The influence of phenanthrene on the adsorption and conversion of SO2 on the hydroxylated {001} surface of α-quartz: A DFT study

One of the major challenges in environmental and atmospheric science is understanding the effects of mineral dust's surface physiochemical properties and pre-adsorbed volatile organic compounds on the conversion of atmospheric pollutants. However, the process of adsorption and conversion of polluting gases on typical mineral dust surface is not fully understood. In this study, we systematically investigated the impact of surficial hydroxyl groups on the α-quartz {001} surface, oxidizers, and adsorbed phenanthrene (Phe) on the adsorption and oxidation process of SO2 by using density functional theory. Our findings indicate that the presence of hydroxyl groups on the α-quartz {001} surface increases SO2 adsorption whereas the presence of Phe decreases the SO2 capture capabilities. On pristine α-quartz {001} surfaces, SO2 tends to form dissociative SO42- groups and adsorb SO3. While surficial hydroxylation of α-quartz {001} facilitates the desorption of SO3, resulting in fewer dissociative SO42- groups and HSO3- salt. These results are consistent with our heterogeneous reaction of SO2 and α-quartz. In addition, O3 is more effective than O2 in the oxidation of SO2. Meanwhile, Phe inhibits the adsorption of HSO3- salt on hydroxylated α-quartz {001} surfaces. This study not only highlights the process surficial hydroxyl groups and adsorbed Phe regulate the evolution of adsorbed SO2 on α-quartz {001}, but also revealed the formation mechanism of the sulfur-containing aerosols.