Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, China.
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, China.
Sci Total Environ. 2023 Feb 1;858(Pt 2):159895. doi: 10.1016/j.scitotenv.2022.159895. Epub 2022 Nov 3.
Si/Al-based adsorbents are effective adsorbents for capturing heavy metals in incineration flue gases at high temperatures in the furnace. In this work, the adsorption characteristics and adsorption mechanisms of Si/Al-based adsorbents for lead and cadmium vapors were studied using a combination of experimental and density functional theory (DFT) calculations. The trapping performance of a series of Si/Al-based adsorbents for Pb and Cd vapors was investigated using a self-designed gas-solid two-phase rapid adsorption experimental system. The results showed that kaolinite and montmorillonite exhibited better heavy metal adsorption capacity than SiO and AlO, and were significantly stronger for Pb than for Cd. Chemisorption dominated the capture of Pb/Cd by Si/Al-based adsorbents at high temperatures. The results of DFT calculations indicated that the chemisorption mechanisms dominated the adsorption of Pb and Cd species on the metakaolinite (001) surface, and the adsorption energy of Pb species on the metakaolinite surface was greater than that of Cd species. The exposed O atoms and unsaturated Al atoms of metakaolinite (001) surface were effective adsorption active sites for heavy metals and their chlorides. In the adsorption reaction, the binding of Pb/Cd atoms and surface exposed O sites, as well as the strong interaction between Cl and unsaturated Al atoms, were responsible for the capture of Pb and Cd chlorides by metakaolinite.
硅铝基吸附剂是一种有效的吸附剂，可在炉内高温下捕获焚烧炉烟气中的重金属。本工作采用实验与密度泛函理论（DFT）计算相结合的方法，研究了硅铝基吸附剂对铅和镉蒸气的吸附特性和吸附机理。采用自行设计的气固两相同速吸附实验系统，考察了一系列硅铝基吸附剂对 Pb 和 Cd 蒸气的捕集性能。结果表明，高岭石和蒙脱石对重金属的吸附能力优于 SiO 和 AlO，对 Pb 的吸附能力明显强于 Cd。高温下，硅铝基吸附剂对 Pb/Cd 的捕获以化学吸附为主。DFT 计算结果表明，Pb 和 Cd 物种在偏高岭石（001）表面的吸附以化学吸附机制为主，Pb 物种在偏高岭石表面的吸附能大于 Cd 物种。偏高岭石（001）表面暴露的 O 原子和不饱和 Al 原子是重金属及其氯化物的有效吸附活性位。在吸附反应中，Pb/Cd 原子与表面暴露的 O 位的结合以及 Cl 与不饱和 Al 原子的强相互作用，是偏高岭石捕获 Pb 和 Cd 氯化物的原因。
