Inorganic particulate contamination

Particulate contamination This class of contaminants includes organic, metallic solid, and inorganic solid contaminants. These contaminants are discussed in the following paragraphs. 

Whether the substrate is bulk Si or SOI, the most critical step in IC fabrication is the initial cleaning of the wafer. The RCA clean procedure is the industry standard, consisting of the following complex treatment to remove both organic and inorganic contaminants. It should be noted that these procedures are performed within a clean room, to avoid particulate contamination ... 

It is well known that small molecules can be removed from larger molecules using inorganic materials such as molecular sieves. However, this approach contaminates the polymer with inorganic particulates. The only literature teaching this approach are Russian patents claiming the addition of silica gel [27] and mont-morillonite clay [28] to absorb styrene from PS. The advances in nanocomposite technology in recent years may allow further development of this approach. 

Inorganic membranes can function as the capturing medium of clays, soils and other particulate contaminants in fluids. The inorganic membranes, such as silver membranes, containing the deposit of the contaminants or minerals are then used as the X-ray diffraction (XRD) substrate for material analysis of the particulates. In some cases, they are part of the established test procedures as a National Institute of Occupational Safety and Health (NIOSH) standard XRD substrate. 

Lipases are manufactured by fermentation of selected microorganisms followed by a purification process. The enzymatic interesterification catalysts are prepared by the addition of a solvent such as acetone, ethanol, or methanol to a slurry of an inorganic particulate material in buffered lipase solution. The precipitated enzyme coats the inorganic material, and the lipase-coated particles are recovered by filtration and dried. Various support materials have been used to immobilize lipases. Generally, porous particulate materials with high surface areas are preferred. Typical examples of the support materials are ion-exchange resins, silicas, macroporous polymers, clays, etcetera. Effective support functionality requirements include (i) the lipase must adsorb irreversibly with a suitable structure for functionality, (ii) pore sizes must not restrict reaction rates, (iii) the lipase must not contaminate the finished product, (iv) the lipase must be thermally stable, and (v) the lipase must be economical. The dried particles are almost inactive as interesterification catalyst until hydrated with up to 10% water prior to use. 

The products of incomplete combustion may be associated with particulate matter before their discharge into the atmosphere, and these may ultimately enter the aquatic and terrestrial environments in the form of precipitation and dry deposition. It is therefore essential to ensure total destruction of the contaminants, generally by raising the temperature. The spectrum of compounds that have been examined is quite extensive, and several of them are produced by reactions between hydrocarbons and inorganic sulfur or nitrogen constituents of air. Some illustrative examples involving other types of reaction include the following ... 

In air, most arsenic particulates consist of inorganic arsenic compounds, often as As+3. Burning of coal and arsenic-treated wood, and smelting of metals are major sources of atmospheric arsenic contamination (i.e., >1 pg/m3). In general, atmospheric arsenic levels are higher in winter, due to increased use of coal for heating (Pershagen and Vahter 1979). 

Inorganic and organic compounds are often present in the environment in complex forms. Levels of contaminating metals and molecules are variable, depending on the natural conditions and anthropogenic activities. The contaminants may be airborne as vapour, droplets or dust particles, and in the soil in aqueous or particulate forms. In the case of aqueous systems, they can exist as emulsions, as dissolved ions or molecules and as suspended or sedimentary particles. Environmental particles have been reviewed in the first two volumes of this series [1,2]. 

Cells R, Cox L, Hermosin MC, Cornejo J (1996) Retention of metamitron by model and natural particulate matter. Intern J Environ Anal Chem 65 245-260 Chaney RL (1989) Toxic element accumulation in soils and crops protecting soil fertility and agricultural food chains. In Bar Yosef B, Barrow NJ, Goldschmid J (eds) Inorganic contaminants in the vadose zone Springer, Heidelberg, pp 140-159 Charlatchka R, Cambier P (2000) Influence of reducing conditions on solubility of trace metals in contaminated soils. Water, Air Soil PoUut 118 143-167 Chien SH, Clyton WR (1980) Application of Elovich equation to the kinetics of phosphate release and sorption in soils. Soil Sci Am J 44 265-268... 

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