热过程低氯代与高氯代二恶英的诱导氯化与脱氯脱毒机制研究

Dioxin emissions from the municipal solid waste incineration have caused public concern, as it could be interpreted as an environmental, social or political issue. The major object of this project is low chlorinated dioxins. By optimizing pre-treatment methods, we plan to establish and improve the analysis of low chlorinated dioxin in various environmental media. Through the measurement of the stack gas and ash samples from typical sources, we would investigate the profile of low chlorinated dioxins, and provide the basic information for the online detection of dioxins. The spatial distribution, migration and transformation of lower chlorinated dioxins would be studied in the surrounding environment of the sources. The model studies of de novo formation and precursor formation of lower chlorinated dioxins are expected, and transformation of low and high chlorinated dioxins under various conditions would be simulated. By adjusting the combustion conditions and controlling the degree of chlorination of dioxins, we would conduct mechanistic studies on the chlorination of low chlorinated dioxins and reductive dechlorination of high chlorinated dioxins. By exploring the key factors influencing the reaction mechanism, not only could we reduce the total amount of low and high chlorinated chlorinated dioxins, but also reduce the proportion of toxic congeners in dioxins. From these two aspects, dioxins emissions is expected to be cut down, thus providing a theoretical basis for the reduction of total emissions and toxic dioxins emissions.

生活垃圾焚烧二恶英排放问题是民众广泛关注的环境、社会和政治问题。以低氯代二恶英为研究核心，通过优化前处理方法等途径，建立和完善多环境介质低氯代二恶英分析方法。通过对典型排放源烟气和飞灰样品检测，开展低氯代二恶英排放特征研究，为实现二恶英在线检测提供基础信息。开展周边环境低氯代二恶英空间分布特征研究和迁移转化规律研究。开展低氯代二恶英de novo生成机制和前驱体生成机制研究，并模拟多种情景下低氯代与高氯代二恶英的生成与消减机制。通过调节反应气氛，调整体系中生成的二恶英的氯化度，开展低氯代诱导氯化生成高氯代二恶英的反应机制研究，以及高氯代脱氯生成低氯代二恶英的脱氯脱毒反应机制研究。探索影响反应机制的关键因素，期望研究结果从两方面消减二恶英的产生与排放，不仅可以减少低氯代和高氯代二恶英的总量，也能降低二恶英毒性同类物的占比，从而为二恶英总量减排和毒性减排提供理论基础。

利用低氯代二恶英类标准品建立有效的同位素稀释高分辨气相色谱质谱的测定方法，测定了10同类物包括了1-MoCDF、2-MoCDF、3-MoCDF、4-MoCDF、1-MoCDD、2-MoCDD、2,3-DiCDF、2,8-DiCDD、2,3,7-TriCDF和2,4,8-TriCDD。开展了城市生活垃圾焚烧厂和医疗废弃物焚烧厂的低氯代二噁英研究，发现2,8-DiCDF和2,4,8-TrCDF可能在在线监测中作为TEQ指示物。开展了再生有色金属冶炼过程中低氯代与高氯代二噁英的研究，发现10种被检测的低氯代二恶英同类物中，1-MoCDF和4-MoCDF的浓度最高，平均贡献率分别为25.58%和34.10%。此外还开展了所有二噁英同类物的研究，发现非2,3,7,8-PCDD/Fs普遍高于相应的2,3,7,8-PCDD/Fs同类物的浓度，非2,3,7,8-PCDD/Fs更倾向于存在在气相烟道气中，从而不容易被布袋除尘器等污控设施有效去除，可能引起一定的环境和健康风险。通过量子力学计算发现，2-MCDF、2,8-DCDF、2,4,8-TrCDF和2,3,4,7,8-PCDF是关键的二噁英同类物。研究发现，低氯代二恶英类可以为二恶英类的生成机制研究提供有价值的信息，通过对1-8氯代二恶英类进行全分析，全面考察二恶英的浓度水平、分布特征，探索其生成机制，为二噁英的减排提供参考。研究过程中共发表SCI文章15篇，培养并毕业了3名硕士研究生，1名博士研究生，达到了项目的预期目标。..