Influence of pH on persulfate oxidation of TCE at ambient temperatures
Influence of pH on persulfate oxidation of TCE at ambient temperatures
复制标题
DOI：
10.1016/j.chemosphere.2006.05.026
复制
发表时间：
2007-01-01
期刊：
影响因子：
8.8
通讯作者：
Bruell, Clifford J.
中科院分区：
文献类型：
--
作者：
Liang, Chenju;Wang, Zih-Sin;Bruell, Clifford J.
原位化学氧化是一种地下水修复技术。本实验室研究了在接近环境温度（10、20和30 ℃）下使用氧化剂过硫酸钠进行三氯乙烯（TCE）的化学氧化，以确定pH（pH = 4、7和9）对反应速率的影响（即，伪一级速率常数）。在磷酸盐缓冲的RO水中制备TCE溶液（60 mg/l（-1）; 0.46 mM），并且在所有测试中采用50/1的固定过硫酸盐/TCE摩尔比。三氯乙烯在10、20和30摄氏度（pH 7）下降解的半衰期分别为115.5、35.0和5.5小时。最大TCE降解发生在pH 7。降低系统pH值导致TCE降解速率的下降幅度大于增加系统pH值。用于确定主要自由基种类的自由基清除试验表明，硫酸根自由基（SO 4.-）在酸性条件下占优势，羟基自由基（（OH）-O-.）在基本条件下占主导地位。在地下水与未缓冲的RO水中TCE降解的并排比较中，证明了当系统pH由于天然存在的地下水成分的存在而缓冲至接近中性pH条件时，TCE降解速率高于未缓冲的RO水中，其中系统pH从5.9下降至2.8。这项研究的结果表明，在现场应用ISCO，pH值应进行监测，并调整到近中性，如果必要的。(c)2006爱思唯尔有限公司保留所有权利。
In situ chemical oxidation (ISCO) is a technology used for groundwater remediation. This laboratory study investigated the use of the oxidant sodium persulfate for the chemical oxidation of trichloroethylene (TCE) at near ambient temperatures (10, 20 and 30 C) to determine the influence of pH (pH = 4, 7 and 9) on the reaction rate (i.e., pseudo-first-order rate constants) over the range of temperatures utilized. TCE solutions (60 mg l(-1); 0.46 mM) were prepared in phosphate buffered RO water and a fixed persulfate/TCE molar ratio of 50/1 was employed in all tests. Half-lives of TCE degradation at 10, 20 and 30 degrees C (pH 7) were 115.5, 35.0 and 5.5 h, respectively. Maximum TCE degradation occurred at pH 7. Lowering system pH resulted in a greater decrease in TCE degradation rates than increasing system pH. Radical scavenging tests used to identify predominant radical species suggested that the sulfate radical (SO4.-) predominates under acidic conditions and the hydroxyl radical ((OH)-O-.) predominates under basic conditions. In a side by side comparison of TCE degradation in a groundwater vs. unbuffered RO water it was demonstrated that when the system pH is buffered to near neutral pH conditions due to the presence of natural occurring groundwater constituents that the TCE degradation rate is higher than in unbuffered RO water where the system pH dropped from 5.9 to 2.8. The results of this study suggest that in a field application of ISCO, pH should be monitored and adjusted to near neutral if necessary. (c) 2006 Elsevier Ltd. All rights reserved.