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Atmospheric and Oceanic Optics

2017 year, number 12

Sorption of atmospheric gases (N2, O2, Ar, CO2, and H2O) by silica aerogel

B.A. Tikhomirov
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, 1, Academician Zuev square, Tomsk, 634021, Russia
Keywords: кремниевый аэрогель, атмосферный газ, адсорбция и десорбция, silica aerogel, atmospheric gases, adsorption and desorption


Adsorption and desorption of atmospheric gases (N2, O2, Ar, CO2, and H2O) in silica aerogel is studied. Static parameters of adsorption and kinetic parameters of adsorption and desorption are determined based on pressure vs time dependence P(t) in the buffer vacuum chamber of the experimental setup during adsorption and desorption of gases by a SiO2 aerogel sample of V = 42.8 cm3 in volume and ρ = 0.34 g/cm3 in density. The ratios of adsorbate molecular density to aerogel molecular density at the room temperature T = 293 K and equilibrium pressure Pр ≈ 1 bar are found: γ(N2) = (9 +- 3)% (9 molecules of N2 adsorbed by pore surface to 100 N2 molecules in the gas at equilibrium), γ(O2) = (7 +- 3)%, and γ(CO2) = (222 +- 8)%; for water vapour, γ(H2O) = (5.9 +- 0.3) x 104% at the pressure Pр = 5.7 mbar. It is ascertained that argon atoms are not adsorbed by the aerogel. It is suggested to use argon as a “zero” gas in spectroscopy of molecules adsorbed by SiO2 aerogel to determine the amount of adsorbate in a sample. A sum of two exponents with kinetic parameters τ1 and τ2 is used to fit P(t) dependence. The τ1 and τ2 values are estimated during adsorption and desorption of each gas under study.