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Title: Electrokinetic remediation of soils contaminated with electroplating wastes

Abstract

Electrokinetic remediation of soils simulated with electroplating waste contamination was investigated in two soils, kaolin and glacial till. Soil samples were contaminated with nickel, cadmium and hexavalent chromium and subjected to an external electric field for four days. Results of these experiments revealed that the soil composition plays an important role in electrokinetic remediation. Due to induced electric potential, a distinct pH gradient was developed in kaolin; however, in glacial till alkaline conditions existed throughout the soil because of its high carbonate buffering capacity. The movement of cationic metallic contaminants, Ni(II) and Cd(II), from the anode to the cathode was significant in kaolin as compared to glacial till. Because of high pH conditions near the cathode, Ni(II) and Cd(II) were precipitated in kaolin. In glacial till, however, because of alkaline conditions throughout the soil, most of Ni(II) and Cd(II) precipitated without migration. Overall, this study demonstrates that anion exchange, cation exchange and precipitation were the significant fixation mechanisms of nickel, cadmium and chromium in soils.

Authors:
;  [1];  [2]
  1. Univ. of Illinois, Chicago, IL (United States). Dept. of Civil and Materials Engineering
  2. Patterson Associates Inc., Chicago, IL (United States)
Publication Date:
OSTI Identifier:
376161
Report Number(s):
CONF-960426-
Journal ID: ISSN 0097-2126; TRN: IM9642%%249
Resource Type:
Conference
Resource Relation:
Conference: 58. annual meeting of the American power conference, Chicago, IL (United States), 9-11 Apr 1996; Other Information: PBD: 1996; Related Information: Is Part Of Proceedings of the American Power Conference. Volume 58-I; McBride, A.E. [ed.]; PB: 767 p.
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; SOILS; REMEDIAL ACTION; INDUSTRIAL WASTES; REMOVAL; NICKEL; CADMIUM; CHROMIUM; LAND RECLAMATION; ELECTRODYNAMICS; FARADAY INDUCTION; ELECTRIC POTENTIAL; SOIL CHEMISTRY

Citation Formats

Reddy, K.R., Parupudi, U.S., and Devulapalli, S. Electrokinetic remediation of soils contaminated with electroplating wastes. United States: N. p., 1996. Web.
Reddy, K.R., Parupudi, U.S., & Devulapalli, S. Electrokinetic remediation of soils contaminated with electroplating wastes. United States.
Reddy, K.R., Parupudi, U.S., and Devulapalli, S. 1996. "Electrokinetic remediation of soils contaminated with electroplating wastes". United States. doi:.
@article{osti_376161,
title = {Electrokinetic remediation of soils contaminated with electroplating wastes},
author = {Reddy, K.R. and Parupudi, U.S. and Devulapalli, S.},
abstractNote = {Electrokinetic remediation of soils simulated with electroplating waste contamination was investigated in two soils, kaolin and glacial till. Soil samples were contaminated with nickel, cadmium and hexavalent chromium and subjected to an external electric field for four days. Results of these experiments revealed that the soil composition plays an important role in electrokinetic remediation. Due to induced electric potential, a distinct pH gradient was developed in kaolin; however, in glacial till alkaline conditions existed throughout the soil because of its high carbonate buffering capacity. The movement of cationic metallic contaminants, Ni(II) and Cd(II), from the anode to the cathode was significant in kaolin as compared to glacial till. Because of high pH conditions near the cathode, Ni(II) and Cd(II) were precipitated in kaolin. In glacial till, however, because of alkaline conditions throughout the soil, most of Ni(II) and Cd(II) precipitated without migration. Overall, this study demonstrates that anion exchange, cation exchange and precipitation were the significant fixation mechanisms of nickel, cadmium and chromium in soils.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1996,
month =
}

