smaller than 0.1 pm cannot be handled by powder processing. In fact, particles of this type enter the category of colloids and must be maintained as a stable suspension during the process. As indicated in the introduction, the sol-gel method is a very suitable way to produce mesoporous and nanoporous membranes. The latter is elaborated in the next section. 

In this thesis, the initial chapters provide an introduction with a description of the organics (Chapter 2), the membrane processes (Chapter 3), and a general materials and methods section (Chapter 4). This is followed by the results of the different processes, microfiltration (Chapter 5), ultrafiltration (Chapter 6),... 

Separation processes such as ultrafiltration and micro filtration use porous membranes which allow the passage of molecules smaller than the membrane pore size. Ultrafiltration membranes have pore sizes from 0.001 to 0.1 )im while micro filtration membranes have pore sizes in the range of 0.02 to 10 im. The production of these membranes is almost exclusively based on non-solvent inversion method which has two essential steps the polymer is dissolved in a solvent, cast to form a film then the film is exposed to a non-solvent. Two factors determine the quality of the membrane pore size and selectivity. Selectivity is determined by how narrow the distribution of pore size is. In order to obtain membranes with good selectivity, one must control the non-solvent inversion process so that it inverts slowly. If it occurs too fast, it causes the formation of pores of different sizes which will be non-uniformly distributed. This can be prevented either by an introduction of a large number of nuclei, which are uniformly distributed in the polymer membrane or by the use of a solvent combination which regulates the rate of solvent replacement. 

The hydrophilization of poly(ether sulfone) surfaces used for the production of ultrafiltration membranes for hemodialysis is of special interest Poly(ether sulfone) is a chemically inert and highly thermostable polymer showing a hydrophobic surface which leads to high fibrinogen adsorption and subsequent thromboembolization [111]. This effect is generally avoided by non-desirable heparin doses. The hydrophilization of poly(ether sulfone) surfaces by plasma-induced graftcopolymerization and the introduction of a hydrogel layer without... 

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