Extraction of contaminated soil

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). 

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. 

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 aim of this work is the development of pyrene determination in gasoline and contaminated soils. For this purpose we used room temperature phosphorescence (RTP) in micellar solutions of sodium dodecylsulphate (SDS). For pyrene extraction from contaminated soils hexane was used. Then exttacts earned in glass and dried. After that remains was dissolved in SDS solution in the presence of sodium sulphite as deoxygenation agent and thallium (I) nitrate as heavy atom . For pyrene RTP excitation 337 nm wavelength was used. To check the accuracy of the procedures proposed for pyrene determining by RTP, the pyrene concentrations in the same gasoline samples were also measured by GC-MS. 

The Brio refining site is approximately 58 acres in size and is the location of a former chemical production, recovery, refinery, and regeneration facility. The site includes closed impoundments into which hazardous substances were disposed in bulk, storage tanks, and approximately 1,750 drums of hazardous substances. Remediation activities included the excavation and incineration of contaminated soil, installation of protective liners around selected pits, and the installation of a groundwater extraction system adjacent to a gully. 

Economic feasibility studies suggest that even at the present state of the art photocatalytic technology indeed can be competitive with the traditional carbon adsorption or incineration technologies in treatment of contaminated soil vapor extraction vents and small scale VOC-containing vents [28]. Rapid progress in basic and applied research in photocatalysis suggests... 

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

Solvent extraction uses an organic solvent to extract toxic substances from contaminated liquid or solid.67 Examples can be found in the section dealing with the treatment of contaminated soil. 

Soil vacuum extraction is cost-effective if the volume of contaminated soil exceeds 382 m3 (500 yd3), and if the contaminated area is more than 6 m (20 ft) deep otherwise, soil excavation and... 

Manganese oxides have been used to remediate contaminated soils as well. Hydrous manganese oxides decreased Cd and Pb in rye grass (Lolium spp.) and tobacco (Nicotiana tabacum L.) from soils with pH 7.4-7.8 (Mench et al., 1994). Cadmium concentrations decreased in water and in 0.1 M Ca(N03)2 and acetic acid extracts of treated soils (Mench et al., 1994). 

Chaignon, V., SanchezNeira, I., Herrmann, P., Jadlard, B. and Hinsinger, P. (2003). Copper bioavailability and extractability as related to chemical properties of contaminated soils from a vine-growing area , Environmental Pollution, 123, 229-238. 

The preliminary study identified approximately 2300 yd3 of contaminated soil with a hot zone of approximately 800 yd3, which required the bulk of remediation effort. A pilot air sparge/soil vapor extraction study was made to define remediation costs. The remediation effort was estimated to extend for 3 years. 

According to the vendor, MITUs can be half the cost of alternative technologies such as incineration, landfilling, or soil vapor extraction (SVE) (D17269U, p. 8). At a petroleum and gas distribution site in Schuylkill Haven, Pennsylvania, 4200 tons of contaminated soil were treated at a cost of 18.63/ton. (D17269U, p. 30). Additional vendor-supplied cost information is presented in Table 1. 

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. 

The technology uses continuous flushing of contaminated soil with water from the aquifer that has been extracted and treated. Treated, nutrient- and oxygen-enhanced aquifer extract is recirculated to leach additional contaminants from the soil and the groundwater plume. Recirculation ensures steady biological reduction of contaminants. The Express process technology is currently commercially available from WaterSmart Environmental, Inc. All information contained herein has been provided by the vendor. 

Contamination in low-permeability soil is a problem of major importance in environmental remediation. Traditional treatments of contaminated soils include bioremediation methods, vapor extraction, and what are known as pump-and-treat methods. However, poor accessibility to the contaminants and difficulties in delivering reagents used for treatment make these current in situ methods very ineffective. Electroosmosis (combined possibly with one or more of the traditional techniques) can potentially serve as an alternative in situ treatment process, as shown in Figure 12.14. 

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. 

It is not always necessary or required to digest the entire sample in order to free the metals for analysis. In some cases it is not even desirable. In studies of contaminated soils, for instance, the analyte of interest may be present as a soluble salt from a pollution source, as well as also being present in the structure of the mineral crystals. The soluble form is of concern, as it is available to biota and may eventually contaminate groundwater. That in the insoluble particles is not of interest. In such cases, where the analyte is much more soluble than the matrix or where the metals included in the matrix are not of interest, an extraction process rather than complete solubilization is preferred. This is treated further in Section 5.10. 

Energetic materials like TNT or other nitroaromatic compounds are readily soluble in liquid and supercritical carbon dioxide (SC-CO2). Extraction processes using SC-CO2 as an extracting solvent (supercritical fluid extraction SFE) permit the discharging of TNT and its breakdown products out of contaminated soils or other matrices [1],... 

The on-line detection of TNT and some of its breakdown products during their SC-CO2 extraction out of contaminated soils was simulated under different pressures and temperatures. The nitroaromatic compounds dissolved in sc-C02 were identified by their characteristic UV-VIS absorption bands. A quantification of the analytes was possible for concentrations lower than 1 ppm. 

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. 

T. R. Reilly, The Cleanup of Contaminated Soils and Sludges by a Solvent Extraction Process A Case Study , M.S. Thesis, Department of Chemical Engineering, Princeton University (1985). 

Figure 4 shows the results of the extraction of water (figure 4a) and dry and wetted soil (figure 4b and 4c, respectively) using pure carbon dioxide, carbon dioxide with 2 mol % benzene, and carbon dioxide with 2 mol % methanol at 15 MPa and 298 K. For the extraction of dry contaminated soil, the distribution coefficient of phenol between the soil and pure carbon dioxide was 0.35, as shown in Figure 4b. The presence of benzene increased the distribution coefficient almost 100 %, while the presence of methanol resulted in the removal of essentially all of the phenol from the soil (within experimental accuracy, K-values > 7 correspond to almost complete removal). For the extraction of wetted soil (10 wt.% water )with pure carbon dioxide the distribution coefficient of phenol was again 0.35. The effect of the entrainers on this system, however.

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