Solvent Contaminants

Analytical Supercritical Fluid Extraction and Chromatography Supercritical fluids, especially CO9, are used widely to extrac t a wide variety of solid and hquid matrices to obtain samples for analysis. Benefits compared with conventional Soxhlet extraction include minimization of solvent waste, faster extraction, tunabihty of solvent strength, and simple solvent removal with minimal solvent contamination in the sample. Compared with high-performance liquid chromatography, the number of theoretical stages is higher in... 

Metaltec is the 16-acre site of a small metal casing fabrication plant and includes an unlined lagoon used for dumping waste solvents from the plant s operations. The waste solvents contaminated both the soil and groundwater on site and were the focus of the remediation efforts. Four parcels of land on the site were originally identified for remedial action. Soil remediation was completed on three of the four parcels in prior... 

Solvents Solvent contamination is a special form of foreign fluid contamination in which the original contaminating substance is a chlorinated solvent. Chlorinated solvents or their residues may, when introduced into a hydraulic system, react with any water present to form highly corrosive acids. 

Polychloroprene and acrylonitrile-butadiene rubber compounds have satisfactory chemical resistance but, except for phosphoric acid, are not suitable for mineral acids at higher concentrations. However, they have good resistance to oils, acrylonitrile-butadiene rubber being the better, and so are often used in oil-contaminated aqueous environments. Generally, abrasion resistance is only fair. Normal maximum working temperature is about 100°C. Acrylonitrile-butadiene rubber ebonites are sometimes used especially where solvent contamination occurs, but are normally very brittle and so should be used with care. 

Respiratory Effects. One study suggested increased respiratory disorders (asthma, bronchitis, pneumonia) in children with chronic exposure to a solvent-contaminated water supply (Byers et al. 1988). Two municipal wells in eastern Woburn, Massachusetts, were found to contain several solvents including trichloroethylene (267 ppb) and tetrachloroethylene (21 ppb). The increased susceptibility to infection may be secondary to effects on the immune system. Accurate chemical-specific exposure levels for individuals could not be determined because the water distribution system was designed to use water from different wells at different rates and times. Other limitations of this study are described in Section 2.2.2.8. 

Byers VS, Levin AS, Ozonoff DM, et al. 1988. Association between clinical symptoms and lymphocyte abnormalities in a population with chronic domestic exposure to industrial solvent-contaminated domestic water supply and a high incidence of leukemia. Cancer Immunol Immunother 27 77-81. 

Dojka MA, P Hugenholtz, SK Haack, NR Pace (1998) Microbial diversity in a hydrocarbon- and chlorinated-solvent-contaminated aquifer undergoing intrinsic bioremediation. Appl Environ Microbiol 64 3869-3877. 

Advantages Low cost No grinding Broad applicability High b.p. solvent contamination of analyte Low investment Simple equipment Simultaneous extractions in series Low investment Simple equipment Rapid Economic solvent use Good reproducibility Low investment Simple equipment Economical Simple equipment Not traumatic Almost solvent free Concentrated analyte Rapid Low temperatures Rapid Automated Simultaneous extraction Low solvent use Rapid User friendly Automated Sequential extractions Not analyst labour intensive... 

A solvent contaminated with 0.03 kmol/m3 of a fatty acid is to be purified by passing it through a fixed bed of activated carbon which adsorbs the acid but not the solvent. If the operation is essentially isothermal and equilibrium is maintained between the liquid and the solid, calculate the length of a bed of 0.15 m in diameter which will allow operation for one hour when the fluid is fed at 1 x 10-4 m3/s. The bed is free of adsorbate initially and the intergranular voidage is 0.4. Use an equilibrium, fixed-bed theory to obtain the length for three types of isotherm ... 

An example of a supercritical C02 extraction is given in Procedure 12.3. Note that methanol is added as a modifier and that extraction is rapid, taking only 15 minutes. Supercritical extractions are used when the analyte is difficult to extract, as when it is strongly associated with soil solid, and when it is particularly desirable to have an extract free of solvent contamination that might interfere with subsequent analysis. 

