Zhao Xi, Kong Lingdong, Sun Zhenyu, Ding Xiaoxiao, Cheng Tiantao, Yang Xin, Chen Jianmin
J Phys Chem A. 2015 Apr 30;119(17):4001-8. doi: 10.1021/acs.jpca.5b01359. Epub 2015 Apr 16.
Sulfur dioxide and organic aldehydes in the atmosphere are ubiquitous and often correlated with mineral dust aerosols. Heterogeneous uptake and adsorption of one of these species on mineral aerosols can potentially change the properties of the particles and further affect the subsequent heterogeneous reactions of the other species on the coating particles. In this study, the interactions between heterogeneous uptake and adsorption of sulfur dioxide and acetaldehyde on hematite are investigated by using in situ diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS) at room temperature. It is found that the preadsorption of SO2 on α-Fe2O3 can significantly hinder the subsequent heterogeneous oxidation of CH3CHO to acetate, while the preadsorption of CH3CHO significantly suppresses the heterogeneous reaction of large amounts of SO2 on the surface of α-Fe2O3 and has a little influence on the uptake of small amount of SO2. The heterogeneous reactions of SO2 on α-Fe2O3 preadsorbed by CH3CHO change the existing acetate on the particle surface into chemisorbed acetic acid, for the enhancement of surface acidity after the uptake of SO2. During these processes, different surface hydroxyl groups showed different reactivities. Atmospheric implications of this study are discussed.
大气中的二氧化硫和有机醛类物质广泛存在，且常常与矿物粉尘气溶胶相关联。这些物质中的某一种在矿物气溶胶上的非均相吸收和吸附，可能会改变颗粒物的性质，并进一步影响另一种物质在包覆颗粒上随后发生的非均相反应。在本研究中，通过在室温下使用原位漫反射红外傅里叶变换光谱（DRIFTS），研究了二氧化硫和乙醛在赤铁矿上的非均相吸收与吸附之间的相互作用。研究发现，SO₂在α-Fe₂O₃上的预吸附能够显著阻碍随后CH₃CHO向乙酸盐的非均相氧化反应，而CH₃CHO的预吸附则显著抑制了大量SO₂在α-Fe₂O₃表面的非均相反应，并且对少量SO₂的吸收影响较小。SO₂在被CH₃CHO预吸附的α-Fe₂O₃上的非均相反应，将颗粒表面现有的乙酸盐转变为化学吸附的乙酸，这是由于SO₂吸收后表面酸度增强所致。在这些过程中，不同的表面羟基表现出不同的反应活性。本文还讨论了该研究对大气的影响。
