title: Manganese valence in oxides formed from in situ chemical oxidation of TCE by KMnO4.
abstract: Batch and column experiments designed to simulate in situ chemical oxidation (ISCO) in a sand aquifer were conducted to create Mn-oxides (MnOx) by oxidation of trichloroethylene (TCE) with permanganate (MnO4-). Electron energy-loss spectroscopy (EELS) and X-ray photoelectron spectroscopy (XPS) were used to quantify Mn valence in the oxides. The valence of Mn in the MnOx generated in near-source ISCO conditions was 2.2 and 2.3 when formed at low (<3) and neutral (6-7) pH conditions, respectively. There is no significant difference between these values. Valence was found to be sensitive to the preparation method and to aging. When formed in the presence of excess MnO4-, or aged for 3 months, Mn valence ranged from 2.5 to 3.6. Aging in a lower pH environment inhibited Mn oxidation. The EELS and XPS methods provided similar results, but there was a slight bias to higher values for XPS. This work demonstrates that MnO2(s) may not be the main product of MnO4- reaction with chlorinated solvents as is commonly assumed and that the efficiency of ISCO treatment may be greater than previously known.
authors.affiliation: Department of Geology, University of New Brunswick, P.O. Box 4400, Fredericton, New Brunswick E3B 5A3, Canada. dloomer@unb.ca
authors.forename: Diana B
authors.initials: DB
authors.lastname: Loomer
authors.forename: Tom A
authors.initials: TA
authors.lastname: Al
authors.forename: Vernon J
authors.initials: VJ
authors.lastname: Banks
authors.forename: Beth L
authors.initials: BL
authors.lastname: Parker
authors.forename: K Ulrich
authors.initials: KU
authors.lastname: Mayer
mesh_terms: D008345:Manganese / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000138:chemical synthesis / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D011196:Potassium Permanganate / Q000737:chemistry*; D046590:Spectroscopy, Electron Energy-Loss; D014241:Trichloroethylene / Q000737:chemistry*
chemical_list: D010087:Oxides; D011196:Potassium Permanganate; D014241:Trichloroethylene; D008345:Manganese