Chemical modification of the membrane surface

The separation of proteins can be improved by chemical modification of the membrane surface [94]. Coating a Carbosep M5 membrane (10,000 D) with quaternized polyvinylimidazole raises the retention of tetracycline from 25% towards 76%. Unfortunately the flux declines at the same time from 321/m h to 7.61/m h. 

Often preventive measures may be taken to avoid fouling the membrane. Prefilters or screens can be used to remove large particles which block thin channels or accumulate in stagnant areas of the module. High cross-flow velocities tend to sweep deposits away. Low pressures avoid compaction of gels on the membrane. Some polymers have a higher susceptibility to fouling and chemical modification of the membrane surface can have a profound effect on the propensity to foul. 

Chemical modification of a membrane surface can be used in combination with spacers and periodic applications of bioacids [70]. The paper by Redondo, however, is short on specifics (e.g., details of chemical modification of aromatic polyamides membrane surface), and therefore not very useful to those looking for insights into membrane fouling. 

Transport of newly synthesized PE to the plasma membrane. When an ethanolamine precursor is used, the primary site of PE synthesis is the ER (Chapter 8). The appearance of newly synthesized PE at the external leaflet of plasma membrane has been determined using chemical modification of the cell surface with TNBS at reduced temperature (R. Sleight,... 

The chemical modification of the filler surface is frequently used to increase the affinity of the dispersed phase with the polymeric phase or with the solvent used to prepare the casting solution. The nature of the chemical moieties grafted depends on the features of the polymer or the solvent considered for the particular membrane preparation procedure, and either covalent or noncovalent bonds can be considered. 

MBfRs depend on the ability of microorganisms to attach to the membrane surface. Several researchers have modified membranes to promote microbial attachment and retention. The methods can be classified as chemical modification of the membrane material or addition of support material onto the membrane surface. 

However, other methods for the fabrication of MOF membranes are reported, such as chemical modification of the support surfaces with self-assembled monolayer [60]. 

The acceptor-doped perovskites (general formula of ABOs-a) have shown much promise as MIECs. Much attention has been focused on these versatile metal oxides as they exhibit catalytic activity [24] and therefore their use in some applications can avoid the need for catalytic modification of the membrane surface. This activity has meant that MIECs can be used as electrode materials in solid-oxide fuel cell systems for the reduction of oxygen simultaneously, this inherent catalytic activity means that problems with chemical stability can arise. 

Modification of the membranes affects the properties. Cross-linking improves mechanical properties and chemical resistivity. Fixed-charge membranes are formed by incorporating polyelectrolytes into polymer solution and cross-linking after the membrane is precipitated (6), or by substituting ionic species onto the polymer chain (eg, sulfonation). Polymer grafting alters surface properties (7). Enzymes are added to react with permeable species (8—11) and reduce fouling (12,13). 

In other words, it proves that it is possible to design any experiment in such a way that it exceeds the limit of its validity. Both the adhesion and the Severinghaus effect can be mitigated by proper design of the membrane (Li et al., 1988) or by chemical modification of the surface of the dielectric. 

The use of Schott s porous glass membremes (pore sizes from 10 to 90 nm) in the separation of proteins with molecular weights from 14,400 to 450,000 is illustrated by Langer and Schnabel [85] who show a decrease in retention with increasing pore size for different proteins. Due to the chemical nature of the membrane material, it lends itself to surface modifications, including the coupling of enzymes or the attachment of micro-organisms. 

The surface modification can aim at different goals for example, the purpose could be the achievement of a superior chemical compatibility between the two phases through the addition of bridging agents [82]. The modification of the CNTs surface is frequently reported to increase their affinity with polymer solution. One example has been reported in the literature to obtain MMMs of multiwalled carbon nanotubes (MWNTs) in hydrophilic polymer blends for the synthesis of gas separation membranes. Acidification [62] and amino functionalization [56] of the fillers have been performed to increase their dispersability in an aqueous-based casting solution and to offer a reactive moiety for further crosslinking with polymer chains. 

Since it is the surface of solid silica that attracts and disrupts cell membranes and causes silicosis, any covering or chemical modification of the surface to reduce the adsorption of components of cell membranes, especially phosphatidyl choline, will also prevent the initiation of silicosis. This has been accomplished in three general... 

Surface mobility of adsorbed hydrogen in the catalytic layer favors proton migration between membrane and electrodes and improves Pt utilization. Mobility is usually associated with proton acceptor groups in the vicinity of catalyst nanoparticles. The chemical modification of the surface of carbon supports with proton acceptors has been proposed as a promising strategy to improve the catalytic layer performance [1-4]. 

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