Glass fibers zirconia-silica

Inorganic membranes, usually appUed when high temperatures or chemically active mixtures are involved, are made of ceramics [171,172], zirconia-coated graphite [173],silica-zirconia [174],zeolites [168], or porous glass [175] among others [176]. Ceramic membranes are steam sterilizable and offer a higher mechanical stability [134], thus they may be preferably used in aseptic fermentations, since some hollow fibers are only chemically sterilizable and not very suitable for reuse. Composite materials, in which glass fiber filters are used as support for the polymerization of acrylamide monomers, were developed for the hydrolysis of penicillin G in an electrically immobilized enzyme reactor. By careful adjustment of the isoelectric point of amphoteric membranes, the product of interest (6-aminopenicillanic acid) was retained in an adequate chamber, adjacent to the reaction chamber, while the main contaminant (phenyl acetic acid), was collected in a third chamber [120]. 

Their resistance to aikaline media exceeds that of commercially available AR silicate glass fibers (Chapter 6) having a zirconia content of up to 15% [20]. Hydroxyl-free quaternary calcium aluminate glass fibers (Figure 9), e.g., non-silica fibers containing 46.2% AI2O3 -36.0% CaO - 4.0% MgO -13.8% BaO, afford sapphire-like infrared transmission properties. 

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