Ultrafiltration systems

Ultrafiltration of micellar solutions combines the high permeate flows commonly found in ultrafiltration systems with the possibility of removing molecules independent of their size, since micelles can specifically solubilize or bind low molecular weight components. Characteristics of this separation technique, known as micellar-enhanced ultrafiltration (MEUF), are that micelles bind specific compounds and subsequent ultrafiltration separates the surrounding aqueous phase from the micelles [70]. The pore size of the UF membrane must be chosen such, that the micelles are retained but the unbound components can pass the membrane freely. Alternatively, proteins such as BSA have been used in stead of micelles to obtain similar enan-tioselective aggregates [71]. 

Choo KH, Choi SJ, Hwang ED (2007) Effect of coagulant types on textile wastewater reclamation in a combined coagulation/ultrafiltration system. Desalination 202 262-270... 

Comparison between the inventories in the collected fractions (the colloidal and ultrafiltered fractions) and in the starting sample often indicate that there are losses of nuclides on to the ultrafiltration cartridge. These are largely recovered by subsequent acid rinses of the ultrafilters and filtration system. It is not clear whether the recovered abundances should be considered part of the colloids retained by the filter, or solutes that have adsorbed in the system (Gustafsson et al. 1996 Andersson et al. 2001), even though test experiments with colloidally-bound " Th showed significant losses in the ultrafiltration system (Baskaran et al. 1992.)... 

Installation of an ultrafiltration system that recovers 30 kg/d (65 lb/d) of waste oil and purifies 1135 kg/d (2500 lb/d) of alkaline cleaning solution for reuse, which resulted in a reduction of 5-day biochemical oxygen demand (BOD5) loadings to the treatment system of 200 kg/ month (370 lb/month). This avoided the need for installation of additional treatment. 

Figure 6.6 ULtrafiLtration separates molecules based on size and shape, (a) Diagrammatic representation of a typical laboratory-scale ultrafiltration system. The sample (e.g. crude protein solution) is placed in the ultrafiltration chamber, where it sits directly above the ultrafilter membrane. The membrane, in turn, sits on a macroporous support to provide it with mechanical strength. Pressure is then applied (usually in the form of an inert gas), as shown. Molecules larger than the pore diameter (e.g. large proteins) are retained on the upstream side of the ultrafilter membrane. However, smaller molecules (particularly water molecules) are easily forced through the pores, thus effectively concentrating the protein solution (see also (b)). Membranes that display different pore sizes, i.e. have different molecular mass cut-off points, can be manufactured, (c) Photographic representation of an industrial-scale ultrafiltration system (photograph courtesy of Elga Ltd, UK)...

Diafiltration is a process whereby an ultrafiltration system is utilized to reduce or eliminate low molecular mass molecules from a solution and is sometimes employed as part of biopharmaceuti-cal downstream processing. In practice, this normally entails the removal of, for example, salts, ethanol and other solvents, buffer components, amino acids, peptides, added protein stabilizers or other molecules from a protein solution. Diafiltration is generally preceded by an ultrafiltration step to reduce process volumes initially. The actual diafiltration process is identical to that of ultrafiltration, except for the fact that the level of reservoir is maintained at a constant volume. This is achieved by the continual addition of solvent lacking the low molecular mass molecules that are to be removed. By recycling the concentrated material and adding sufficient fresh solvent to the system such that five times the original volume has emerged from the system as permeate, over 99... 

In a study of the bioaccumulation of metals as colloid complexes and free ions by the marine brown shrimp, Penaeus aztecus [29] the colloids were isolated and concentrated from water obtained from Dickinson Bayou, an inlet of Galveston Bay, Texas, using various filtration and ultrafiltration systems equipped with a spiral-wound 1 kDa cutoff cartridge. The total colloidal organic carbon in the concentrate was found to be 78 lmgdm 3. The shrimps were exposed to metals (Mn, Fe, Co, Zn, Cd, Ag, Sn, Ba and Hg) as radiolabelled colloid complexes, and free-ionic radiotracers using ultrafiltered seawater without radiotracers as controls. The experiments were designed so that the animals were exposed to environmentally realistic metal and colloid concentrations. 

