Study on the mechanism of SeO2 adsorption by NaHCO3 based on experiment and density functional theory
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摘要: 本研究通过吸附实验探究了140−220 ℃下NaHCO3对SeO2的吸附性能,通过一系列表征解析了吸附后样品中硒的总量、价态和形态,结合密度泛函理论计算,探讨了NaHCO3对SeO2的吸附机理。结果表明,NaHCO3对SeO2的吸附性能随温度的升高而增加,在吸附过程中同时发生NaHCO3向Na2CO3的分解反应,分解后产生的Na2CO3吸附活性更强。SeO2吸附过程属于SeO2中Se原子与Na2CO3表面O原子成键的化学吸附,吸附产物以亚硒酸盐为主。Abstract: In this paper, the adsorption performance of NaHCO3 on SeO2 at 140−220 ℃ is investigated by adsorption experiments, and the total amount, valence and morphology of selenium in the adsorbed samples are resolved by series characterization, and the adsorption mechanism of NaHCO3 on SeO2 is discussed in depth by combining with density functional theory calculations. The results show that the adsorption performance of NaHCO3 on SeO2 increases with the increase of temperature, and the thermal decomposition reaction of NaHCO3 to Na2CO3 occurs simultaneously during the adsorption process, and the Na2CO3 produced after the thermal decomposition has stronger adsorption activity. The SeO2 adsorption process belongs to the chemical adsorption of Se atoms in SeO2 bonded to O atoms on the surface of Na2CO3, and the adsorption products are mainly selenite.
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Key words:
- NaHCO3 /
- SeO2 /
- density functional theory /
- chemical adsorption
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图 6 热分解前后NaHCO3的SEM照片
Figure 6 SEM images of NaHCO3 before and after thermal decomposition
(a): NaHCO3 at a magnification of 500 times; (b): NaHCO3 at a magnification of 5000 times; (c): Na2CO3 after thermal decomposition at a magnification of 500 times; (d): Na2CO3 after thermal decomposition at a magnification of 5000 times
表 1 比表面积及孔结构分析
Table 1 Specific surface area and pore analysis
Sample Specific surface
area /(m2·g−1)Aperture /nm Hole volume /(cm3·g−1) NaHCO3 0.183 15.6530 7.156×10−4 NaHCO3-140 1.667 13.7248 5.720×10−3 NaHCO3-180 3.331 13.0694 1.088×10−2 NaHCO3-220 3.831 10.2196 1.232×10−2 表 2 SeO2在Na2CO3(001)表面的吸附构型及吸附能
Table 2 Adsorption configuration of SeO2 on the surface of Na2CO3(001) and adsorption energy (Red: O; gray: C; purple: Na; orange: Se)
Placement Adsorption configuration Eads/ (kJ·mol−1) main view top view (a) Osurf top,horizontal −127.529 (b) Osurf top,vertical −113.218 (c) Vacancy,horizontal −109.455 (d) Vacancy,vertical −99.035 (e) Na top,horizontal −87.553 (f) Na top,vertical −90.834 -
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