Effect of voltage gradient on integrated 

electrochemical remediation of contaminant 

mixtures

Krishna R. Reddy and Madhusudhana R. Karri

Abstract

This paper evaluates the effect of voltage gradient on the efficiency of integrated electrochemical 

remediation (IECR) of low permeability soils contaminated with both heavy metals and polycyclic 

aromatic hydrocarbons (PAHs). The IECR remediation process aims to oxidize organic

contami

nants within the soil by the electro-osmotic delivery of hydrogen peroxide (H2O2) and a Fenton-like 

oxidation process, as well as simultaneously removing heavy metals by electro-osmotic advection 

and electromigration. In Fenton-like oxidation, the native soil iron is utilized as a catalyst to

decom

pose  H2O2 to generate free hydroxyl radicals that oxidize PAHs into relatively benign products such 

as carbon dioxide, water and oxygen. A series of bench-scale experiments was performed on kaolin 

(a low permeability soil) spiked with nickel (a representative heavy metal) and phenanthrene (a 

rep

resentative PAH) each at a concentration of 500 mg per kg of dry soil under two voltage gradients, 1 

and 2 VDC/cm. The

H2O2 solution in two different concentrations at 5% and 10% was introduced at 

the anode, and each experiment was conducted for a total duration of four weeks. The results 

showed that increasing the voltage gradient from 1 VDC/cm to 2 VDC/cm did not increase the 

elec

tro-osmotic delivery of H2O2 significantly. Phenanthrene removal from the soil was negligible in all 

the experiments; however, 28% and 34% of the phenanthrene were oxidized within the soil in the 5% 

and 10% 

H2O2 experiments, respectively, under 1 VDC/cm. The phenanthrene oxidation increased 

to about 32% and 42% under 5% and 10% 

H2O2 concentrations, respectively, under 2 VDC/cm. 

Nickel migrated towards the cathode and then precipitated close to the cathode, due to high pH 

con

ditions in all the experiments. Nickel migration was slightly higher in the case of 2 VDC/cm than in 

the case of 1 VDC/cm, due to greater migration of the acidic pH front towards the cathode under 2 

VDC/cm. Overall, the results showed that an increase in the voltage gradient from 1 VDC/cm to 2 

VDC/cm improved overall remedial performance slightly, and alternative strategies to increase 

H2O2 

delivery and prevent precipitation of metals near the cathode are required for achieving significantly 

higher remedial efficiencies.

Key words: chemical oxidation, clays, contaminant mixtures, electrokinetic remediation, heavy 

metals, organic contaminants, soil

© 2007 EPP Publications Ltd

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