Hollow-fibre ultrafiltration

Christl, I., Knicker, H., Koegel-Knabner, I., and Kretzschmar,R. (2000). Chemical heterogeneity of humic substances Characterization of size fractions obtained by hollow-fibre ultrafiltration. Euro J. Soil Sci. 51,617-625. 

Ultrafilters can be used to permit sequential washing and filtering, after which the filter cake is redispersed into suspension, or continuous hollow-fibre ultrafiltration can be used to accomplish the same result (see Figure 7.6). 

In order to obtain a sufficiently large membrane area on an industrial scale, hollow fibre ultrafiltration modules are applied (similar types to those used for protein purification). Since the concentration of NAD(H) does not change in the steady state and there is no NAD(H) in the entrance or exit flow, it becomes clear that the actual concentration of pyruvate in the reactor is equal to the concentration in the feed. Since there is a non-zero concentration of pyruvate in the reactor (and in the exit flow), some pyruvate has to be added to the reactor continuously in order to keep the reaction going. The rate equations of both reactions are required to calculate the precise rate of pyruvate addition. 

Manno, P. Moulin, P. Rouch, J.C. Clifton, M. Aptel, P. Mass transfer improvement in helically wound hollow-fibre ultrafiltration modules bentonite and yeast suspensions. Sep. Purif Tech. 

Minegishi, S., Jang, N.-Y., Watanabe, Y., Hirata, S., and Ozawa, G. (2001). Fouling mechanism of hollow fibre ultrafiltration membrane with pre-treatment by coagulation/sedimentation process. 

Soybean is an important source of protein, and the process to recover the protein and fat requires the removal of undesirable compounds. Traditional removal methods include extraction, heat treatment and centrifugation to separate the protein and fat from these compounds. Hollow fibre ultrafiltration modules are used to recover full fat soy protein concentrates and soy isolates. 

Membrane equipment for industrial scale operation of microfiltration, ultrafiltration and reverse osmosis is supplied in the form of modules. The area of membrane contained in these basic modules is in the range 1-20 m2. The modules may be connected together in series or in parallel to form a plant of the required performance. The four most common types of membrane modules are tubular, flat sheet, spiral wound and hollow fibre, as shown in Figures 8.9-8.12. 

Optimal fermentation parameters have been well established and air-lift, stirred tank, and hollow fibre systems have all been used. At commercial scale, fermentation volumes in excess of 1000 litres can be used, which can yield 100 g or more of final product. While hybridoma growth is straightforward, production levels of antibody can be quite low compared with ascites-based production systems. Typically, fermentation yields antibody concentrations of 0.1-0.5 mg/ml. Removal of cells from the antibody-containing media is achieved by centrifugation or filtration. An ultrafiltration step is then normally undertaken in order to concentrate the filtrate by up to 20-fold. 

B. Baum, W. Holley, Jr and R.A. White, Hollow Fibres in Reverse Osmosis, Dialysis, and Ultrafiltration, in Membrane Separation Processes, P. Meares (ed.), Elsevier, Amsterdam, pp. 187-228 (1976). 

A third general approach to encapsulation involves the use of permselective membrane devices of the types employed in ultrafiltration and nanofiltration of aqueous solutions, especially those devices that employ the membrane in the form of hollow fibres. In effect, the enzymes are retained within a macrocapsule. An aqueous solution of the soluble enzyme or whole cells is contained on the retentate side of the membrane, while a solution containing the substrates is supplied... 

Bellara, S.R. Cui, Z.F. Pepper, D.S. Gas sparging to enhance permeate flux in ultrafiltration using hollow fibre membranes. J. Membr. Sci. 1996, 121, 175-184. 

Figure 2.16 Ultrafiltration of cathodic paint using charged membranes (X1/X2) and a standard hollow-fibre membrane element. Source Romicon.

Ishihara et al (1991) designed a different method. The use of a suction filter unit and a reservoir tank that is constantly stirred enables the removal of the lignin-rich build-up. The hydrolysis products can then be removed by an ultrafiltration membrane unit. According to Henley et al (1980), the efficiency of the hydrolysis process can be improved by the addition of a ultrafiltration membrane stirred cell or a hollow-fibre cartridge into the CSTR-UF and CSTR-HC systems. 

The filtration apparatus was composed of a feed tank, a pump, an ultrafiltration cartridge and pressure gauges for feed, reteiitate and permeate. The membranes (table I) were polysulfone (Polymem and Pall) or cellulose acetate (Amicon) with a molecular weight cut-off ranging between 1 kDa and 50 kDa. The module was a flat sheet cassette (Pall) or hollow fibres (Amicon and Polymem). 

Cabassud, C., Laborie, S. and Laine, J. M. (1997). How slug flow can improve ultrafiltration flux in organic hollow fibres. J. Membr. Sci. 128, 93-101. 

Guigui, C., Mougenot, M., and Cabassud, C. (2003). Air sparging backwash in ultrafiltration hollow fibres for drinking water production. Water Sci. Technol Water Supply 3(5), 415-422. 

Qin, J. J., and Chung, T. S. (1999). Effect of dope flow rate on the morphology, separation performance, thermal and mechanical properties of ultrafiltration hollow fibre membranes. J. Membr. Sci. 157, 35. 

M.R. Moghareh Abed, S.C. Kumbharkar, Andrew M. Groth, and K. Li, Ultrafiltration PVDF hollow fibre membranes with interconnected bicontinuous structures produced via a single-step phase inversion technique. Journal of Membrane Science 407-408 (2012) 145-154. 

The book, Hollow Fibers (Scott, 1981) is an excellent practical source for details about the large-scale manufacture of hollow fibers. The effect of spinning parameters on both the macroscopic dimensions and permeation performance of polysulfone ultrafiltration hollow fibre membranes has been studied by several people (Kim et al., 1995, Liu et al., 1992, McKelvey et al., 1997, and Lee et al., 1995). The latter paper uses a factorial design to study the effects of various spinning parameters, and gives optimal spinning conditions for ultrafiltration performance. 

Two other major factors determining module selection are concentration polarisation control and resistance to fouling. Concentration polarisation control is a particularly important issue in liquid separations such as reverse osmosis and ultrafiltration. Hollow-fine-fibre modules are notoriously prone to fouling and concentration polarisation and can be used in reverse osmosis applications only when extensive, costly feed solution pretreatment removes all particulates. These fibres cannot be used in ultrafiltration applications at all. 

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