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  • An electrokinetic process for remediation of mercury contaminated soils using an iodine-iodide lixiviant was developed. In this process, reduced forms of insoluble mercury are oxidized by iodine. Iodide then reacts with mercury to form the highly soluble HgI{sub 4}{sup 2-} complex, which in turn migrates toward the anode via electromigration. The objective was to determine the thermodynamic conditions under which mercury could be solubilized and transported from the soil. At the end of the electrokinetic treatment process, pH, pE, iodine, iodide, and soluble and total mercury were measured along the length of the soil. The process was tested on amore » soil contaminated with HgS (cinnabar) in the laboratory and a contaminated soil obtained from a hazardous waste site. Up to 99% overall removal of mercury could be achieved from the laboratory contaminated soil. Up to 84% of mercury was removed from some sections of the field contaminated soil, but overall removal was only 6%. The presence of iodine in the soil pore water was found to be the most important factor in solubilization of mercury. Residual levels of soluble Hg remaining in soil after treatment were greater than allowed by current regulations and far in excess of the solubility of Hg compounds present in the untreated soil.« less
  • Electrokinetic remediation of contaminated soil has been demonstrated for saturated and unsaturated sand in preliminary experiments using a novel transport visualization technique. Large anionic organic dyes were mixed with a portion of soil and the rate of electromigration of the dye in an imposed electric field was monitored photographically. One of the fastest current-normalized electromigration rates was measured in the driest sand, which contained 7% water by weight. This moisture content is typical of the moisture content in the unsaturated zone of subsurface native soils found in New Mexico. The characteristics of the electromigration were similar in both the saturatedmore » and unsaturated sand. The leading edge of the dye migration front was diffuse while the trailing edge was sharp and concentrated. This and other observed behavior may indicate a concentration effect, where the electromigration rate of dilute dye is greater than that of concentrated dye. The soil left after the trailing edge passed seemed to contain no residual dye in both the saturated and unsaturated cases. The success of demonstrating electromigration of large molecules in unsaturated soil is encouraging and indicates that it may be feasible to remediate in situ anionic heavy metals such as chromate from unsaturated soil with electrokinetic techniques. 23 refs., 7 figs.« less
  • This research was carried out to evaluate feasibility of using an electrokinetic technique to remove hydrophobic organic pollutants from soils, with the assistance of a cosolvent (n-butylamine, tetrahydrofuran, or acetone) added to the conducting fluid. The experiments were carried out on glacial till clay with phenanthrene as the test compound. Desorption equilibrium was investigated by batch tests. The electrokinetic experiments were conducted using a 19.1 cm long x 6.2 cm inside diameter column under controlled voltage. Water or 20% (volume) cosolvent solution was constantly supplied at the anode. The concentration of phenanthrene in the effluent collected at the cathode wasmore » monitored. Each experiment lasted for 100 to 145 days. Results showed that the presence of n-butylamine significantly enhanced the desorption and electrokinetic transport of phenanthrene; about 43% of the phenanthrene was removed after 127 days or 9 pore volumes. The effect of acetone was not as significant as butylamine. The effluent flow in the tetrahydrofuran experiments was minimal, and phenanthrene was not detected in the effluent. The use of water as the conducting solution did not cause observable phenanthrene migration.« less
  • In-situ remediation of mercury-contaminated soils, by electrokinetic or other means, is difficult because of the low solubility of mercury and its compounds. In this research, enhanced electrokinetic remediation of HgS-contaminated soils using I{sub 2}/I{sup -} lixiviant was investigated using bench-scale electrokinetic cells. The thermodynamic conditions under which the lixiviant could be effective were determined by constructing a pE-pH diagram for the Hg-S-I system. Introduced near the cathode, the lixiviant migrated through the soil to the anode by electromigration. Mercury, released by the oxidation of HgS compounds by I{sub 2}, was complexed as HgI{sub 4}{sup 2-}. The negative complex continued tomore » electromigrate toward the anode. Up to 99% of the Hg present in laboratory-contaminated soils could be removed. Electrokinetic treatment of a field-contaminated soil, containing more organic matter than the laboratory-contaminated soil, occurred much slower. The critical issues in determining the efficacy of the process are the oxidation of reduced Hg by I{sub 2} and I{sub 3}{sup -} and the transport of the resultant HgI{sub 4}{sup 2-} complex. 17 refs., 7 figs., 2 tabs.« less