Soil pollution decontamination

Berthet, B., C. Amiard-Triquet, and R. Martoja. 1990. Effets chimiques et histologiques de la decontamination de l huitre Crassostrea gigas Thurberg prealablement exposee a 1 argent. Water Air Soil Pollut. 50 355-369. 

Vasylyeva T., Duka E., Kharitonov N., 1995, Relation between polluted soils and health of population and rehabilitation measures, International Workshop on Technologies for Decontamination and Remediation of Soils Polluted by Chemical products, Paris -France... 

Risoul, V., Renauld, V., Trouve, G., and Gilot, P. (2002). A laboratory pilot study of thermal decontamination of soils polluted by PCBs. Comparison with thermogravimetric analysis. Waste Manage. 22(1), 61-72. 

These enzymes are promising for destruction of chemical weapons stockpiles, soil remediation, decontamination of materials, protective equipment, and water polluted by pesticides and nerve agents (Russel et al, 2003). In particular, phosphorothiolates such as VX are relatively resistant to PTE. Thus, oxidative cleavage of the P-S bond could be achieved by oxidases like laccases. These enzymes could be used in association with other OP-degrading enzymes for skin decontamination or in topical skin protection formulations. Though no work has been performed on combined action of oxidases and hydrolases, oxidation of P-bonded alkyl/aryl chains by oxidases is expected to alter enantio-selectivity of PTE for parent OPs, and therefore to improve the efficiency of catalytic bioscavengers. 

Hansen HK, Ottosen LM, Lauesen S and ViL-lumsen a (1997) Electrochemical analysis of ion-exchange membranes with respect to a possible use in electrodialytic decontamination of soil polluted with heavy metals. Separation Sci Technol 32 2425 — 2444. 

Tafesse, F. and Mndubu, Y. 2007. Iron promoted decontamination studies of nitrop-henylphosphate in aqueous and microemulsion media A model for phosphate ester decontamination. Water Air Soil Pollut, 183, 107-113. 

TeRRox A process for decontaminating soil which has been polluted by hydrocarbons by treating it with hydrogen peroxide. Developed by DeGussa and operated at its plant in Knapsack, Germany, from 1996. 

The use of catalysts for exploiting renewable energy sources, producing clean fuels in refineries, and minimizing the by-product formation in industry also fall within the definition of environmental catalysis. In the future, the continuous effort to control transport emissions, improve indoor ah quality, and decontaminate polluted water and soil will further boost catalytic technology. All in all, catalysts will continue to be a valuable asset in the effort to protect human health, the natural environment, and the existence of life on Earth. 

The studies with sediment cultures indicate natural degradation potential for aquatic sediments exposed to anthropogenic CP pollution. However, in situ remediation rates for CP-contaminated sediments may be difficult to enhance. Possibilities involve nutrient and electron donor/acceptor amendments. Ex situ remediation could involve sediment dredging and application of methods developed for soil decontamination, such as slurry reactors and composting. 

In 2002, an interesting concept was proposed for coupling a C02-based supercritical extraction with air oxidation in order to remove and decompose pollutants from gases or liquids (134). An exemplary process scheme according to this preliminary concept is shown in Figure 5. Possible (future) environmental applications of such an integrated supercritical extraction-reaction system include treatment of liquid effluents, regeneration of catalysts and adsorption materials, and soil decontamination. 

In early works, contaminated soils were slurried in NH3(1) at ambient temperature and, after premixing, a weighed quantity of solid Na or Ca was dropped directly into the stirring slurry. The metal quickly dissolved. Conductivity and calorimetry showed that the reactions were completed within a few seconds. Reactions of neat PCBs and CAHs are exothermic, but NH3 reflux can be used to control the exotherm. In soil, sludge, and related decontaminations, the pollutants are diluted in the matrix and are then more highly diluted in the NH3 slurry. Thus, exotherms are not a problem. Typically, the volume of NH3 used is twice that of the soil volume. 

Another very important green chemistry solvent is supercritical water (SCW) [14], Water under supercritical conditions is an extremely powerful oxidizing and cleansing agent that has been proven remarkably promising as a soil decontaminant by efficiently degrading persistent organic toxic wastes that are difficult to eliminate from polluted soils, and in the treatment of several types of industrial wastes such as textile and cellulose wastewater [2],... 

