Document Detail

DNAPL remediation with in situ chemical oxidation using potassium permanganate. Part I. Mineralogy of Mn oxide and its dissolution in organic acids.
MedLine Citation:
PMID:  14698870     Owner:  NLM     Status:  MEDLINE    
Previous studies on in situ chemical oxidation of trichloroethylene (TCE) with potassium permanganate indicated that the solid reaction product, Mn oxide, could reduce the permeability of the porous medium and impact the success of dense non-aqueous phase liquid (DNAPL) removal. In order to address the issue of permeability reduction caused by precipitation, this study investigated the mineralogy of Mn oxides and the possibilities of removing the solid precipitates by dissolution. The solid reaction product from the oxidation of TCE by permanganate is semi-amorphous potassium-rich birnessite, which has a layered mineral structure with an interlayer spacing of 7.3 A. The chemical formula is K(0.854)Mn(1.786)O(4).1.55H(2)O. It has a relatively small specific surface area at 23.6+/-0.82 m(2)/g. Its point of zero charge (pzc) was measured as 3.7+/-0.4. This birnessite is a relatively active species and could participate in various reactions with existing organic and inorganic matter. The dissolution kinetics of Mn oxide was evaluated in batch experiments using solutions of citric acid, oxalic acid, and ethylenediaminetetraacetic acid (EDTA). Initial dissolution rates were determined to be 0.126 mM/m(2)/h for citric acid, 1.35 mM/m(2)/h for oxalic acid, and 5.176 mM/m(2)/h for EDTA. These rates compare with 0.0025 mM/m(2)/h for nitric acid at pH=2. Organic acids dissolve Mn oxide quickly. Reaction rates increase with acid concentration, as tested with citric acid. The dissolution mechanism likely involves proton and ligand-promoted dissolution and reductive dissolution. Citric and oxalic acid can induce ligand-promoted dissolution, while EDTA can induce ligand-promoted and reductive dissolutions. At low pH, proton-promoted dissolution seems to occur with all the acids tested, but this process is not dominant. Reductive dissolution appears to be the most effective process in dissolving the solid, followed by ligand-promoted dissolution. These experiments indicate the significant potential in using these organic acids to remove precipitates formed during the oxidation reaction.
X David Li; Franklin W Schwartz
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Journal of contaminant hydrology     Volume:  68     ISSN:  0169-7722     ISO Abbreviation:  J. Contam. Hydrol.     Publication Date:  2004 Jan 
Date Detail:
Created Date:  2003-12-30     Completed Date:  2004-05-14     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  8805644     Medline TA:  J Contam Hydrol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  39-53     Citation Subset:  IM    
Department of Geological Sciences, The Ohio State University, Columbus, OH 43210, USA.
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MeSH Terms
Chemical Precipitation
Hydrogen-Ion Concentration
Manganese Compounds / analysis*
Oxides / analysis*
Potassium Permanganate / chemistry*
Water Pollution / prevention & control*
Reg. No./Substance:
0/Manganese Compounds; 0/Oxides; 1317-35-7/manganese oxide; 7722-64-7/Potassium Permanganate

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