Environmental chemical separation

Wegeng mentions the use of micro reactors for the cleanup of environmental contamination [1]. In particular, he refers to downwell groundwater cleanup by micro-chemical separations and conversions such as destruction of organics. 

Environmental chemical releases due to human activities may be accidental (usually acute) or as an attendant consequence of some planned activity (usually chronic). Traditionally, spills have been separated from steady discharges because of statutory distinctions, but any integrated pollutant assessment must... 

The environmental fate of a chemical is usually a function of many physical and chemical processes which the chemical may encounter from the time it is applied until it dissipates. Such processes include Photolysis on surfaces, in solution or in air, hydrolysis, biolysis, oxidation, transport by drift, erosion (runoff) and other means of transport and dissipation. Historically, most risk assessments have emphasized the toxicity of a chemical separately without adequate consideration of the amount of exposure to a chemical which an organism might... 

The plutonium concentration in marine samples is principally due to environmental pollution caused by fallout from nuclear explosions and is generally at very low levels [75]. Environmental samples also contain microtraces of natural a emitters (uranium, thorium, and their decay products) which complicate the plutonium determinations [76]. Methods for the determination of plutonium in marine samples must therefore be very sensitive and selective. The methods reported for the chemical separation of plutonium are based on ion exchange resins [76-80] or liquid-liquid extraction with tertiary amines [81], organophosphorus compounds [82,83], and ketones [84,85]. 

As liquid chromatography plays a dominant role in chemical separations, advancements in the field of LC-NMR and the availability of commercial LC-NMR instrumentation in several formats has contributed to the widespread acceptance of hyphenated NMR techniques. The different methods for sampling and data acquisition, as well as selected applications will be discussed in this section. LC-NMR has found a wide range of applications including structure elucidation of natural products, studies of drug metabolism, transformation of environmental contaminants, structure determination of pharmaceutical impurities, and analysis of biofiuids such as urine and blood plasma. Readers interested in an in-depth treatment of this topic are referred to the recent book on this subject [25]. 

The radiometric method is used to determine Tc in environmental water samples . The work provides a carrier-free procedure for the determination of Tc in aqueous solutions as low as 0.5 dpm/1. The chemical separation is followed by electrodeposition on a stainless-steel cathode involving determination of Tc by counting. 

An isotope dilution mass spectrometric method involves the addition of a known quantity of Tc followed by chemical separation, purification, and measurement of the Tc/ Tc isotopic ratio . An improved technique has been developed for the analysis of Tc in environmental samples. After spiking with Tc the isolated technetium is concentrated onto anion exchange beads. Determination of as little as 1 pg has been achieved through the enhanced ionization efficiency afforded by the resin bead source ... 

Under the sponsorship of the National Science Foundation and in collaboration with scientists in New Zealand, Burnett of Florida State University is attempting to develop a chemical separation technique for uranium, thorium, and their daughter products (Federal Research in Progress 1990). Other than this research, no studies are in progress for improving the method for the quantification of thorium and daughter products in biological and environmental samples. 

The Snrbec-ART Environmental, L.L.C. (Snrbec), soil washing technology is a process based on mining and mineral processing principles that incorporates physical and chemical separation techniqnes (D12463A, p. 3). The technology separates and treats oversized fractions and sand fractions so that they can be placed back on the site as clean backfill. Contaminants are concentrated in the fines, and this fraction can be managed separately for further treatment or disposal. 

Noble, R.D., Terry, P.A., Principles of Chemical Separations with Environmental Applications, Cambridge University Press, UK (2004)... 

Conventional radiochemical methods for the determination of long-lived radionuclides at low concentration levels require a careful chemical separation of the analyte, e.g., by liquid-liquid, solid phase extraction or ion chromatography. The chemical separation of the interferents from the long-lived radionuclide at the ultratrace level and its enrichment in order to achieve low detection limits is often very time consuming. Inorganic mass spectrometry is especially advantageous in comparison to radioanalytical techniques for the characterization of radionuclides with long half-lives (> 104 a) at the ultratrace level and very low radioactive environmental or waste samples. 

Much of the effort on environmental chemicals that contaminate food has concentrated on a small range of chlorinated chemicals. In addition to the chlorinated PCDDs, PCDFs and PCBs already mentioned, other chlorinated compounds can be separated into two groups chlorinated aromatic compounds and chlorinated aliphatic compounds. Although there is a number of organochlorine pesticides that are persistent in the environment, these will not be considered here, as they comprise an extensive field of study in their own right. 

McLeod, K.W., Adriano, D.C., Boni, A.L., Corey, J.C., Horton, J.H., Paine, D. Pinder, J.E. Ill (1980) Influence of a nuclear fuel chemical separations facility on the plutonium content of a wheat crop. Journal of Environmental Quality, 9,306-15. 

Noble and Terry, Principles of Chemical Separations with Environmental Applications Orbey and Sandler, Modeling Vapor-Liquid Equilibria Cubic Equations of State and their Mixing Rules... 

Other Chromatographic and Related Techniques. Supercritical fluid chromatography (SFC), capillary electrophoresis (CE), and several related separation techniques are occasionally used in environmental chemical determinations. The CE technique is very... 

Actinides found as environmental contamination in mosses collected from a bog in the eastern Italian Alps were analyzed after their chemical separation by extraction chromatography (deposited on steel targets) with respect to isotope ratios and their concentration was determined by LA-ICP-MS. Moss samples were contaminated with a variety of actinide isotopes. The detection limits for actinides were determined as 3.6-7.2 x 10 gg for " Am and respectively. The Pu/ Pu isotope ratio (0.212 0.003) was almost constant within experimental error for all samples investigated. Pu contamination in moss samples was mainly the result of global fallout after nuclear weapons tests. " Am was found at the 2x 10 " gg level. This example demonstrates that mosses can be used as bioindicators for environmental contamination. ... 

Due to their peculiar solvent properties, supercritical fluids offer a range of unusual chemical possibilities such as in environmentally benign separation and destruction of hazardous waste, as well as for new materials synthesisd" These intriguing reaction media make it possible to sensitively control reaction rate and selectivity with changes in temperature and pressure. The thermophysical properties of water as well as more than 70 other fluid systems have been formulated and/or compiled by lAPWS and NIST. ... 

Although the attainable accuracy is limited to around a few percent in this simple 4jr p-counting method, this method can be applied to the measurements of weak source, and hence can play a special role in the environmental radioactivity measurements after chemical separation. 

It can be concluded that there is a potential for membrane separation of almost any gas from a mixture of gases if physical and chemical properties are carefully considered as well as material properties and durability, possible transport mechanisms, and optimum process conditions evaluated. Creative reflection and advanced research will be able to develop this environmental friendly separation technique for applications within many areas in the future, and hopefully be able to displace old, energyconsuming (and not so clean) technology or combine with them in hybrid process solutions. The costs of the final solution will always be a major issue for commercialization. 

Most chemical classes have been separated and analyzed by CEC [6]. These include many classes of pharmaceuticals, environmental chemicals, explosives, natural products, drugs of abuse, polypeptides, oligosaccharides, nucleosides, and their bases and polynucleotides. Applications of CEC are readily found in Analytical Abstracts for example, a publication of the American Chemical Society, or the indexes of journals such as the Journal of Chromatography. 

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