Yu Shenghui, Zhang Cheng, Ma Lun, Fang Qingyan, Chen Gang
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
J Hazard Mater. 2021 Apr 5;407:124742. doi: 10.1016/j.jhazmat.2020.124742. Epub 2020 Dec 9.
Mineral oxides are effective in-furnace sorbents used to control lead (Pb) emissions in flue gas at high temperatures. In this paper, the PbO/PbCl adsorption characteristics of sorbents were investigated via experimental and density functional theory (DFT) methods. The results show that Si/Al-based compounds can chemically adsorb Pb, and the adsorption is related to the Si-O and Al-O bonds in the sorbents. Exposed Si and O atoms on SiO surfaces and exposed Al and O atoms on AlO surfaces are the active sites for Pb adsorption, and PbO is easier to remove than PbCl. Pb adsorption is promoted in a mixture of SiO and AlO. Doping Si atoms into AlO(100) promotes PbO adsorption, and doped three-coordinate Si atoms have a more obvious promotion effect than doped two-coordinate Si atoms. Doping Al atoms into SiO(001) has no obvious effect on PbO adsorption. The effect of temperature on Pb adsorption was studied by thermodynamic analysis. The Gibbs free energy difference for PbO adsorption on SiO(001) increases from -373.04-32.42 kJ/mol as the temperature increases from 300 to 1800 K. High-temperature calcination changes the bond length and bond angle of the system, affecting the stabilities of atomic configurations and decreasing the Pb adsorption capacity.
金属氧化物是用于控制高温烟道气中铅（Pb）排放的高效炉内吸附剂。本文通过实验和密度泛函理论（DFT）方法研究了吸附剂对PbO/PbCl的吸附特性。结果表明，硅铝基化合物能够化学吸附铅，且吸附作用与吸附剂中的Si-O键和Al-O键有关。SiO表面暴露的Si和O原子以及AlO表面暴露的Al和O原子是铅吸附的活性位点，且PbO比PbCl更容易去除。在SiO和AlO的混合物中，铅的吸附作用增强。将Si原子掺杂到AlO(100)中可促进PbO的吸附，且掺杂的三配位Si原子比二配位Si原子具有更明显的促进作用。将Al原子掺杂到SiO(001)中对PbO的吸附没有明显影响。通过热力学分析研究了温度对铅吸附的影响。随着温度从300 K升高到1800 K，PbO在SiO(001)上吸附的吉布斯自由能差从-373.04变为-32.42 kJ/mol。高温煅烧改变了体系的键长和键角，影响了原子构型的稳定性并降低了铅的吸附能力。
