Graduate Institute of Environmental Engineering, National Central University, Chungli 320, Taiwan.
Chemosphere. 2013 Aug;92(7):857-63. doi: 10.1016/j.chemosphere.2013.04.042. Epub 2013 May 25.
Removal and destruction of dioxin-like congeners, including polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs), from fly ash were investigated at varying pyrolysis temperatures and reaction times and using calcium-based additives. Destruction efficiencies based on TEQ and mass both increase with rising treatment temperature. However, additional low chlorinated PCDD/Fs were formed significantly by dechlorination of high chlorinated PCDD/Fs, at pyrolysis temperatures of 250 and 300°C. Surprisingly, lower destruction efficiencies were realized in the presence of Ca-based additive, compared with those without additive, and TEQ values of fly ash into which CaO was introduced increased, compared with the raw ash, due to significant formation of low chlorinated PCDD/Fs (4-5 Cl). However, complex interactions among unburned carbon, sulfur and metals in the fly ash collected in this study make it difficult to pinpoint the exact causes. The results obtained in this study indicate that degradation and formation of dioxin-like congeners take place simultaneously in pyrolysis process, such as formation of low chlorinated PCDD/Fs via dechlorination of highly chlorinated PCDD/Fs.
研究了在不同的热解温度和反应时间下，使用钙基添加剂从飞灰中去除和破坏二恶英类似同系物，包括多氯二苯并对二恶英（PCDDs）、二苯并呋喃（PCDFs）和多氯联苯（PCBs）。基于 TEQ 和质量的破坏效率都随着处理温度的升高而增加。然而，在 250 和 300°C 的热解温度下，高氯代 PCDD/Fs 的脱氯会显著形成额外的低氯代 PCDD/Fs。令人惊讶的是，与没有添加剂的情况相比，在存在钙基添加剂的情况下，破坏效率较低，并且由于低氯代 PCDD/Fs（4-5 Cl）的大量形成，引入 CaO 的飞灰的 TEQ 值会增加，与原始灰分相比。然而，在本研究中收集的飞灰中未燃烧的碳、硫和金属之间的复杂相互作用使得难以确定确切的原因。本研究的结果表明，在热解过程中二恶英类似同系物的降解和形成同时发生，例如通过高度氯化的 PCDD/Fs 的脱氯形成低氯化的 PCDD/Fs。
