Graduate Institute of Environmental Engineering, National Central University, Chungli 320, Taiwan.
Sci Total Environ. 2013 Jan 15;443:590-6. doi: 10.1016/j.scitotenv.2012.11.014. Epub 2012 Dec 7.
This study investigates the behavior of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) formation, dechlorination and destruction in PCP-contaminated sandy soil by low-temperature thermal treatment. Experimental tests were carried out in a nitrogen atmosphere in the temperature range of 200-400 °C with a treatment time of 30 min. 70% of PCP removal from the soil was achieved, resulting in 1436±230 ng/kg, the highest PCDD/F formation at 250 °C; however, the highest toxic concentration was measured around 4.20±0.62 ng TEQ/kg at 300 °C with 80% PCP removal from the soil. Further analysis has revealed that OCDD is the most dominant congener that is supposed to be formed from the pyrolysis of PCP, while OCDF is the second prevailing congener, possibly due to pyrolysis of 2,3,4,5-TeCP being a main byproduct of PCP pyrolysis. Detection of less chlorinated dioxins and furans over 300 °C indicates the dechlorination of highly chlorinated dioxins and furans, especially octachlorinated dibenzo-p-dioxin (OCDD) at 350 °C and 400 °C. Desorption from soil was supposed as a main mechanism for the distribution of PCDD/Fs in the gaseous phase, and not much difference in dioxins and furan levels was observed at 350 °C and 400 °C in the gaseous phase. Therefore, 350 °C is the most appropriate temperature to remove most PCP and PCDD/Fs from soil, as well as to meet PCDD/F emission standards (0.1 ng I-TEQ/Nm(3)).
本研究调查了低温热疗法在受五氯酚污染的沙质土壤中多氯二苯并对二恶英和呋喃（PCDD/Fs）形成、脱氯和破坏的行为。在氮气气氛中，实验温度范围为 200-400°C，处理时间为 30 分钟。从土壤中去除了 70%的五氯酚，达到了 1436±230ng/kg，在 250°C 时形成了最高的 PCDD/F；然而，在 300°C 时，土壤中 80%的五氯酚去除后，测得的最高毒性浓度为 4.20±0.62ng TEQ/kg。进一步的分析表明， OCDD 是最主要的同系物，应该是由五氯酚的热解形成的，而 OCDF 是第二主要的同系物，可能是由于 2,3,4,5-TeCP 的热解是五氯酚热解的主要副产物。在 300°C 以上检测到较少的氯代二恶英和呋喃表明高度氯代二恶英和呋喃的脱氯，特别是在 350°C 和 400°C 时，八氯代二苯并对二恶英（OCDD）的脱氯。从土壤中的解吸被认为是 PCDD/F 在气相中分布的主要机制，在 350°C 和 400°C 时气相中观察到的二恶英和呋喃水平没有太大差异。因此，350°C 是从土壤中去除大部分五氯酚和 PCDD/F 以及达到 PCDD/F 排放标准（0.1ng I-TEQ/Nm³）的最适温度。
