Thermally activated persulfate oxidation of trichloroethylene (TCE) and 1,1,1-trichloroethane (TCA) in aqueous systems and soil slurries
Thermally activated persulfate oxidation of trichloroethylene (TCE) and 1,1,1-trichloroethane (TCA) in aqueous systems and soil slurries
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DOI：
10.1080/713610970
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发表时间：
2003-01-01
影响因子：
2
通讯作者：
Sperry, KL
中科院分区：
文献类型：
--
作者：
Liang, CJ;Bruell, CJ;Sperry, KL
在热激活条件下（即温度为 40 至 99 摄氏度），有大量证据表明过硫酸根阴离子 (S2O82-) 可以转化为强大的氧化剂，称为硫酸盐自由基 (SO4-)，可用于原位破坏地下水污染物。在本实验室研究中，20°C 时仅观察到有限的三氯乙烯 (TCE) 降解，未观察到 1,1,1-三氯乙烷 (TCA) 降解。然而，由于热激活的过硫酸盐氧化，TCE和TCA在40℃、50℃和60℃下很容易被氧化。实验表明，描述污染物降解的伪一级反应速率常数随着温度的升高而增加。在水性体系中，氧化剂/污染物摩尔比为 10/1 时，TCE 和 TCA 氧化的活化能分别在 pH 6 和离子强度 0.1 时测定为 97.74 +/- 3.04 KJ/摩尔和 163.86 +/- 1.38 KJ/摩尔。 TCE和TCA分别在40℃和50℃下在不到6小时内发生显着降解。水系统实验表明，过硫酸盐/污染物摩尔比增加时，氧化反应进行得更快。土壤泥浆测试是使用含有一定范围有机碳 (foc) 水平的中砂到细砂进行的。以 1/5 土壤/水（质量比）制备土壤浆液。在土壤泥浆中，焦点对产生的硫酸盐自由基表现出显着的竞争。基于这些结果，预计与水系统相比，有效处理土壤系统中的目标污染物需要更高的温度、更长的处理时间和更高的过硫酸盐剂量。
Under thermally activated conditions (i.e., temperature of 40 similar to 99degreesC), there is considerable evidence that the persulfate anion (S2O82-) can be converted to a powerful oxidant known as the sulfate free radical (SO4-.), which could be used in situ to destroy groundwater contaminants. In this laboratory study only limited trichloroethylene (TCE) degradation and no 1, 1, 1-trichloroethane (TCA) degradation was observed at 20degreesC. However, TCE and TCA were readily oxidized at 40degrees, 50degrees, and 60degreesC as a result of thermally activated persulfate oxidation. Experiments revealed that the pseudo-first-order reaction rate constants describing contaminant degradation increased with temperature. In aqueous systems activation energies for the TCE and TCA oxidation at an oxidant/contaminant molar ratio of 10/1 were determined to be 97.74 +/- 3.04 KJ/mole and 163.86 +/- 1.38 KJ/mole at pH 6 and an ionic strength of 0.1, respectively. A significant degradation of TCE and TCA occurs at 40degrees and 50degreesC, respectively, within less than 6 h. Aqueous system experiments revealed that oxidation reactions proceed more rapidly at increased persulfate/contaminant molar ratios. Soil slurry tests were conducted using medium to fine sands containing a range of fraction of organic carbon (foc) levels. Soil slurries were prepared at a 1/5 soil/water (mass ratio). In soil slurries the foc exhibited significant competition for sulfate free radicals produced. Based on these results, it was anticipated that higher temperatures, longer treatment times, and higher dosages of persulfate are required for the effective treatment of target contaminants in soil systems vs. aqueous systems.