Merck 60 F254 silica gel TLC plates Merck 60/230 00 and 60/40-63 mesh silica Millipore ultrafiltration system heating block shaker... 

Gaston County Filtration Systems. 1980. Gaston County ultrafiltration systems. Product brochure. 

The foregoing conclusions arising from earlier work (6b,10, 57,63-85) offer fruitful directions for a continuing program of research and development involving a wide variety of membrane materials, and reverse osmosis and ultrafiltration systems. 

Figure 3.41 Exploded view of a tubular ultrafiltration system in which 30 tubes are connected in series. Permeate from each tube is collected in the permeate manifold...

Ultrafiltration systems should never be taken off line without thorough flushing and cleaning. Because membrane modules are normally stored wet, the final rinse solutions should contain a bacteriostat such as 0.5% formaldehyde to inhibit bacterial growth. 

Figure 6.16 Horizontal DDS plate-and-frame ultrafiltration system. Courtesy of Alfa...

The simplest type of ultrafiltration system is a batch unit, shown in Figure 6.17. In such a unit, a limited volume of feed solution is circulated through a module at a high flow rate. The process continues until the required separation is achieved, after which the concentrate solution is drained from the feed tank, and the unit is ready to treat a second batch of solution. Batch processes are particularly suited to the small-scale operations common in the biotechnology and pharmaceutical industries. Such systems can be adapted to continuous use but this requires automatic controls, which are expensive and can be unreliable. 

Figure 6.21 Flow schematic of an electrocoat paint ultrafiltration system. The ultra-filtration system removes ionic impurities from the paint tank carried over from the chromate/phosphate cleaning steps and provides clean rinse water for the counter-current rinsing operation...

Figure 6.26 Flow schematic of a three-stage feed-and-bleed ultrafiltration system used to recover poly(vinyl alcohol) (PVA) sizing agents used in the production of cotton/synthetic blend fabrics [28]...

Microfiltration cross-flow systems are often operated at a constant applied transmembrane pressure in the same way as the reverse osmosis and ultrafiltration systems described in Chapters 5 and 6. However, microfiltration membranes tend to foul and lose flux much more quickly than ultrafiltration and reverse osmosis membranes. The rapid decline in flux makes it difficult to control system operation. For this reason, microfiltration systems are often operated as constant flux systems, and the transmembrane pressure across the membrane is slowly increased to maintain the flow as the membrane fouls. Most commonly the feed pressure is fixed at some high value and the permeate pressure... 

Methodological artefacts may arise for a number of reasons, most notably as a result of specific interactions of species with the filter membrane. Therefore the choice of the ultrafiltration system, the properties and influence of the membrane and the operating conditions must be carefully considered before the ultrafiltration technique is applied for the separation of different radionuclide species in environmental samples. 

Ultrafiltration system Without humic acid With humic acid ... 

Fermentation is typically conducted in dilute suspension culture. The low concentration in such systems limits reaction efficiency, and the presence of particulate and colloidal solids poses problems for product recovery and purification. By circulating the fermentation broth through an ultrafiltration system, it is possible to recover product continuously as they are generated while minimizing loss of enzyme or cells and keeping product concentration in the bioreactor below the self-inhibition level for the biocatalyst. This process is referred to as perfusion. As the ultrafiltration unit is part of the production process, the entire system is often considered a membrane reactor. 

Figure 431 ROCHEM ST module, a modified spiral wound module, showing a) a cross-section and b) the module within a pressure vessel housing. Courtesy ROCHEM Ultrafiltrations Systems GmbH.

Figure 16.4 Spiral wound ultrafiltration system. Courtesy of Koch Membrane Systems.

Al distribution in serum Ultrafiltration system Gel filtration column UF system washing with 10% HN03> 24 h membranes twice 0.1 mol L-1 NaOH gel filtration column 30 mol L-1 Na2C03) 48 h [89]... 

If automated 96 well plate ultrafiltration system is used, high throughput with sample handling by robotic system. 

The UF can either performed in a single ultrafilter unit or in a 96 well plate ultrafiltration system, latter in a semi-automatic high-throughput determination with sampling handling by a robotic system (Fung et al. 2003 Jordan et al. 2000). 

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