Inorganic filters

Polarized light—Is used if one of the polymer phases is crystalline or for agglomeration of inorganic filters, (e.g., nylon/EP blends and fillers such as talc. (Figure 4)... 

Maske, H., and Garcia-Mendoza, E. (1994). Adsorption of dissolved organic matter to the inorganic filter substrate and its implication for uptake measurements. Appl. Environ. Microbiol. 60, 3887-3889. 

II. THE CURRENT MARKET FOR HIGH-TEMPERATURE INORGANIC FILTERS... 

The use of porous inorganic filters for high-temperature applications is meeting with increasing interest [12,13J. Almost an entire book has recently been dedicated to this topic... 

Table 1 Commercial Inorganic Filters Types and Application Fields...

Pressurized fluidized-bed combustion (PFBC) of coal This is probably the most promising application field for inorganic filters, despite the fact that only a few large-scale examples of application have been successfully tested in very recent years [14]. Dust is removed just at the outlet of the boiler, allowing heat recovery from cleaned gases. 

For deeper insight into the applications of high-temperature filter media, the book by Clift and Seville [14] is recommended, and particularly the review by Bergmann, from Filter Media Consulting Inc. (La Grange, Georgia), therein included [15]. Section V of this chapter will discuss the new application opportunities allowed by catalytic activation of the above inorganic filters. 

A major alternative to direct flow membrane filtration is depth filtration, in which particles are removed throughout the filtration matrix rather than just at the membrane surface, by various mechanisms such as size exclusion, electrostatic, and hydrophobic interactions. Depth filters are typically composed of a bed of cellulose or polypropylene fibers together with an inorganic filter aid such as diatomaceous earth and a binder to form a filter sheet. The filter aid imparts the matrix very high surface areas and plays an important role in increasing both retention and the capacity. Depth filters can also have an electrostatic charge usually associated with the binder polymer. 

The use of asbestos has been greatly diminished because of its identification with health hazards. There have been proposed replacement materials such as the Zeta Plus filter media from the AMF Cuno Division, consisting of a composite of cellulose and inorganic filter aids that have a positive charge and provide an electrokinetic attraction to hold colloids (usually negatively charged). These media therefore provide both mechanical straining and electrokinetic adsorption. 

Some polymeric (PVDF or PTFE) and most Inorganic filters. 

Centrifugation is often followed by depth filtration. Alternatively, several depth filtration steps can be employed for clarification instead of centrifugation, especially for bench-, pilot-, or smaller commercial-scale applications [133]. Within depth filters, the particles are trapped in the internal matrix of the packed, porous material having a void volume of up to 85%. They are typically composed of cellulose fibers, inorganic filter aids such as diatomaceous earth, inorganic charged resin binders, and synthetic polymers. As the retention mechanism of depth filters is not absolute, some particles will get through, and it is not possible to define a minimum particle size that will be held back. Therefore, an additional membrane... 

Ceramic membranes impregnated with crosslinked silylated CD polymers, i.e. organic-inorganic filters were investigated for removal of some organic pollutants from water [59]. It was established that they remove polycyclic aromatic hydrocarbons PAH, the monocyclic aromatic hydrocarbons, trihalo methanes, methyl-f-butyl ether and pesticides. Trihalomethanes are disinfection by-products, they (especially dibromochloromethane) increase the risk of cancer. The pesticides simazine and atrazine are drinking water pollutants. 

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