title: Cosolvent-enhanced chemical oxidation of perchloroethylene by potassium permanganate.
abstract: A laboratory study was conducted to examine cosolvent-enhanced in-situ chemical oxidation (ISCO) of perchloroethylene (PCE) using potassium permanganate (KMnO4). The conceptual basis for this new technique is to enhance permanganate oxidation of dense non-aqueous phase liquids (DNAPLs) with the addition of a cosolvent, thereby increasing DNAPL solubility while avoiding mobilization. Among 17 cosolvent candidates screened, tertiary butyl alcohol (TBA) and acetone were the most stable in the presence of KMnO4, both of which increased PCE aqueous solubility significantly, and therefore are suitable to be used as cosolvent in this study. Batch experiments indicated that the second-order rate constant for PCE oxidation by potassium permanganate was 0.043+/-0.002 M(-1) s(-1) in the purely aqueous (no cosolvent) solution. In the presence of 20% cosolvent (volume fraction=fc=0.2), the rate constant decreased to 0.036+/-0.003 M(-1) s(-1) with TBA and to 0.031+/-0.002 M(-1) s(-1) with acetone. However, in the presence of free-phase PCE, chloride ion concentration from PCE oxidation in acetone/water solutions (fc=0.2) was about twice that in aqueous solutions, indicating that the increase in PCE solubility more than compensated for the decrease in reaction rate constant, such that the oxidation efficiency of PCE was increased with cosolvent. A complete chlorine mass balance was observed in the aqueous system, whereas approximately 70% was obtained in TBA/water or acetone/water (fc=0.2). In soil columns containing residual DNAPL and subjected to isocratic flushing with step-wise increases in f(c) cosolvent, TBA at fc=0.2 resulted in PCE mobilization, whereas acetone at fc<or=0.5 did not. Therefore, although both TBA and acetone exhibit similar solubility enhancements, acetone may be a better solvent choice for use in in-situ remediation of DNAPL source zones.
authors.affiliation: School of Civil Engineering, 550 Stadium Mall Drive, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Xihong
authors.initials: X
authors.lastname: Zhai
authors.forename: Inez
authors.initials: I
authors.lastname: Hua
authors.forename: P Suresh C
authors.initials: PS
authors.lastname: Rao
authors.forename: Linda S
authors.initials: LS
authors.lastname: Lee
mesh_terms: D000096:Acetone / Q000737:chemistry; D004787:Environmental Pollution / Q000517:prevention & control*; D010084:Oxidation-Reduction; D011196:Potassium Permanganate / Q000737:chemistry*; D012989:Soil Pollutants; D012995:Solubility; D013750:Tetrachloroethylene / Q000737:chemistry*; D013997:Time Factors; D014874:Water Pollutants, Chemical; D020002:tert-Butyl Alcohol / Q000737:chemistry
chemical_list: D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D011196:Potassium Permanganate; D000096:Acetone; D020002:tert-Butyl Alcohol; D013750:Tetrachloroethylene