Characterization of in situ electroosmosis using conductive fractures

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" Characterization of in situ electroosmosis using conductive fractures "
J.-L. Chen S. M. Islam, Larry

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1112964
Doc. No	:	TLpq304377786
Main Entry	:	J.-L. Chen
	:	S. M. Islam, Larry
Title & Author	:	Characterization of in situ electroosmosis using conductive fractures\ J.-L. ChenS. M. Islam, Larry
College	:	University of Cincinnati
Date	:	1997
student score	:	1997
Degree	:	Ph.D.
Page No	:	132
Abstract	:	Horizontal sheet-like electrodes were used in the field to induce electroosmotic flow in an effort to develop a system for treating shallow contaminated soils using electrokinetics. The system was attached to a DC power supply, creating an electrical gradient of 20 to 31 V/m and a current flux of 4.0 to 5.4 A/m2 within approximately 20 m of soil sandwiched between the electrodes. Electroosmotic flow rates of 0.6 to 0.8 l/hr were observed during tests lasting several weeks, although total flow rate was strongly influenced by fluctuations in the groundwater table. The electrical potential distribution was approximately one-dimensional between the electrodes and changed with energy input in such a way that the electrical gradient increased in the vicinity of the anode, decreased between 0.4 and 1.8 m depth, and was unchanged in the vicinity of the cathode. The exchangeable cation measurements suggest that protons not only exchanged the cations in the diffuse layer but also were adsorbed on the soil minerals, causing the charge density on the soil minerals and ion concentrations of the pore fluid to decrease. The retardation factor for protons calculated from two independent methods ranged between 800 and 8,000, which is 2 to 3 orders greater than that determined from laboratory experiments using kaolinite as the soil medium. The electrical conductivity of the soil as well as the pore fluid was strongly influenced and dominated by the exchange and adsorption of protons. Temperature increased as a result of joule heating. The rate of temperature increase is highest close to center of the fracture-electrode due to the sharp convergence of the electrical potential. There was also significant increase of temperature outside the edge of the mesh-electrode. Numerical model is able to simulated the pattern and magnitude of the temperature observation during the test. Piezometric head decreased by less than 10 cm close to the mesh-electrode and increased between 2 to 6 cm close to the fracture-electrode. The change in piezometric head is consistent with established theories. Comparison between the model simulation and the observed piezometric head changes suggests that the hydraulic conductivity of the soil underneath the mesh-electrode decreased due to consolidation by electroosmosis.
Subject	:	Biological sciences
	:	Earth sciences
	:	Environmental science
	:	groundwater remediation
	:	Health and environmental sciences
	:	soil remediation