To provide a more complete understanding of the kinetics of in situ chemical oxidation (ISCO) with permanganate (MnO4-), we measured the kinetics of oxidation of 24 contaminants-many for which data were not previously available. The new data reported here were determined using an efficient method based on continuous measurement of the MnO4 - concentration by absorbance spectrometry. Under these conditions, the kinetics were found to be first-order with respect to both contaminant and MnO4- concentrations, from which second-order rate constants (k″) were readily obtained. Emerging contaminants for which k″ was determined (at 25 °C and pH 7) include 1,4-dioxane (4.2 × 10-5 M-1 s-1), methyl t-butyl ether (MTBE) (1.0 × 10-4 M-1 s-1), and methyl ethyl ketone (MEK) (9.1 × 10-5 M-1 s-1). Contaminants such as 2,4,6-trinitrotoluene (TNT), the pesticides aldicarb and dichlorvos, and many substituted phenols are oxidized with rate constants comparable to tetrachloroethene (PCE) and trichloroethene (TCE) (i.e., 0.03-1 M-1 s-1) and therefore are good candidates for remediation with MnO4- in the field. There are several-sometimes competing-mechanisms by which MnO4- oxidizes contaminants, including addition to double bonds, abstraction of hydrogen or hydride, and electron transfer.
ASJC Scopus subject areas
- Environmental Chemistry