Louisiana State University and Agricultural & Mechanical College

Electrokinetics, Inc.

Robert J Gale

Yalcin B Acar

Robert E Marks

Suitable electrolyte conditioning at the electrodes greatly facilitates the transport of desired ions through soil, enhancing the ability of electrokinetic processes to stabilize the soil through cementing reactions. Cationic species are injected at the anode, and anionic species at the cathode, with suitable electrolyte conditioning. For example, if acid or base formation negatively affects transport, chemical conditioning is used to neutralize the acid or base products of electrolysis. Ionic species can be transported through soil at rates of several centimeters a day, even in soils such as clays having a low hydraulic conductivity. Electroosmotic transport can be minimized by appropriate conditioning of the pore fluid chemistry. For example, placement of chemical conditioners with smaller cations at the anode compartment and larger anions at the cathode compartment, or increasing the ion content of the pore fluid (e.g. by acidification) can help minimize electroosmotic transport and any of its adverse effects on species transport. The cations and anions are preferably selected to form cementatious precipitates in the soil. Thus when cationic species are injected at the anode and anionic species are injected at the cathode, stabilization reactions can prevail in the soil as the result of cross-transport of species, and a homogenous and uniform cementation and stabilization can be achieved in a short time.

Electrochemical stabilization of soils and other porous media

The invention relates to insitu bio-electrokinetic remediation of contaminated soil containing hazardous mixed wastes as organic pollutants and hazardous heavy metals. Bio-remediation of the organic pollutants is followed by removal of the hazardous material. Cultured micro-organisms, nutrients and growth factors are added to clean soil adjacent to contaminated soil. Positive anodes and negative cathodes are placed in the microbial-loaded clean soil adjacent to the contaminated soil. The negative cathode is closest to the interface of the clean and contaminated soil. DC current is applied between the electrodes and water containing cultured microorganisms is pushed by the electrokinetic pumping effect into the contaminated site. The acid generated at the anode is not allowed to enter the contaminated soil. Cultured microorganisms are introduced into clean soil on the opposite side of the contaminated soil. DC current is reversed to change the original anode to cathode and cathode to anode. Micro-organism laden water is pulled into the contaminated site. The push-pull current reversal process is repeated to increase insitu biodegradation efficiency. When the biological oxidation of organic pollutants is complete, the acid front enters the contaminated soil for removal of hazardous metals. Hazardous metals precipitate near or electroplate on the cathode or are recovered from fluid collected at the cathode. Solubilizing materials are added to the water near the cathode to minimize the precipitation reaction. Fluids collected at the cathode are pumped through a treatment system before water is returned to the soil.

Insitu bio-electrokinetic remediation of contaminated soils containing

The electrochemical decontamination of soil or slurries through the use of an inert anode, a nonreactive cathode, and supplying water to the soil near the anode.

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Baton Rouge, LA, United States of America

Robert J Gale