Sources, Production, and Uses

Lanthanides are constituents of many different minerals in igneous rocks, shale, and silicates however, the two major sources for commercial production are bastnasite (a flu-orocarbonate) and monazite (a phosphate) 

These two minerals, which may be digested with H2SO4 or NaOH, contain most of the lanthanides in various concentrations, including (on a percentage basis) La (25) Sm (3) Yb, Ho, and Tb (0.03-0.05) and Lu and Tm (0.003-0.01). Promethium is a man-made element and has not yet been found in the Earths crust. 

Lanthanides have been refined, isolated, and separated using techniques such as ion-exchange and solvent (liquid-liquid) extraction, and electrochemical deposition. Recently, a technique was developed for separating rare earths employing selective reduction and fractional distillation (Hedrick 2000). An advantage of the new process is that it achieves separations two orders of magnitude greater than liquid-liquid extraction however, the process is 

The uses of lanthanide compounds are diverse and are expanding due to modern technological advances. In 2000, the principal applications for the rare earths were glass polishing and ceramics, 39% automotive catalytic converters, 22% permanent magnets, 16% petroleum refining catalysts, 

The high thermal neutron absorption cross-sections and high melting points of various lanthanides (Sm, Eu, Dy, Gd) are two properties that make them ideal for use in nuclear reactor control rod applications. Cerium dioxide has been developed into a sunscreen that has higher transparency and higher ultraviolet blocking proper- 

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Brautlecht CA. Starch Its Sources, Productions and Uses. New York, NY Reinhold 1953. 

Sources, Production and Uses, Waste Products, and Recycling... 

It is very difficult to evaluate the overall environmental impact of one fibre over another some information is very difficult to access or applies only to a specific region and judgments have to be made on how to weigh the different impaets of the source, production and use of the product. 

In the biotechnology age, the body really does have cash value as a potential source of valuable patents, marketable products and useful... 

Because acrylonitrile is readily volatile, significant releases to air may occur during acrylonitrile production and use (Hughes and Horn 1977 Miller and Villaume 1978). Kayser et al. (1982) estimated that 11,790 kkg/yr (metric tons per year) of acrylonitrile was released from these sources, accounting for 87% of all acrylonitrile released to the... 

It has been estimated that over 100,000 workers are potentially exposed to acrylonitrile during production and use (NIOSH 1977, 1988). Occupational exposures include plastic and polymer manufacturers, polymer molders, polymer combustion workers, furniture makers, and manufacturers of fibers and synthetic rubber (EPA 1980a). Other populations who could have elevated exposure to acrylonitrile are residents in the vicinity of industrial sources or chemical waste sites. 

The major sources of hexachloroethane releases to air are from its production and use in the organic chemical industry. As shown in Table 5-1, an estimated total of 49,716 pounds of hexachloroethane, amounting to about 97% of the total industrial environmental release, was discharged to the air from manufacturing and processing facilities in the United States in 1993 (TRI93 1995). The TRI data should be used with caution since only certain types of facilities are required to report. This is not an exhaustive list. 

Primary sources of environmental contamination with PCDD/PCDFs in the past were the production and use of organic chemicals containing chlorine. PCDFs were formed as inadvertent by-products in the production and use of PCBs and, in combination with PCDDs, in such high-temperature processes as waste incineration, the metal industry, home heating and other energy production processes. 

Hb and Ni-reconstituted Hb were prepared according to reported methods (13). Mb was made by the method of Alston and Storm (14) Solutions of the proteins in 0.05 M phosphate buffer at pH 7.5 were used for obtaining spectra. The proteins are stable in air and do not photodecompose. Ni protoporphyrin IX (Ni(ProtoP)), Ni uroporphyrin I (Ni(UroP)), and Ni octaethylporphyrin (Ni(OEP)) were obtained from Porphyrin Products and used without further purification. All solvents were of highest purity obtainable from commercial sources. All materials showed the literature uv-visible absorption spectra. Absorption spectra were obtained on a Perkin-Elmer Model 330 spectrophotometer. 

Exposure data and other information on an agent under consideration are also reviewed. In the sections on chemical and physical properties, on analysis, on production and use and on occurrence, published and unpublished sources of information may be considered. 

The world energy crisis of the 1970s, however, spurred interest once again in ethanol as a transportation fuel source. Brazil adopted the widespread production and use of Alcool, hydrated ethanol, and Gasolina a 78 22 ratio blend of gasoline ethanol as a motor fuel. Other countries developed policies to maintain a fuel grade ethanol industry by conversion of biomass. Also, clean air and reformulated fuel policies have helped to promote the use of ethanol as a viable alternative fuel. 

Occupational exposure to ethylbenzene may occur by inhalation during its production and use. Most occupational exposures are related to technical grades of mixed xylenes used as solvents in various paints and coatings, inks, insecticides and in rubber and plastic production, as well as from the production and handling of gasoline and bitumen. Ethylbenzene from these sources as well as from vehicle emissions is ubiquitous at Xg/m levels in ambient air. It is a component of tobacco... 

Thousands of tonnes of methyl chloride are produced naturally every day, primarily in the oceans. Other significant natural sources include forest and brush fires and volcanoes. Although the atmospheric budget of methyl chloride can be accounted for by volatilization from the oceanic reservoir, its production and use in the manufacture of silicones and other chemicals and as a solvent and propellant can make a significant impact on the local atmospheric concentration of methyl chloride. It has been detected at low levels in drinking-water, groundwater, surface water, seawater, effluents, sediments, in the atmosphere, in fish samples and in human milk samples (Holbrook, 1993 United States National Library of Medicine, 1998). Tobacco smoke contains methyl chloride (lARC, 1986). 

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