LAUSR

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 the pressure vs time dependence P(t) in the buffer vacuum chamber of an experimental setup during adsorption and desorption of gases in a SiO2 aerogel sample 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 room temperature T = 293 K and equilibrium pressure Pe ≈ 1 bar are found: γ(N2) = (9 ± 3)% (nine N2 molecules adsorbed by pore surface to 100 N2 molecules in the gas at equilibrium), γ(O2) = (7 ± 3)%, and γ(CO2) = (222 ± 8)%; for water vapor, γ(H2O) = (5.9 ± 0.3) × 104% at Pe = 5.7 mbar. It is ascertained that Ar 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 exponential functions of kinetic parameters τ1 and τ2 is used to fit the P(t) dependence, where τ1 and τ2 values are estimated during the adsorption and desorption of each gas under study.