Cross-flow ultrafiltration

Figure 3. Oligouronides evolution in a reactor without cross-flow ultrafiltration membrane, (a) Native Rh. nigricans endoPG. (b) Pasteurised Rh. nigricans endoPG.

Nanoparticles may be purified from the ME constituting components (surfactant and organic phase) via freeze-dr5nng [18] or a cross-flow ultrafiltration [19]. However, the use of isolated nanoparticles as the catalysts requires their separation from the reaction mixture after reaction via ultrafiltration. 

Cross-flow is the usual case where cake compressibility is a problem. Cross-flow microfiltration is much the same as cross-flow ultrafiltration in principle. In practice, the devices are often different. As with UF, spiral-wound membranes provide the most economical configuration for many large-scale installations. However, capillary devices and cassettes are widely employed, especially at smaller scale. A detailed description of cross-flow microfiltration had been given by Murkes and Carlsson [Crossflow Filtration, Wiley, New York (1988)]. 

Guo LD, Santschi PH (1996) A critical evaluation of the cross-flow ultrafiltration technique for sampling colloidal organic carbon in seawater. Marine Chem 55 113-127 Guo LD, Wen LS, Tang DG, Santschi PH (2000) Re-examination of cross-flow ultrafiltration for sampling aquatic colloids evidence from molecular probes. Marine Chem 69 75-90 Guo LD, Hunt BJ, Santschi PH (2001) Ultrafiltration behavior of major ions (Na, Ca, Mg, F, Cl, and SO4) in natnral waters. Water Res 35 1500-1508... 

Bowen, W. R. and Williams, P. M. Chem. Eng. Sci. 56 (2001) 3083. Prediction of the rate of cross-flow ultrafiltration of colloids with concentration-dependent diffusion coefficient and viscosity-theory and experiment. 

This technique of MEUF has also been successfully employed for the recovery of thuringiensin [258], removal of cresols [262], extraction of chromate anion [257], removal of dissolved organic pollutants [256], removal of -alcohols [263],preconcentration and removal of iron [260], and preconcentration of aniline derivatives [261].Kandori and Schechter [264] have given a detailed account of selecting surfactants for MEUF. The design characteristics of micellar enhanced utrafilters and cross-flow ultrafiltration of micellar surfactant solutions have been described by Markets et al. [265]. 

Guo, L., and Santschi, P.H. (1996) A critical evaluation of the cross-flow ultrafiltration techniques for sampling colloidal organic carbon in seawater. Mar. Chem. 55, 113-127. 

Rodriguez C, Sarrade S, Schrive L, Dresh-Bazile M, Paolucci D, and Rios GM. Membrane fouling in cross-flow ultrafiltration of mineral oil assisted by pressurized CO2. Desalination 2002 144 173-178. 

Elmaleh S and Ghaffor N, Cross-flow ultrafiltration of hydrocarbon and biological solid mixed suspensions, J. Membr. Sci. 1996 118 111-120. 

Cheng TW, Influence of inclination on gas-sparged cross-flow ultrafiltration through an inorganic tubular membrane, J. Membr. Sci. 2002 196(1) 103-110. 

Danckwerts P.V., Significance of liquid film coefficients in gas absorption. Industrial Engineering and Chemistry 43 1951 460-1470. Denisov C.A., Theory of concentration polarization in cross-flow ultrafiltration Cel-layer model and osmotic-pressure model. Journal of Membrane Science 91 1994 173-187. 

Membrane modules can be operated in the dead-end or cross-flow modes (see Figure 18.8). Dead-end ultrafiltration is used mostly for laboratory-scale applications and industrial ultrafiltration processes are usually carried out in the cross-flow mode. The main advantage of cross-flow ultrafiltration is the lower extent of concentration polarization. The cross-flow mode also allows recirculation of the retentate stream to the feed tank followed by its mixing with fresh feed that leads to several operational advantages. 

Cui, ZF and Wright, KIT, Gas-liquid 2-phase cross-flow ultrafiltration of BSA and dextran solutions, J. Membr. Sci., 90, 183, 1994. 

Clarification of rough beer, vinegar and pasteurization of clarified beer by cross-flow ultrafiltration are also very common processes utilizing hollow fiber ultrafiltration. As seen in Table 1, an important number of membrane manufacturers specialize in medical and pharmaceutical applications. In pharmaceutical and biotechnology industries, hollow fiber membranes are used for the concentration, separation, and purification of physiological activators such as antibiotics, vaccines, enzymes, proteins and peptides, as well as blood purification (hemofiltration). As a physical barrier for bacteria and viruses, membranes are also a popular option for the production of purified water for hospitals and pharmacies. 

Cui ZF, and Wright KIT, Flux enhancement with gas sparging in downwards cross-flow ultrafiltration Performance and mechanisms, J. Membr. Sci. 1996 117 109-116. 

It is further shown that the current practice of plotting permeate flux vs. AP in macromolecular cross-flow ultrafiltration may lead to serious misinterpretation of gel polarization. It is therefore recommended that solutions be studied in the unstirred... 

R. Kohl, G. Tomandl, A. Larbot, L. Cot and J. Gillot, Herstellung und Charakterisie-rung von keramischen Membranen aus Titanoxid zur Cross-Flow-Ultrafiltration nach dem Sol-Gel-Verfahren, Kurzreferate pp. 64-66, DKG-Jahrestagung, Bayreuth, 4.-7. Ok-tober 1992. 

A variety of spectroscopic techniques have been applied to DOC isolated from seawater by cross-flow ultrafiltration or adsorption onto XAD resins. The two techniques isolate very different organic fractions from seawater. Hydrophobic fractions (such as marine humic material) are isolated on XAD resins [48], whereas the organic matter extracted by ultrafiltration is retained primarily on the basis of its molecular size and shape [49], resulting in isolates rich in nitrogen and carbohydrates (polysaccharides). Nuclear magnetic resonance (NMR) spectroscopy has proven successful in distinguishing between the specific structures of XAD-bound humics and the carbohydrates concentrated into colloidal size fractions. 

Cheng, T. and Lin, C. T. (2004) A study on cross flow ultrafiltration with various membrane orientations. Separation and Purification Technology 39, 13-22. 

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