Extraction of contaminants

Although the process requires the addition of a phosphate donor, such as glycerol-2-phosphate, it may be a valuable tool for cleaning water contaminated with radionuchdes. An alternative mode of uranium precipitation is driven by sulfate-reducing bacteria such as Desulfovibrio desulfuricans which reduce U(VI) to insoluble U(IV). When combined with bicarbonate extraction of contaminated soil, this may provide an effective treatment for removing uranium from contaminated soil (85). 

Extraction of contaminants from the soil and accumulation in the plant tissue for removal (phytoextraction)... 

Groundwater extraction Ex situ hydrogen peroxide, or permanganate into die subsurface to oxidize contaminants Extraction of contaminated... 

In both cases, the samples from contaminated sites were rinsed with a solvent to obtain an extract of contaminated transformer oil. The effects of biological degradation were investigated by using a commercial mixture of microorganisms and pure strain under aerobic and anaerobic condition. In the thermal method, a laboratory plasma system was used to decompose the contaminated transformer oil by a direct injection of the oil extract into the plasma system or by melting the extract samples with power plant fly ash in the plasma reactor. For the contaminated transformer oil both methods showed a destruction efficiency of 99.99% and the products of destruction were environmentally friendly. 

Invertebrates. In a sediment exposure experiment using invertebrates, for extraction of contaminants (including NP), invertebrates... 

Cosolvent flooding is accomplished by the introduction of a cosolvent solution, with subsequent extraction of contaminated groundwater and NAPL. In one reported field test study that focused on enhanced dissolution, the use of about nine pore volumes of a 70% ethanol, 12% pentanol solution injected into a test cell resulted in about 81% bulk NAPL removal, with a higher removal efficiency for several other individual compounds. In another field test study, where mobilization removal was emphasized, injection of about four pore volumes of a mixture of tert-butanol and w-hcxanol into a test cell resulted in the removal of about 80% of the bulk NAPL, and higher removal efficiency of the more-soluble NAPL compounds. 

Soxhlet, sonication, supercritical fluid, subcritical or accelerated solvent, and purge-and-trap extraction have been introduced into a variety of methods for the extraction of contaminated soil. Headspace is recommended as a screening method. Shaking/vortexing is adequate for the extraction of petroleum hydrocarbons in most environmental samples. For these extraction methods, the ability to extract petroleum hydrocarbons from soil and water samples depends on the solvent and the sample matrix. Surrogates (compounds of known identity and quantity) are frequently added to monitor extraction efficiency. Environmental laboratories also generally perform matrix spikes (addition of target analytes) to determine if the soil or water matrix retains analytes. 

Filtration studies are conducted to investigate the filtration process (e.g., the binding of the analytes of interest to the applied filtration device, filtration discard volume, and the extraction of contaminants). 

Promotes better extraction of contaminants from or delivery of materials to the subsurface. 

The Lockheed Corporation, now Lockheed Martin, has designed, constructed, and operated batch and continuous ex situ treatment facilities for acid extraction of contaminants. This technology involves the solubilization of contaminants, followed by the isolation of soluble elements into appropriate forms. The goal of this technology is to minimize the volume of hazardous and radioactive constituents for disposal. Physical separation techniques may be used as pretreatment steps. 

TERRA-PURE is an in situ technology that ntihzes a flushing system for extraction of contaminants from soil. According to the vendor, it is applicable to organic and inorganic contaminants present at relatively high concentrations and to non-aqueous-phase liquids. 

Environmental treatments for removing pollutants include in situ degradation with microorganisms and enzymes, use of biofilters, and extraction and sorption of the pollutants. These and other techniques will be covered in this chapter, but for various reasons, the extraction of contaminants is of particular interest primarily because extraction requires no particular pretreatment of the chemical. Air can be injected into the soil around an aquifer and recovered in sorption towers for concentration and removal from the environment. 

Jacobs, M.W., Delfmo, J.J. and Bitton, G. (1992) The toxicity of sulfur to Microtox from acetonitrile extracts of contaminated sediments, Environmental Toxicology and Chemistry 11 (8), 1137-1143. 

Majority MAE applications have been in the extraction of PAHs, PCBs, pesticides, phenols, and total petroleum hydrocarbons (TPHs) from environmental samples. MAE has also been used in the extraction of contaminants and nutrients from foodstuffs, active gradients from pharmaceutical products, and organic additives from polymer/plastics. Table 3.14 lists some typical applications. Readers interested in the details of MAE applications can find more information in some recent reviews [85-87],... 

Previous reproductive toxicology studies in laboratory animals examining the effects of prenatal exposure to fumonisin demonstrated a potential risk to the developing fetus. Studies using an aqueous extract of contaminated maize-culture material of F. verticillioides reported that fumonisin was developmentally toxic in hamsters (Floss et al., 1994 Penner et al., 1998). In addition, purified fumonisin Bi was shown experimentally to cause fetal toxicity in rats and mice (Collins et al., 1998 Reddy et al., 1996). In another study, pregnant CD1 mice treated with a semipurified extract... 

Continuous Extraction of Contaminated Soil with Supercritical Water... 

A new apparatus was built for continuous extraction of contaminated soil with supercritical water (Tc = 647 K, pc = 22.1 MPa). Extraction times could be reduced to 28 s at operating conditions of 663 K and 24 MPa (0.5 wt% soil in water). 

A new apparatus was developed for continuous extraction of contaminated soil material for high pressure (25 MPa) and high temperature (663 K) operating conditions. The extraction of hydrocarbon contaminants from long weathered and highly contaminated soil material could be realised with supercritical water under parallel flow. Within a residence time of only 28 s suspensions of less than 0.75 wt% soil in water could be cleaned (> 90 %). For a concentration of 1 wt% soil in water 43 s were needed to achieve a clean-up result of 98.3 %. The continuous extraction process can be carried out multistage. Then higher concentrated suspensions (2-4 wt%) can be also cleaned by supercritical water extraction. 

The major problems encountered with these techniques are co-extraction of contaminants from the... 

Anitescu, G., Tavlarides, L.L. Supercritical extraction of contaminants from soil and sediments. J. Supercrit. Fluids 38, 167-180 (2006)... 

Apart from obvious dry cleaning applications, potential applications of C02-based microemulsions include (i) printed circuit board cleaning, (ii) extraction of contaminants from soils, (Hi) cleaning of polymers, foams, aerogels, porous ceramics, and laser optics, (iv) regeneration of activated carbon beds or catalysts, and (v) the separation of dyestuffs from textiles. 

There are a number of recent papers that deal with the application of disks to the extraction of contaminated waters. For example, Chiron and co-workers... 

Dierkes, F., Haegel, F.-H. and Schwuger, M.J. (1998) Low-temperature microemulsions forthe in situ extraction of contaminants from soil. Colloids Surf. A, 141(2), 217-225. 

Shapiro AP, Renaud PC and Probstein RE (1989) In-situ extraction of contaminants from hazardous waste sites by dectroosmosis. In Mura-lidhara HS, ed. Solid/Iiquid separation waste management and productivity enhancement, pp. 346-353. Batelle Press, Columbus/Ohio. 

---