Study On Adsorption And Dynamic Transformation Mechanism Of Sulfur Dioxide On Common Mineral Dust Surface

The high concentration of atmospheric particulate matter seriously affects the air quality of Our country.Secondary particulate matter occupies the main part of atmospheric particulate matter,and the secondary transformation of harmful gases is the main cause of the formation of secondary particulate matter.The secondary conversion of sulfur dioxide to sulfate is the most important in the formation of secondary particulate matter,because when gas sulfuric acid molecules collide with dimethylamine randomly,molecular clusters can be formed through hydrogen bonds.When the molecular cluster collides with sulfuric acid or dimethylamine,it can continue to grow,so as to form the network structure of sulfuric acid dimethylamine,so as to strengthen the adhesion ability of haze particles to minerals and organic matter.Sulfur dioxide itself is difficult to be directly oxidized,and the second transformation process usually occurs on the surface of atmospheric dust,which is mainly composed of mineral dust.Therefore,it is very important to study the catalytic oxidation of SO₂ on the surface of mineral dust to study the formation process of haze.In this paper,the catalytic oxidation process of SO₂ on the surface of common mineral dust was studied by first-principles calculation.The main research work is as follows:（1）The main components of mineral dust in atmospheric particulate matter in China were investigated.Surface by calculation to get the main mine dust in the atmosphere is most likely exposed section,calculating the break in the face of SO₂ adsorption can draw the different mineral adsorption capacity of SO₂,and through charge density difference,the density of states,crystal Hamiltonian orbital overlap integral layout and element valence charge different minerals and the interaction mechanism of SO₂ was studied.In addition,the effect of different defects on the surface of calcite on SO₂ adsorption was also studied.The results show that the highest adsorption strength of SO₂ is albite,followed by Muscovite and calcite,and the element doping can effectively improve the adsorption strength of SO₂ by calcite.（2）The catalytic capacity of different mineral dust to oxidize SO₂ by O₂ or O₃ in the E-R reaction mode was studied.The results of reaction path calculation show that the oxidation reaction of SO₂ and O₃ is the most likely to occur on the surface of albite,followed by Muscovite and calcite.O₂ has a hard time oxidizing SO₂ on the dust surface.Muscovite adsorbs SO₂ on the surface and then generates O₂ and sulfur trioxide with O₃,while albite and calcite form adsorbed oxygen and O₂ on the dust surface through O₃ first,and adsorbed oxygen reacts with sulfur dioxide to generate sulfur trioxide.In this process,only Muscovite easily generates gaseous sulfur trioxide,while both calcite and albite tend to surface sulfurize rather than release gaseous sulfur trioxide.（3）The surface hydration process of different mineral dust was studied.The transition state calculation shows that water dissociation cannot occur on the pure calcite surface,but water dissociation easily occurs on the carbonate vacancy calcite,followed by weak water dissociation on the doped defect calcite surface.Water cannot dissociate on the surface of Muscovite,but albite can directly decompose water into hydroxyl radicals leading to surface hydration.We also studied the catalytic oxidation capacity of each mineral dust to SO₂ after hydration.The calculation of reaction path shows that the surface hydration of calcite strengthens the oxidation capacity of SO₂,but the surface hydration of albite prevents the dynamic transformation process of SO₂ above it.In a word,all three kinds of mineral dust can accelerate the conversion of SO₂ to sulfate,but the increase of humidity is only conducive to the oxidation of SO₂ on calcite and not conducive to the oxidation of SO₂ on albite.