Heterogeneous Interaction of Isopropanol with Natural Gobi Dust

Abstract

The adsorption of isopropanol on Gobi dust was investigated in the temperature (T) and relative humidity (RH) ranges of 273-348 K and <0.01-70%, respectively, using zero air as bath gas. The kinetic measurements were performed using a novel experimental setup combining Fourier-Transform InfraRed spectroscopy (FTIR) and selected-ion flow-tube mass spectrometry (SIFT-MS) for gas-phase monitoring. The initial uptake coefficient, γ, of isopropanol was measured as a function of several parameters (concentration, temperature, relative humidity, dust mass). γ was found independent of temperature while it was inversely dependent on relative humidity according to the empirical expression: γ = 5.37 × 10/(0.77+RH). Furthermore, the adsorption isotherms of isopropanol were determined and the results were simulated with the Langmuir adsorption model to obtain the partitioning constant, K, as a function of temperature and relative humidity according to the expressions: K = (1.1 ± 0.3) × 10 exp [(1764 ± 132)/T] and K = 15.75/(3.21+RH). Beside the kinetics, a detailed product study was conducted under UV irradiation conditions (350-420 nm) in a photochemical reactor. Acetone, formaldehyde, acetic acid, acetaldehyde, carbon dioxide, and water were identified as gas-phase products. Besides, the surface products were extracted and analyzed employing HPLC; Hydroxyacetone, formaldehyde, acetaldehyde, acetone, and methylglyoxal were identified as surface products while the formation of several other compounds were observed but were not identified. Moreover, the photoactivation of the surface was verified employing diffuse reflectance infrared fourier transform spectroscopy (DRIFTs).

Uptake and surface chemistry of SO2 on natural volcanic dusts

“…Transported dust can also have a different composition further away from the source. Globally, when compared to other types of mineral dusts, such as Saharan dusts or Gobi dust (Joshi et al, 2017), the amount of silicon in all five v-dust samples is considerably lower while the amount of iron, magnesium, and titanium is higher (Romanias et al, 2016), (Langmann, 2013).…”

“…More information about influence of humidity on the steady state uptake of SO 2 on the surface of volcanic glass and ash is necessary to obtain a more comprehensive picture. While the increase in the SO 2 uptake with the increase of relative humidity is observed for a number of samples, it is not at all the case for the uptakes of other species, such as nonpolar volatile organic compounds (Romanias et al, 2016), hydrogen peroxide (H 2 O 2 ) (Romanias et al, 2012) or ozone (O 3 ) (Lasne et al, 2018). In fact, the uptake coefficient can decrease with increased humidity, such as the case for the steady state uptake of O 3 on montmorillonite clay dust reflecting the tendency for the molecules in question and molecules of water to compete with each other for the sorptive sites on the clay surface (Lasne et al, 2018).…”

Hygroscopic Properties of Saline Mineral Dust From Different Regions in China: Geographical Variations, Compositional Dependence, and Atmospheric Implications

“…It scatters and absorbs solar and terrestrial radiation (Balkanski et al, 2007;Chen et al, 2017;Di Biagio et al, 2017;Huang et al, 2015), and affects the formation and properties of clouds as well as precipitation via serving as cloud condensation nuclei (CCN; Karydis et al, 2017;Kumar et al, 2011;Tang et al, 2016) and ice-nucleating particles (Creamean et al, 2013;Cziczo et al, 2013;Murray et al, 2012;Tang et al, 2016). Heterogeneous reactions of mineral dust aerosol would significantly change the abundance of reactive trace gases in the troposphere and also contribute to the formation of secondary particulate matters, such as nitrate and sulfate (Dupart et al, 2012;He et al, 2014;Li & Shao, 2009;Romanias et al, 2016;Tang et al, 2017;Usher et al, 2003;Wang et al, 2013;Zhang & Iwasaka, 1999). Furthermore, deposition of mineral dust is known to be an important source of Fe and P in open oceans, largely controlling biogeochemical cycles in these regions (Conway & John, 2014;Jickells et al, 2005;Li et al, 2017;Mahowald et al, 2011;Mahowald et al, 2018).…”

Geocatalytic Uptake of Ozone onto Natural Mineral Dust

“…The BET surface of the sample, measured by a sorption analyzer using nitrogen as adsorbate gas, is 10.5 ± 2.0 m 2 g −1 . The relative abundances of mineral oxide phases in Gobi dust determined by XRD spectroscopy combined with ICP mass spectrometry are 55.0% SiO 2 , 17.8% CaCO 3 , 10.5% NaAlSi 3 O 8 , 6.9% Al 2 O 3 , 2.6% Fe 3 O 4 , 1% TiO 2 and 6.2% of uncounted fraction [36].…”

“…This experimental set up has been used extensively in the past to investigate the heterogeneous interaction/reaction of volatile organic compounds (VOCs) and inorganic species with natural mineral dusts and proxies [36][37][38][39][40], and thus only a brief description is provided. relative abundances of mineral oxide phases in Gobi dust determined by XRD spectroscopy combined with ICP mass spectrometry are 55.0% SiO2, 17.8% CaCO3, 10.5% NaAlSi3O8, 6.9% Al2O3, 2.6% Fe3O4, 1% TiO2 and 6.2% of uncounted fraction [36].…”