Changes in chromium distribution during the electrodialytic remediation of a Cr (VI)-contaminated soil |
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Authors: | Ana M Nieto Castillo Juan José Soriano Rafael A García-Delgado |
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Institution: | 1.Instituto Geológico y Minero de Espa?a (IGME), Dept. Investigación y Prospectiva Geocientifica,Madrid,Spain |
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Abstract: | A laboratory study has been carried out to determine the feasibility of in situ remediation of chromium (VI)-contaminated
soil using electrodialysis in relation to its speciation in soil. This technique is best suited for low-permeability soils
or sediments, which may be difficult to remediate by other means and implies the application of a low-intensity direct current
to the soil, which is separated from the electrode compartments by ion-exchange membranes. A clayey soil was prepared for
use in the experiments and was characterized before being mixed with a solution of potassium dichromate for several days to
produce a final Cr content of 4,056 mg/kg of soil dry wt. Remediation tests were carried out under constant-voltage conditions
for periods of 7–14 days and the evolution of applied current to the cell, pH, and conductivity of the electrolytes were recorded
periodically. Fractionation of chromium was determined for soil samples before and after remediation using a standardized
four-step sequential extraction procedure (SEP) with acetic acid, hydroxylamine, hydrogen peroxide, and aqua regia solutions.
Results show that chromium is mobilized from the most labile phases (soluble/exchangeable/carbonate). In a 15 V test, SEP
results show that the amount of chromium extracted in the first step drops from 80% to 9%, but also that changes in the total
chromium distribution occur during the treatment with some transferred to other soil phases that are more difficult to mobilize. |
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Keywords: | Chromium VI Electrodialysis Metal fractionation Soil contamination |
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