Electroremediation — Electrochemical process for in-situ decontamination and restoration of polluted soils, sludge, or other solid wastes. It is also currently known as electroreclamation, electrorestoration, or electrokinetic remediation. The technology involves the application of a low-intensity direct current across inert electrode pairs... 

One of the more recent technologies in pollution treatment and remediation is based on the electrokinetic decontamination of soils [126-128], in which a dc potential (a few volts per centimeter) is applied across two inert electrodes embedded in a soil mass. This applied potential causes decomposition of the soil water to occur at the two electrodes. The migration of contaminants in the electric field, water transport, and reactions at the electrodes, as well as reactions caused by the induced pH gradient, can effectively clean soils. Acar et al. [127] reviewed electrokinetic remediation for the removal of metals and other inorganic contaminants from soil as well as its use in the extraction of organics from contaminated soils. 

The process of ED is, by definition, a membrane-based separation process in which ions are driven through an ion-selective membrane under the influence of an electric field [35]. Conversely, in electrofiltration a charged pollutant particle is prevented from moving through a membrane by the influence of an electric field. Electrosorption is an electrically enhanced ion-exchange process and electroremediation is a process developed for the decontamination of polluted soil. Each different process is discussed separately. 

Electroremediation using electrical current is the final purification method discussed in this chapter. Here, an array of anodes are placed in the soil opposite an array of cathodes. When electric potential is apphed the following processes occur electrolysis of water in the soil, dissolution of polluting ions, migration of ions under the influence of the apphed potential field, and reduction or pH based precipitation at the cathode [68,69]. This technique, also known as electroreclamation or electrochemical soil decontamination, does not require a membrane however, improved electroremediation has been reported when ion-exchange membranes were incorporated into the system [70]. The function of the membrane is to retain OH ions produced at the cathode. Migration of these OH ions is prevented to avoid precipitation of the heavy metal ions in the sod. 

Elliott, H.A. Peters, R.W. "Decontamination of Metal-Polluted Soils Using Chelating Agents, In Removal of Heavy Metals from Groundwaters CRC Press, Inc. Boca Raton, FL, (in press). 

Elliott. H. A.. Linn, J. H. and Shields, G. A.(1989). Role of Fe in extractive decontamination of Pb polluted soils. Hazard Waste Hazard Mater. 6. 223-228. 

Surfactants and microemulsion systems can be used for ex situ treatment of contaminated soil or in situ soil decontamination. In situ remediation is usually preferred if excavation of the contaminated soil is not possible or expensive, e.g. beneath buildings or for contaminations at great depth. Often bioremediation or natural attenuation is used for decontamination. In most cases, these techniques only permit the effective degradation of contaminants in the plume formed by dissolved pollutants which may be very large. However, for the remediation of a contaminated site, it is also necessary to remove the source where the pollutants maybe adsorbed in large quantities or may be present as solid or liquid phases. The latter are called NAPL (non-aqueous phase liquids) and a differentiation is made between LNAPL (light non-aqueous phase liquids) with a lower density than water and DNAPL (dense non-aqueous phase liquids) with a higher density than water (see Fig. 10.1). 

The choice of suitable surfactants and additional chemicals for the decontamination of source zones largely depends on the type of pollutant and the structure of the soil (mainly on adsorption behaviour and hydraulic conductivity). Adsorbed and solid pollutants or very viscous liquid phases cannot be mobilised. Preformed microemulsions, co-solvents or co-surfactants can be favourably used for such contaminations in order to enhance the solubilisation capacity of surfactants. NAPL with low viscosity can easily be mobilised and also effectively solubilised by microemulsion-forming surfactant systems. Mobilisation is usually much more efficient. It is achieved by reducing the interfacial tension between NAPL and water. Droplets of organic liquids, which are trapped in the pore bodies, can more easily be transported through the pore necks at lower interfacial tension (see Fig. 10.2). The onset of mobilisation is determined by the trapping number, which is dependent on... 

In conclusion, PAH and soil evolution indexes are simple and rapid tools for the characterisation of PAH-contaminated soils in terms of level and repartition of pollution and for the prediction of their potential biotreatability. From an environmental point of view, they permit pointing out sensitive zones and defining priorities in terms of decontamination. 

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