Filter contaminants

The old analytical chemistry literature is rich with methods involving homogeneous precipitation from solution, the purpose being to obtain dense (therefore easily filterable), contamination-free precipitates for purposes of analyses. The... 

Purpose of the screens is primarily twofold (1) to change the melt s spiraling motion, caused by the screw rotation and (2) to filter contaminants out of the melt. Most plastics contain contaminants and these particles can be conveniently removed by means of a screen placed after the extruder barrel and before the melt flow reaches the extrusion die. The simplest means for filtering plastic melts are woven wire mesh disks of about the same diameter as that of the extruder barrels. Several... 

Organic-membrane filters, such as cellulose-acetate and cellulose-nitrate filters, are often conditioned with organic surfactants to assist in wetting the filter. These surfactants will be leached from the filters, contaminate the... 

DISPOSAL AND STORAGE METHODS transmit used charcoal filters contaminated with carcinogen into properly labeled, sealed plastic bags collect waste liquids in secured, properly labeled containers or bottles once filled, bottles should be placed in sealed plastic bags store away from combustible materials and ignitions sources, since containers may explode in fire. 

Environment New membranes that can selectively filter contaminants nanostructured traps for removing pollutants from industrial effluents, characterization of the effects of nanostructures in the environment... 

Positive pressure plenums Contaminated Filtered Contaminated, but isolated... 

Aerobic bioreactors Inoculation cannot he used for the reactor/fermenter [contamination]. Product formation is inhibited [contamination]. Target product cannot he separated from contaminating species [contamination]. Fermentation broth cannot he filtered [contamination]. ... 

Since fuel cell performance cannot be totally recovered after SO poisoning, it is critical to prevent the cathode from SOx contamination in the air stream. Unfortunately, to date few studies have addressed the mitigation of SOx contamination at the cathode side. Two methods deal with air contamination of fuel cells increasing catalyst tolerance to impurities [45] and/or filtering contaminants from the air [46—48]. A Pt-Fe phosphate catalyst (Pt-FePO) was... 

Solid radioactive waste should be classified according to its nature and activity for instance, sludges, cartridge filters, contaminated equipment and components, ventilation filters and miscellaneous items (such as paper, plastic, towels) may be segregated in accordance with the type of treatment and conditioning process, such as compaction, incineration or immobilization. 

Screens are placed in the breaker plate to filter contamination from the polymer melt and to create pressure at the end of the extruder. The screen and breaker plate combination assist in providing thermal homogeneity in the polymer melt. Screens clogged with contaminants will cause high pressures at the end of the extruder reducing the extruder throughput. If the formulation contains fillers or fiber reinforcements all screens must be removed. 

Resin stagnation may be avoided by the use of a slightly conical or rounded nose screw tip. The type of the screw tip depends on whether a breaker plate is installed in the extruder. Although fluoropolymer extrusion does not require breaker plates, their installation can increase the backpressure for additional mixing. Breaker plates should be streamlined to avoid melt holdup and stagnation. Fluoropolymer screws do not need internal cooling. A screenpack consisting of one 120 mesh and two 80 mesh screens can be installed to filter contaminants out of the melt. 

The HEPA filter vacuum is more effective in filtering contaminants from air than standard vacuums because the HEPA filter is designed to retain particles of 0.3 micrometers in diameter with a minimum efficiency of 99.97 percent. Particles larger or smaller than this critical size are retained with a greater efficiency (see Chapter 9). 

High efficiency particle air (HEPA) filter (contamination control) See Mechanical filter. 

Mechanical filter (contamination control) A filter that prevents the passage of particles by having very small passages in the filter media. Example HEPA filter. 

Routine steam sterilization is a requirement for any system of sterile filtration, and is often carried out after each batch, according to laid down procedures, although this is not absolutely necessary, provided that the filter is kept pressurized, the relative humidity is kept below recommended levels, and a small bleed of air is allowed to flow continuously. It is important to note that the sterilizing steam must be saturated and free from any additives. Dirt in the system can cause filter contamination and hence increased pressure drop, and additives also have the same effect by crystallizing on the filter medium, which may also concentrate any possible chemical effects. 

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