Leeson, A. and Alleman, B. C. (editors), 1999, Engineered Approaches for In Situ Bioremediation of Chlorinated Solvent Contamination. Battelle Press, Columbus, OH, Vol. 5, No. 2, 336 pp. 

Hazaga, D., Fields, S., and Clemens, G. R, 1984, Thermal Treatment of Solvent Contaminated Soils In Proceedings of the USEPA Fifth National Conference on Management of Uncontrolled Hazardous Waste Sites, Washington, D.C., pp. 404-406. 

Grindstaff, M., 1998, Bioremediation of chlorinated solvent contaminated groundwater. Prepared for US EPA Technology Innovation Office. 

EPS is also conducting trials on textile dye wastewater using a mobile pilot plant that will also be used to treat solvent-contaminated wastewater at an automotive facility. 

The potential advantages of using derivatized and immobihzed solvents include reduced VOC emissions, negligible global warming potential, no ozone depleting potential, cleaner and easier separations from water, and reduced solvent contamination in aqueous waste streams. 

Clearly, the most effective way to avoid problems with solvent contamination of the environment is to eliminate the use of the solvent entirely. Even though this clearly is not possible for most applications, there are some innovative solvent-free cleaning processes that deserve mention. 

Solvent extraction nonpolar, volatile, semivolatile ambient temperature, large volumes, low salt concentration solvent contamination, specificity, concentrate storage 18-21... 

Continuous liquid-liquid extractors (CLLEs) using a small amount of solvent that is continuously recycled would be more effective for this type of sampling. A CLLE system would be less affected by solvent contaminants, and less solvent would be needed. 

The biodegradation of trichloroethylene is the most studied since this is probably the most widespread halogenated solvent contaminant. Several substrates drive ttichlorethylene co-oxidation, including methane, propane, propylene, toluene, isopropylbenzene, and ammonia (25). The enzymes that metabolize these substrates have subtly different selectivities with regard to the halogenated solvents, and to date none are capable of co-oxidizing carbon tetrachloride or tetrachloroethylene. Complete mineralization of these compounds can, however, be achieved by sequential anaerobic and aerobic process. Biorem edia tion. 

The methyl ethyl acetic acid may also be obtained by extraction of the acidified solution with ether. This method is not recommended, as small amounts of alcohol which are invariably present in this solvent, contaminate the product by the formation of the ethyl ester. 

Formaldehyde, along with other short-chain aldehydes such as acetaldehyde, is a low molecular weight, volatile, reactive contaminant that can be present at low levels from a variety of sources (e.g., excipients such as polyethylene oxide, polyethylene glycol (64,65), or from carbohydrate degradation (66), solvent contamination (51), packaging materials (52), etc.). Formaldehyde is known to react with amines (Fig. 33) to form a reactive N-hydroxymethyl compound (a hemiaminal) that can further react with other nucleophiles. Reaction of formaldehyde with amino acids (67) can cause... 

Besides the fire hazard that they present, any solvent that is spilled on clothing or the skin presents a health problem. Suitable impervious gloves and eye protection must be worn when using any solvent. Contaminated clothing must be removed and the contact area washed well. As the solvents will remove the natural oils from the skin, they must be replaced by an industrial grade of barrier cream. 

Water/Solvents. Are the levels of water or solvent contaminants important, requiring a tight specification If so, what levels should be set and what process (e.g., drying conditions) is needed to meet the specification ... 

Figure 16.35 (part I) shows how palladium(II) acetate, triphenylphosphane and water react to furnish the complex F as the active palladium(O) catalyst. For a long time, the presence of water had not been suspected as a solvent contaminant. It was unknown that it is essential for initiating the reaction process. In the mid-1990s, Amatore and Jutand demonstrated that the reduction Pd(II) —> Pd(0), which is involved in the formation of F, is effected by a tri-... 

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