Zhai Xihong, Hua Inez, Rao P Suresh C, Lee Linda S
School of Civil Engineering, 550 Stadium Mall Drive, Purdue University, West Lafayette, IN 47907, USA.
J Contam Hydrol. 2006 Jan 5;82(1-2):61-74. doi: 10.1016/j.jconhyd.2005.08.007. Epub 2005 Oct 17.
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.
开展了一项实验室研究，以考察使用高锰酸钾（KMnO₄）通过助溶剂强化的原位化学氧化（ISCO）去除全氯乙烯（PCE）的效果。这项新技术的概念基础是通过添加助溶剂来增强高锰酸钾对致密非水相液体（DNAPL）的氧化作用，从而提高DNAPL的溶解度，同时避免其迁移。在筛选的17种助溶剂候选物中，叔丁醇（TBA）和丙酮在高锰酸钾存在的情况下最为稳定，二者均显著提高了PCE的水溶解度，因此适合在本研究中用作助溶剂。批次实验表明，在纯水溶液（无助溶剂）中，高锰酸钾氧化PCE的二级反应速率常数为0.043±0.002 M⁻¹ s⁻¹。在存在20%助溶剂（体积分数=fc=0.2）的情况下，使用TBA时反应速率常数降至0.036±0.003 M⁻¹ s⁻¹，使用丙酮时降至0.031±0.002 M⁻¹ s⁻¹。然而，在存在游离相PCE的情况下，丙酮/水溶液（fc=0.2）中PCE氧化产生的氯离子浓度约为水溶液中的两倍，这表明PCE溶解度的增加足以弥补反应速率常数的降低，因此助溶剂提高了PCE的氧化效率。在水体系中观察到了完整的氯质量平衡，而在TBA/水或丙酮/水（fc=0.2）体系中约为70%。在含有残留DNAPL并采用fc助溶剂逐步增加的等度冲洗的土壤柱中，fc=0.2时的TBA导致PCE迁移，而fc≤0.5时的丙酮则不会。因此，尽管TBA和丙酮都表现出相似的溶解度增强效果，但丙酮可能是用于DNAPL源区原位修复的更好溶剂选择。
