Membrane review

In this chapter, membrane filtration in water treatment is reviewed. The aim is to assess the current status and reveal gaps in knowledge firom the wealth of literature. The background on models and principles is summarised for the relevant processes microfiltration (MF), ultrafiltration fUFJ, and nanofiltration (NF). Reverse osmosis is brifily considered to put NF, which is often described as a process in between UF and RO, in perspective. 

After a brief description of membrane materials, membrane rejection and fouling will be addressed. Both rejection of and fouling ly natural organics and inorganic colloids, will be a major focus of this work. A further issue is the characterisation of clean andfouled membranes as well as fouling control. 

The last sections describe membrane application issues in water treatment. The processes have been compared in terms of their volume of application and recent ffowth. This is obviously linked to treatment cost, an issue which will also be addressed hriefy. Problems which have arisen in previous pilot plant orfull scale studies will he part of the fouling studies in this thesis, where effects can he investigated on a smaller scale. Issues of concentrate disposal or treatment and membrane integrity are not discussed in this review. The concluding remarks address research needs and plans for this project. 

There are many processes available for water treatment. Process selection depends on the required water quality, and therefore which solutes or particles are to be retained. Of course the treatment cost also plays a major role in process selection. Unfortunately, environmental criteria - such as reduction of chemical addition or alternative operation modes, which allow the use of alternative energies — are, at best, only indirecdy considered in cost evaluations which precede process selecdon. 

Conventional physico-chemical treatment involving addition of coagulants and sand filtration, competes with membrane separation processes, but often fails in the treatment of waters containing large amounts of natural organic matter. In Table 3.1, an overview of common processes as well as the sizes of solutes and particles of interest is presented. 

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Finally, during budding, HIV-1 may also incorporate into its membrane envelope a variety of different molecules, including proteins that may subsequently interact with their counterparts on the host cell membrane (reviewed in ref. 192), resulting in intracellular signaling and facilitation of virus fusion (193,194). However, the incorporation of cell membrane-derived molecules does not appear to be an absolute requirement for virus entry (195), indicating the leading role of CD4 and the coreceptor for any such mechanism. However, this phenomenon may account for lower levels of inhibition when the effects of mutant CD4 and/or chemokine receptor are studied. 

An important function of the PDZ domains hes in the formation of macromolecular associates at the cell membrane (review Pawson and Scott, 1997). PDZ proteins can also provide a framework for clustering of proteins, such as ion channels, at the cell membrane and they may help to recruit proteins into membrane-bound macromolecular complexes. 

The function of spectrin superfamily proteins is particularly evident when taken in context of their cellular localization. They often form flexible links or structures that allow interactions with the cellular cyto-skeletal architecture and the membrane. In both spectrin and dystrophin, such a function is performed, but the spectrin repeats of these molecules are also able to interact with actin and contribute to binding. A portion of the dystrophin rod domain that spans residues 11-17 contains a number of basic repeats that allow a lateral interaction with filamentous actin (Rybakova et al., 2002). The homologous utrophin can also interact laterally with actin. This interaction is distinct from that of dystrophin, as the utrophin rod domain lacks the basic repeat cluster and associates with actin via the first ten spectrin repeats (Rybakova et al., 2002). /3-Spectrin also exhibits an extended contact with actin via the first spectrin repeat. In this situation, it was found that the extended contact increased the association of the adjacent ABD with actin (Li and Bennett, 1996). In conjunction with this interaction, it has been found that the second repeat is also required for maximal interaction with adducin (Li and Bennett, 1996), a protein localized at the spectrin-actin junction that is believed to contribute to the assembly of this structure in the membrane skeletal network (Gardner and Bennett, 1987). In the erythrocyte cytoskeletal lattice, /3-spectrin interacts with ankyrin, which in turn binds to the cytoplasmic domain of the membrane-associated anion exchanger. This indirect link to the cellular membrane occurs via repeat 15 of /3-spectrin (Kennedy et al., 1991) and is largely responsible for the attachment of the spectrin-actin network to the erythrocyte membrane (reviewed in Bennett and Baines, 2001). A much larger number of direct links to transmembrane proteins have been determined for the spectrin repeats of o-actinin (reviewed in Djinovic-Carugo et al, 2002). 

Keywords. Polyimides, Polydimethylsiloxane, Block or segmented copolymers, Synthesis Characterization, Physical Behavior, Adhesion, Membranes, Review... 

Both target peptides and signal peptides direct the precursor to the proper membrane by interaction with membrane-associated factors. In yeast, target peptides interact directly with functionally redundant receptors in the mitochondrial outer membrane (reviewed in Baker and Schatz,... 

Wang X and Quinn PJ (2000) The location and function of vitamin E in membranes (review). Molecular Membrane Biology 17, 143-56. 

