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  ELECTROKINETIC REMEDIATION  
 


Electrokinetic remediation is an environmental restoration technique especially designed for the in situ treatment of contaminated soils. The technique is based on the application of a direct electric potential to the contaminated soil by a series of electrodes (anodes and cathodes). The application of the electric potential induces a variety of reactions and transport processes in the contaminated soil, which result in the mobilization and transport of the contaminants towards the anode or cathode electrodes.

 
 

 

1) Soil specimen
2) Porous stones
3) Electrodes
4) Electrode Chambers
5) Auxiliary electrodes
6) Gas Valve

 
  PHYTOREMEDIATION - ELECTROKINETICS  
 

The combination of phytoremediation and electrokinetics has been proposed in an attempt to avoid, in part, the limitations of phytoremediation. Basically, the coupled phytoremediation-electrokinetic technology consists of the application of a low intensity electric field to the contaminated soil in the vicinity of growing plants. The electric field may enhance the removal of the contaminants by increasing the bioavailability of the contaminants. Variables that affect the coupled technology are: the use of AC or DC current, voltage level and mode of voltage application (continuous or periodic), soil pH evolution, and the addition of facilitating agents to enhance the mobility and bioavailability of the contaminants. Several technical and practical challenges still remain that must be overcome through future research for successful application of this coupled technology at actual field sites.

 
  MINE SITE REMEDIATION: Sediments and mine tailings  
 

The removal of heavy metalsfrom acid lake sediment and mine tailing is possible by electrokinetics, although the but the efficiency of the separation is very dependent on the metal speciation in the solid matrix. It is possible to remove heavy metals from fractions I-IV (exchangeable, weakly absorbed, hydrous-oxide bound, organic linked (as described by Tessier et al. 1979) whereas the fraction V (metal in the mineral lattice) is not removed. Preliminary results suggest that the appropriate selection of treatment time and operating conditions may result in an effective removal of the contaminant metals from sediments and mine tailings.

 
  PHYTOCAPPING  
 

Phytocapping is proposed as a practical technology for the remediation of mine tailings and abandoned mine sites. Phytocapping is cost effective, environmental friendly technology and has multifunctional role against to various problems of mine tailings: it provides erosion control, landscape rehabilitation, enhances the soil properties for further colonization of other more demanding vegetal species, reduces the leachability of metals downwards the groundwater, and favors the immobilization of metals forming less bioavailable species. The most critical step in phytocapping is the developing of the first vegetal cover due to the biotoxicity of the mine soil and mine tailings. Several amendment materials can be used to ameliorate the soil conditions creating a favorable environment for the rooting of plants, as well as serving as a source of nutrients. Local plant species with fast growing are preferable for revegetation because they are adapted to the soil and climate conditions.

 
  ELECTRO-BIOREMEDIATION  
 

Bioremediation uses the capability of microorganisms to degrade or remove contaminants in soil and groundwater. The main drawbacks of bioremediation are related with the bioavailability of contaminants, nutrients supply and the availability of electron donors/acceptors as a key element in the metabolic reactions. These limitations can be overcome with the combination of electrokinetics with bioremediation in a coupled technology often called electrobioremediation. Electrokinetics can be used for the effective supply of nutrients or any other compound to improve the microbial activity in the soil. The redox reaction on the electrodes may act as an effective source of electron donors/acceptors for the metabolic reactions. The electric field may also transport bacteria in soil and contaminants, even in short distances, favoring the contaminants to be available for the microorganisms (increasing bioavailability), and the biodegradation rate. The success of the electrobioremediation relies on the enhancing of biodegradation without causing significant damage to the microorganisms. Thus, the main variables that may affect the coupled electrobioremediation technology will be: voltage, current intensity, type of current: AC/DC, mode of operation (continuous, periodic, polarity inversion), electrode nature and stability, addition of nutrients, and other facilitating agents.

 
     
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