Date of Award

1994

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Advisor

Yalcin B. Acar

Abstract

A mathematical model is formulated for multicomponent transport of reactive species under an electric field. A set on differential and algebraic equations is developed for transport of fluid, charge, and species in a saturated soil under coupled hydraulic, electric, and chemical potential gradients. An iterative scheme is chosen in solution of a system of differential and algebraic equations. Six differential equations and four algebraic equations are used to model transport of $Pb\sp{2+}$, $H\sp+$, $OH\sp-$, $NO3\sp-$, the associated chemical reactions, electric potential and the hydraulic head across the electrodes. Finite Element Method is used in space discretization. Finite difference technique is used in time discretization. Three unenhanced pilot-scale tests, using about one ton soil specimens, are conducted to investigate the effect of up-scaling bench-scale tests, to evaluate the feasibility and cost efficiency of electrokinetic soil remediation at dimensions representative of field conditions, and to assess the hypothesized principles of multicomponent species transport under an electric field. Two of these tests are conducted on kaolinite specimens spiked with lead nitrate solution at lead concentrations of 856 $\mu g/g$ and 1,533 $\mu g/g$. The third test is conducted on kaolinite/sand mixture loaded with lead at a concentration of 5,322 $\mu g/g$. A direct current density of 133 $\mu A/cm\sp2$ is maintained across the soil in all pilot-scale tests. Pilot-scale tests demonstrate significant lead removal from soil, up to 98% except the soil zone in direct contact with the cathode. Energy expenditure in these tests is within the range of 300 to 700 kWh/$m\sp3$. The results demonstrate the feasibility of using electrokinetics for full-scale in-situ remediation of heavy metals from soil. Model predictions show very good agreement with the pilot-scale test results. This agreement demonstrates the validity of the formalisms offered for multicomponent transport of reactive species under an electric field and reinforces the validity of the hypothesized principles of electrokinetic remediation.

Pages

396

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