Home – Home – Jornals – Atmospheric and Oceanic Optics 2017 number 12

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 P_р ≈ 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 P_р = 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.