T.L. Steck, Organization of Proteins in Human Red Blood Cell Membrane - Review , J. Cell Biol., 62, 1 (1974)... 

Like ASLV, HIV has a multistep mechanism for activation of membrane fusion. However, low pH is not required for HIV entry, and the virus instead uses a series of distinct interactions with components of the target membrane (reviewed in Dorns and Trono, 2000). The first interaction is with the CD4 protein. This binding event enables a subsequent contact between the HIV SU subunit gpl20 and a molecule of the chemokine receptor family (reviewed in Choe et al, 1998). It is this second interaction with molecules termed coreceptors that activates the membrane fusion potential of the TM subunit gp41 (reviewed in Berger et al, 1999). 

Cleavage of a cell into two equal parts is a dramatic event that requires coordinated generation of force around the entire perimeter of the cell (Fig. 5a). As a clue to how this might be achieved, a filamentous structure was shown by electron microscopy to lie at the cleavage furrow, just below the plasma membrane (reviewed in Reference 47). These filaments, distinct from microtubules, were called microfllaments. A key... 

However, the details of the molecular mechanism of redox-linked proton translocation are still largely unknown, not only for cytochrome oxidase but for the entire respiratory chain. In considering various possibilities it is important to distinguish between basically different elementary steps of the process. Proton conduction through the protein is but one such element. Several possible mechanisms have been proposed for this function, based on conduction along hydrogen-bonded networks of amino acid residues within the membrane (reviewed in Ref. 8). In redox-linked... 

Separation of organic solvents Methacrylate polymer membrane Review (Japanese) [101]... 

Separation methods for High surface area membrane Review with 32 references [103]... 

Figoli A, Sager WFC, and Mulder MHV. Facilitated oxygen transport in Uquid membranes Review and new concepts. J Mem Sci, 2001 181(1) 97-110. 

K. Uezu, M. Goto, S. Furusaki, Required properties for functional monomers to produce a metal template effect by a surface molecular imprinting technique, Macromolecules, 1999, 32, 1236 S.A. Piletsky, I.A. Panasyuk, E.V Pletskaya, I.A. Nicholls, M. Ulbricht, Receptor and transport properties of imprinted polymer membranes - review, J. Membr. Sci., 1999, 157, 263. 

Lin J, Kumakiri 1, Nair BN, Alsyouri H. Microporous ceramic membranes review. Sep Purif Methods. 2002 31(2) 229. 

Nair BN, Okubo T, Nakao S. Structure and separation properties of silica membranes review. 

Separation of organic-organic mixture. Various organic and inorganic membranes Review on current scientific and technological factors governing separation of organic mixtures. [193]... 

Stem Cells Ascend from the bottom of the Lieberktihn crypt to renew themselves and release somatic cells to function as epithelial cells of the mucous membrane (reviewed in Table I). 

We have reviewed safety improvements of organic electrolytes by adding flame retardants, and ILs have also been discussed. A more radical solution would be replacing liquid organic electrolytes with solvent-free lithium conductive-membranes reviewed in [196,197]. The most promising options have been briefly reviewed in [198], in particular membranes based on homopolymers, such as poly(ethylene oxide) hosting a lithium salt. However, the conductivity of these polymers is still too low to make them suitable to batteries operating at ambient temperature [199]. 

The handbook chapter Porous Silicon Membranes reviews the different fabrication routes and applications of mesoporous and macroporous silicon membranes. Among inoiganic membrane materials, porous silicon has been the most studied for immunoisolation (macroencapsulation). Desai and Ferrari developed a micro fabrication technique to produce controlled slit pores in 0.5-5 pm-thick Si membranes (see Fig. 2) (Leoni and Desai 2004 Desai et al. 1998, 2000a, b, 2004). The width of these pores (constant length of 45 pm) can be varied from 7 to 100 nm with less than 5 % of variation. The pores are produced by dissolution of a thermally grown sacrificial silicon oxide layer. These membranes present a porosity of 1 % (Leoni and Desai 2004 Desai et al. 2000b). 

Aimers, W. (1978). Gating currents and charge movements in excitable membranes. Review of Physiology, Biochemistry and Pharmacology 96-190. 

Silvius JR, Nabi IR (2006) Fluorescence-quenching and resonance energy transfer studies of lipid microdomains in model and biological membranes (review). Mol Membr Biol 23 5-16... 

The hollow fibre membranes reviewed in the present work here are formed using the wet phase inversion process. The wet phase inversion process has been very well described by Strathmann." " In his work, Strathmann casts various polymer solutions onto glass plates and then immerses the cast film into a bath of precipitation fluid. This kind of precipitation is fast and a skinned membrane structure forms. The skin formation is explained by Strathmann on the basis of the concentration profiles of the polymer, solvent and the precipitant which occurred during the phase inversion process. 

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