Cr VI Removal from groundwater by means of nanoscopic Fe particles supported on MgO granules

In situ soil flushing should be considered for applications involving petroleum hydrocarbons, chlorinated hydrocarbons, metals, salts pesticides, herbicides, and radionuclides. Current interest seems to be focusing on the use of in situ flushing for chlorinated hydrocarbons. A unique capability centers on cleaning up contaminated soil beneath the structures. Many industrial sites throughout the U.S. have chlorinated hydrocarbons in the subsurface. Since the excavation and other existing remediation strategies require access, in situ soil flushing offers clear advantages.
Other advantages include: no soil replacement and/or disposal costs, no disruption of the ecosystem, cost advantages at greater depths, and minimized worker exposure to contaminants. Excavation can also be cost prohibitive in complex hydrogeologic environments.
In general, soil flushing is most effective in homogeneous permeable soils with low recharge capacity for metals and low adaptive capacity for inorganic contaminants.
Soil flushing may also be appropriate for the following applications:
• Recovery of mobile degradation products formed after soil treatment with chemical oxidizing agents. This application may be particulary appropriate if excavation presents a high safety and health hazard;
• Enhancement of oil recovery operations. Water (sometime containing emulsifying chemicals) is pumped into the ground, forcing a free oil phase towards recovery wells. Steam has also been used for enhanced oil recovery.
Soil flushing is generally applicable to soluble organic compounds with octano/water coefficients less than 1 000. Highly water soluble organics, such as low molecular weight alcohols, phenols, carboxylic acids and other organics with a coefficient less than 10 may already have been flushed from the site due to natural flushing processes. Medium solubility organics than could be effectively removed from solids by water flushing include low to medium molecular weight ketones, aldehydes, aromatic, and lower molecular weight alogenated hydrocarbons such as TCE and perchloroethylene (PCE).
Soil flushing is also generally applicable to inorganic compounds with solubility >1 ppm, with soluble salts, such as carbonate of nickel, zinc, copper, and chromates.
Dilute acids, such as acetic acid or dihydrogen phosphate, or chelating agents, such as ethylene diamine triacetic acid (EDTA) or diamene triacetic pyrrolidine acid (DTPA), may be necessary to enhance inorganic solubilization and removal.
Hexavalent chrome and nitrates are amenable to soil flushing because of the negative charge. Dilute acids or reducing agents could change exavalent chrome to the trivalent form and thereby reduce its solubility and, thus, its amenability to soil flushing(but, since the chrome toxicity would be reduced by three orders of magnitude, this would reduce the need for soil flushing).