非水相三氯乙烯与高锰酸盐的反应。

Kim Kyehee, Gurol Mirat D

Department of Civil and Environmental Engineering, San Diego State University, California 92182, USA.

Environ Sci Technol. 2005 Dec 1;39(23):9303-8. doi: 10.1021/es050830i.

Oxidative treatment of trichloroethylene (TCE) in the form of dense nonaqueous-phase liquid (DNAPL) by potassium permanganate (KMnO4) was investigated in a series of batch tests. The study focused on understanding the fundamental mechanisms of oxidative removal of DNAPL TCE by permanganate oxidation. Dissolution experiment for DNAPL TCE has been performed as a control experiment in the absence of KMnO4. DNAPL TCE dissolved into the aqueous phase until it reached the saturation concentration of 1200 mg/L (9.16 x 10(-3) M) at 20 degrees C. The rate of dissolution of DNAPL TCE was proportional to the volume of the DNAPL. In the presence of KMnO4, the experimental results showed that the amount of TCE oxidized during the reaction was increased continuously as [MnO4-] decreased even though the rate decreased as [MnO4-] decreased. It was apparent that more DNAPL TCE was removed with a faster rate for higher initial permanganate concentration. At high permanganate concentration, the aqueous concentration of TCE was kept low and practically constant by the chemical reaction between aqueous TCE and MnO4-. However, as MnO4- was consumed in the system, the aqueous concentration started to increase until it reached solubility. From experimental observation, 1.56-1.78 mol of MnO4- was consumed per mole of TCE oxidized. Furthermore, 2.85-2.98 mol of Cl- was released to the solution per mole of TCE oxidized. Since the complete mineralization of TCE requires 2.0 mol of MnO4- and releases 3 mol of Cl- per mol of TCE oxidized, the observed stoichiometric factors indicated incomplete mineralization of TCE, but nearly complete dechlorination. Enhancement factor due to chemical reaction was quantified experimentally. The enhancement factor was shown to be a function of the molar ratio of MnO4- to TCE in the system, and hence varied during the reaction period.

通过一系列间歇试验研究了高锰酸钾（KMnO₄）对以致密非水相液体（DNAPL）形式存在的三氯乙烯（TCE）的氧化处理。该研究聚焦于理解通过高锰酸盐氧化去除DNAPL TCE的基本机制。已进行了DNAPL TCE的溶解实验作为在无KMnO₄情况下的对照实验。DNAPL TCE溶解到水相中，直到在20℃时达到1200 mg/L（9.16×10⁻³ M）的饱和浓度。DNAPL TCE的溶解速率与DNAPL的体积成正比。在有KMnO₄存在的情况下，实验结果表明，尽管反应速率随着[MnO₄⁻]的降低而降低，但反应过程中被氧化的TCE量随着[MnO₄⁻]的降低而持续增加。显然，对于较高的初始高锰酸盐浓度，更多的DNAPL TCE以更快的速率被去除。在高锰酸盐浓度较高时，水相中的TCE浓度通过水相TCE与MnO₄⁻之间的化学反应保持较低且基本恒定。然而，随着系统中MnO₄⁻被消耗，水相浓度开始增加，直到达到溶解度。从实验观察来看，每氧化1摩尔TCE消耗1.56 - 1.78摩尔的MnO₄⁻。此外，每氧化1摩尔TCE有2.85 - 2.98摩尔的Cl⁻释放到溶液中。由于TCE的完全矿化每氧化1摩尔TCE需要2.0摩尔的MnO₄⁻并释放3摩尔的Cl⁻，观察到的化学计量系数表明TCE未完全矿化，但几乎完全脱氯。通过实验对化学反应增强因子进行了量化。增强因子被证明是系统中MnO₄⁻与TCE摩尔比的函数，因此在反应期间会发生变化。