Diatomaceous earths

Diatomaceous earth, or DE, is the processed fossilized remains of marine and freshwater algae (diatoms). It is commonly used as a general filtration aid. Occasionally, DE may bleed through the filtration matrix, ending up in the wine. It can be readily identified by microscopic examination. 

Collect particulate material by either filtration or centrifugation. 

Diatomaceous earth (DE) is the processed fossilized remains of marine and freshwater algae called diatoms. Commonly used in the winery as a 

CAS [68855-54-9] an amorphous form of silica highly porous, absorbs water used to purify liquids, in the manufacture of firebrick and heat insulators, and in metal polishes. 

There is no adverse effect on the lungs. Under normal conditions of occupational exposures, any fibrogenic or toxic effecf is insignificanf. Silicosis observed in animals from infrafracheal insfillafion or inhalafion is aftribufed to fhe presence of crysfalline quarfz in diafomaceous earth. TLV-TWA 10 mg/m as total dust (ACGIH). 

Inhalation causes cough, dyspnea, black sputum, and fibrosis. TLV-TWA 2.5 mg/m (respirable dusf), 5.0 mg/m (folal dusf) (ACGIH), 15 mppcf (OSHA). 

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The addition of a Whatman filter tablet or of a little diatomaceous earth (Super Cel. etc.) assists in the filtration of the finely divided manganese dioxide. 

The most widely used particulate support is diatomaceous earth, which is composed of the silica skeletons of diatoms. These particles are quite porous, with surface areas of 0.5-7.5 m /g, which provides ample contact between the mobile phase and stationary phase. When hydrolyzed, the surface of a diatomaceous earth contains silanol groups (-SiOH), providing active sites that absorb solute molecules in gas-solid chromatography. 

More recently, solid supports made from glass beads or fluorocarbon polymers have been introduced. These supports have the advantage of being more inert than diatomaceous earth. 

Capillary columns are of two principal types. Wall-coated open tuhular columns (WCOT) contain a thin layer of stationary phase, typically 0.25 pm thick, coated on the capillary s inner wall. In support-coated open tuhular columns (SCOT), a thin layer of a solid support, such as a diatomaceous earth, coated with a liquid stationary phase is attached to the capillary s inner wall. 

Materials suitable as filter aids include diatomaceous earth, expanded perilitic rock, asbestos, ceUulose, nonactivated carbon, ashes, ground chalk, or mixtures of those materials. The amount of body feed is subject to optimisa tion, and the criterion for the optimisa tion depends on the purpose of the filtration. Maximum yield of filtrate per unit mass of filter aid is probably most common but longest cycle, fastest flow, or maximum utilisation of cake space are other criteria that requite a different rate of body feed addition. The tests to be carried out for such optimisation normally use laboratory or pilot-scale filters, and must include variation of the filtration parameters such as pressure or cake thickness in the optimisation. 

Pressing. There are a variety of fmit presses. Some presses are more suitable for one type of fmit than for others, but most can be used for any fmit with varying degrees of success. Some presses requite the use of a press aid such as diatomaceous earth or wood chips. Total juice yield from the original fmit defines press efficiency. Additional yield can be obtained by adding a small amount of water to the press cake and pressing again. 

Granulars are pelleted mixtures of toxicant, usually at 2.5 ndash 10%, and a dust carrier, eg, absorptive clay, bentonite, or diatomaceous earth, and commonly are 250 ndash 590 ]lni in particle size. They are prepared by impregnation of the carrier with a solution or slurry of the toxicant and are used principally for mosquito larviciding and soil appHcations. 

R. Patel and D. Clifford, Radium Removalfrom Water by Manganese Dioxide Adsorption and Diatomaceous Earth Filtration, NTIS PB92-115260/AS, Springfield, Va., 1992. 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

The use of fine particle size iasoluble material, or diatomaceous earth-based fluid stmctuting agents, ia the aqueous phase also stabilizes some emulsions. A recipe for an emulsion of a Hquid, nondiscoloring antioxidant (Naugawhite) is given below ... 

MicrocrystaUine Silicas. Various microcrystalline (cryptocrystalline) materials such as flint, chert, and diatomaceous earth are found ia nature (see Diatomite). These may arise from amorphous silica, often of biogenic origin, which undergoes compaction and microcrysta11i2ation over geologic time. 

Approximately 40% of synthetic amorphous siUca production is in Europe, followed by North America at 30%, and Japan at 12%. Although deposits of naturally occurring amorphous siUcas are found in all areas of the world, the most significant commercial exploitation is of diatomaceous earth in industrialized countries (see Diatomite). This is because of the high cost of transportation relative to the cost of the material. Worldwide manufacturers of amorphous siUca products are Hsted in Table 2. 

Hydrogenation. Gas-phase catalytic hydrogenation of succinic anhydride yields y-butyrolactone [96-48-0] (GBL), tetrahydrofiiran [109-99-9] (THF), 1,4-butanediol (BDO), or a mixture of these products, depending on the experimental conditions. Catalysts mentioned in the Hterature include copper chromites with various additives (72), copper—zinc oxides with promoters (73—75), and mthenium (76). The same products are obtained by hquid-phase hydrogenation catalysts used include Pd with various modifiers on various carriers (77—80), Ru on C (81) or Ru complexes (82,83), Rh on C (79), Cu—Co—Mn oxides (84), Co—Ni—Re oxides (85), Cu—Ti oxides (86), Ca—Mo—Ni on diatomaceous earth (87), and Mo—Ba—Re oxides (88). Chemical reduction of succinic anhydride to GBL or THF can be performed with 2-propanol in the presence of Zr02 catalyst (89,90). 

Filtration. Any type of clarification is foUowed by filtration through leaf-type vertical or horizontal pressure filters. Carbonatated Hquors, containing calcium carbonate, may require addition of diatomaceous earth as a filter precoat. Phosphatated Hquors are generally filtered with the addition of diatomaceous earth as precoat and body feed. 

Manufacture. Small cylinders of hydrogen sulfide are readily available for laboratory purposes, but the gas can also be easily synthesized by action of dilute sulfuric or hydrochloric acid on iron sulfide, calcium sulfide [20548-54-3], zinc sulfide [1314-98-3], or sodium hydrosulfide [16721 -80-5]. The reaction usually is mn in a Kipp generator, which regulates the addition of the acid to maintain a steady hydrogen sulfide pressure. Small laboratory quantities of hydrogen sulfide can be easily formed by heating at 280—320°C a mixture of sulfur and a hydrogen-rich, nonvolatile aUphatic substance, eg, paraffin. Gas evolution proceeds more smoothly if asbestos or diatomaceous earth is also present. 

Catalysts. Commercial sulfuric acid catalysts typically consist of vanadium and potassium salts supported on sUica, usually diatomaceous earth (see Diatomite). Catalyst peUets are available in various formulations, shapes, and sizes depending on the manufacturer and the particular converter pass in which they are to be used. A detailed discussion of oxidation catalysts for sulfuric acid production is available (107). 

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