Contaminated chemical extraction

Contamination. Manufacturers of cosmetics must be careful to guard against chemical and microbial contamination. Chemical contamination, which may result from the presence of undesirable impurities in raw materials, is avoidable by adhering to rigid specifications for raw materials. Compendial specifications and pubHcations by the CTFA and other professional societies form the basis of most intracompany raw material specifications. Moreover, all packaging components must meet not only physical and design specifications but also such chemical requirements as extractables and absence of dust and similar contaminants (see Packaging, cosLffiTics and pharmaceuticals). 

Ma L.Q., Rao G.N. Effects of phosphate rock on sequential chemical extraction of lead in contaminated soils. J Environ Qual 1997b 26 788-794. 

Therefore, for infrared spectroscopic methods, the total petroleum hydrocarbons comprise any chemicals extracted by a solvent that are not removed by silica gel and can be detected by infrared spectroscopy at a specified wavelength. The primary advantage of the infrared-based methods is that they are simple and rapid. Detection limits (e.g., for EPA 418.1) are approximately 1 mg/L in water and 10 mg/kg in soil. However, the infrared method(s) often suffer from poor accuracy and precision, especially for heterogeneous soil samples. Also, the infrared methods give no information on the type of fuel present in the sample, and there is little, often no information about the presence or absence of toxic molecules, and no specific information about potential risk associated with the contamination. 

OSHA Toxicologic Review of Selected Chemicals Methylene Bis-(4-Hexylisocyanate). OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq http //wTvw.cdc.gov/niosh/ pel88/5124-30.html... 

Speciation science seeks to characterise the various forms in which PTMs occur or, at least, the main metal pools present in soil. This chapter provides a review of the single and sequential chemical extraction procedures that have been more widely applied to determine the plant and the human bioavailability of PTMs from contaminated soil and their presumed geochemical forms. Examples of complementary use of chemical and instrumental techniques and applications of PTMs speciation for risk and remediation assessment are illustrated. 

This chapter provides a review of the single and sequential chemical extraction procedures that have been more widely applied to estimate the plant and the human bioavailability of PTMs from contaminated soil and their presumed geochemical forms. 

Kirpichtchikova, T. A., Manceau, A., Spadini, L., Panfili, F., Marcus, M. A., andjacquet, T. (2006). Speciation and solubility of heavy metals in contaminated soil using X-ray microfluorescence, EXAFS spectroscopy, chemical extraction, and thermodynamic modeling. Geochim. Cosmochim. Acta 70, 2163-2190. 

Table 7.1 Chemical contaminants of extractive industry wastewaters...

Heron G., Crouzet C., Bourg A. C. M., and Christensen T. H. (1994b) Speciation of Fe(II) and Fe(III) in contaminated aquifer sediments using chemical extraction techniques. Environ. Sci. Technol. 28, 1698—1705. 

Phytoavailability of a metal ion varies with the particular metal, soil properties, and plant species. It is difficult to assess the value of the large number of studies that have reported metal extractants and plant availability of metals on different soils with or without the application of contaminants such as sewage sludges. Comparisons between studies can be virtually impossible because the duration of treatments prior to extraction of the metals was often widely different. Moreover, few studies report metal availability tests, determined using chemical extractions, for native species under real field conditions (e.g., Gough et al., 1980 Krishnamurti et al., 1995a). 

The degree of bioavailability of organic compounds depends critically on their chemical structure which determines the kinds of interaction that may take place within the solid phase. For example, linear alkylbenzenesulfonates are readily desorbed from sediments, so that their biodegradability and potential toxicity is largely unaffected by the presence of sediments (Hand and Williams 1987). On the other hand, benzo[a]pyrene even though accessible to chemical extraction appears to be available to biota only to a limited extent (Varanasi et al. 1985). This is consistent with the view noted earlier that chemical extractability is not a useful measure of bioavailability for naturally aged samples as opposed to those which have been spiked with the contaminant (Kelsey et al. 1997). 

Clean particles are dewatered, separated into heavy and light materials, and returned to the site. Contaminated particles undergo a final series of washing, separation, and chemical extraction processes to remove any remaining clean particles. Finally, the contaminated material is clarified and concentrated before being disposed of or treated. 

As mentioned above, it is an obligation of the filter user to validate the sterilization processes applied to the niter. Most often sterilizing filters will be autoclaved. The effects of a particular autoclave process on the quality and quantity of extractables obtained from filters should be evaluated using the pharmaceutical fluid that is intended to be filtered. The filtrate should be demonstrated to be particle free and biologically inert chemical extractables should not exceed the levels of contaminants allowed in the product quality specification. 

Removal the contaminated soil is exposed to chemical extraction and/or thermal treatment with volatile elements or compounds, and to other leaching or immobilizing processes. It is a high-cost procedure. 

---