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Electrolytic transformation of ordinance related compounds (ORCs) in groundwater: Laboratory mass balance studies
Electrolytic reactive barriers (e − barriers) consist of closely spaced permeable electrodes installed across a groundwater contaminant plume in a permeable reactive barrier format. Application of sufficient potential to the electrodes results in sequential oxidation and reduction of the target cont...
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Published in: | Chemosphere (Oxford) 2006-02, Vol.62 (5), p.689-698 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Electrolytic reactive barriers (e
− barriers) consist of closely spaced permeable electrodes installed across a groundwater contaminant plume in a permeable reactive barrier format. Application of sufficient potential to the electrodes results in sequential oxidation and reduction of the target contaminant. The objective of this study was to quantify the mass distribution of compounds produced during sequential electrolytic oxidation and reduction of ordinance related compounds (ORCs) in a laboratory analog to an e
− barrier. In this study, a series of column tests were conducted using RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) and TNT (2,4,6-trinitrotoluene) as representative ORCs. The experimental setup consisted of a plexiglass column packed with quartz–feldspar sand to simulate aquifer conditions. A single set of porous electrodes consisting of expanded titanium-mixed metal oxide mesh was placed at the midpoint of the sand column as a one-dimensional analog to an e
− barrier. Constant current of 20
mA (variable voltage) was applied to the electrode set. Initial studies involved quantification of reaction products using unlabeled RDX and TNT. Approximately 70% of the influent concentration was transformed, in one pass, through sequential oxidation–reduction for both contaminants. Following the unlabeled studies,
14C labeled RDX and TNT were introduced to determine the mass balance. An activity balance of up to 96% was achieved for both
14C-RDX and
14C-TNT. For both contaminants, approximately 21% of the influent activity was mineralized to
14CO
2. The proportion of the initial activity in the dissolved fraction was different for the two test contaminants. Approximately 30% of the initial
14C-RDX was recovered as unreacted in the dissolved phase. The balance of the
14C-RDX was recovered as non-volatile, non-nitroso transformation products. None of the
14C-RDX was sorbed to the column sand packing. For
14C-TNT approximately 51% of the initial activity was recovered in the dissolved phase, the majority was unreacted TNT. The balance of the
14C-TNT was either sorbed to the sand packing (approximately 24%) or dissolved/mineralized as unidentified ring cleavage products (∼4%). |
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ISSN: | 0045-6535 1879-1298 |
DOI: | 10.1016/j.chemosphere.2005.06.012 |