气态镉污染物的捕获与原位热固定效能与机理研究

Combustion process often produces gaseous cadmium compounds which pose substantial risks to the environment and public health. The conventional treatment techniques (e.g., sorbent injection and air pollution control technologies) have a number of drawbacks, including low efficient, the emission of metallic containing fine particles, the agglomeration of sorbents, the clogging of sorption sites and the need of additional ash stabilization. The development of a novel technology to economically and reliably eliminate gaseous cadmium compounds is urgently needed. Our previous results have demonstrated that cadmium oxide could react with Al/Fe-based oxides generating particular crystal structures, such as CdAl4O7 monoclinic structure and CdFe2O4 spinel, which possess a strong acid-resistant capability. However, a key challenge is how to effectively capture and in-situ thermal stabilize gaseous cadmium pollutants under extreme conditions. Therefore, in this study, multi-dimensional and nanoscale oxides with particular morphologies will be fabricated on the surface of a series of porous filters for in-line capture and in-situ thermal stabilization of cadmium. The scientific questions on capture behavior, stabilization mechanism and the effectiveness of capture and stabilization will be investigated in detail. The selection of filters and active oxide materials, self-assembly process and the quantification of incorporation efficiency are the key points of this study. These key points will be ruled out with the employment of quantitative XRD technique. The ultimate objective of this study is aiming to solve the migration problem of gaseous cadmium pollutants and provide a novel, effective and reliable method to clean gaseous metal pollutants from waste flue gas streams.

焚烧产生的烟气常含镉污染物，给环境和人类健康带来严重威胁。针对喷入粉末矿物吸附等方法存在效率低、不彻底、严重影响飞灰后续利用等不足，开发一种新的、经济的、有效的管内捕获耦合原位热固化技术极为迫切。镉与铝/铁基氧化物能发生固态反应，生成稳定的晶相化合物。然而，该类氧化物能否在高温及快气流的情况下，高效地捕获气态镉及对其进行即时的原位固化，是非常关键而又极具挑战的科学问题。对此，本课题尝试在滤块表面组装出多维度、高活性的氧化物材料，对气态镉进行管内捕获及原位热固定。本研究的创新点是低能耗的原位热固化。关键突破点在于对活性氧化物与烟气中镉的相互作用机制进行全面系统的研究。本项目将重点探讨活性氧化物的自组装过程、气态镉的捕获行为及原位热固化机制等科学问题。基于XRD定量技术，突破热固定效率难量化的瓶颈。最终解决烟气中镉污染物的环境迁移问题，为净化烟气中重金属污染物提供新的技术和理论。

为控制镉污染的环境问题，本研究在含镉污染物的热固化方面进行了深入的研究，具体地：（1）进行了用于镉污染物稳定化的活性氧化物材料的筛选、优化、评估及稳定化后产物的风险评估，得出富铁等前驱体对含镉污染物有高效的稳定化效果。（2）进行了活性氧化物材料在多孔陶瓷滤块表面的自组装及表征的研究，开展了应用常用氧化铁、石英、高岭土、莫来石、赤泥处理典型含镉污染物的研究。X射线衍射（XRD）及同步辐射近边精细结构分析（EXAFS）结果表明了镉铁尖晶石物相能有效固化镉。恒定pH值浸出实验（CPLT）表明该镉铁尖晶石物相物相具有良好的耐酸性能，能大大减少了镉铁尖晶石物相中镉的溶出，实现了镉的稳定化处理。该研究结果表明典型的铁基氧化物能很好地固定化镉污染物，合理地设计铁基氧化物能应用于镉污染物的捕获和稳定化。该部分的相关成果部分已发表在环境领域顶级期刊Environ. Sci. Technol.上。（3）探讨了硅氧化物，如无定型和晶型的二氧化硅，与镉污染物发生的晶相反应，生成镉硅酸盐晶相物质，这些物相大部分具有较好的耐酸性能，但其耐酸性与镉铁尖晶石物相相比仍有一定的差距，该部分成果发表在Environ. Pollut.。（4）高岭土、莫来石、赤泥等陶瓷前驱体能成功固化镉及其他有毒有害金属，生成耐酸性强的晶体物相，有效实现重金属污染物的去毒化，相关成果部分已发表在环境领域著名期刊Waste Manage.、Environ. Pollut.等上。（5）就镉稳定化及铁基功能材料的开发以及金属溶出实验等相关研究，本课题成员发表了SCI论文10余篇，申请了相关的发明和实用新型专利13余件（其中2件已授权），参与编写3本英文著作中的3个章节，参加了5次国际学术会议并作学术报告进行经验交流。总的来说，本研究进行的含镉污染物固化研究，实现了含镉污染物的固定化，取得了一定的成效。