Electrically conductive membranes

Ultrafiltration permselectivity of a ceramic membrane can be enhanced by applying an electric field to the surface of the electrically conductive membrane [Guizard et al., 1986a]. The electric field is created using two electrodes with the conductive membrane being the anode or cathode. Such conductive membranes can be prepared with the introduction of a proper amount of Ru02 to Ti(>2. 

In contrast to the caustic potash being used within alkaline systems, PEM electrolysis is equipped with an electrical conductive membrane (Fig. 12.1), which is suited to fulfill the very high requirements, for instance current density. This membrane constitutes furthermore the gastight separation between oxygen and hydrogen side and allows operation up to pressure levels of 100 bars and more. 

The cell membrane is an absolute necessity for life because by it the cell can control its interior by controlling the membrane permeability. If the membrane is destroyed, then the cell dies. The membrane is a layer that separates two solutions and forms two sharp boundaries toward them. The cell membrane consists of phospholipids that form a bilayer lipid membrane (BLM) approximately 7 nm thick (Figure 4.6). Each monolayer has its hydrophobic surface oriented inward and its hydrophilic surface outward toward the intracellular or extracellular fluids. The inside of such a bilayer is hydrophobic and lipophilic. A BLM is a very low electric conductivity membrane and is accordingly in itself closed for ions. It lets lipids pass but not water. However, water molecules can pass specialized membrane channels (cf. Chapter 5). The intrinsic conductance is on the order of 10 S/m, and a possible lipophilic ionic conductivity contribution cannot be excluded. 

Organic electrically conductive membranes such as 3-methyIPT syntheazed on porous polycarbonate microfilter membranes can be used for the separation of neutral solutes [242]. Such superthin membranes can also consist of a heterolayer polymer, 3-methylPT and poly(pyrrole) [243]. 

Electrochemically synthesized polypyrrole-enzyme membranes have been shown to be enzymatically active and electrically conductive. Membrane-bound GOD is electrochemically regenerated from the reduced form of GOD. The enzyme activity of membrane-bound ADH can be electrochemically regulated. 

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