Adsorption equilibria and kinetics of NO and N2O on natural erionite exchanged with Fe, Co, and Cu

Abstract The present study investigated the equilibrium and kinetics of nitric oxide (NO) and nitrous oxide (N 2 O) adsorption at different temperatures on natural erionite from Agua Prieta, Sonora, Mexico (ZAPS), modified by ion exchange with Fe 2+ , Co 2+ , and Cu 2+ . UV–Vis diffuse reflectance, energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and Mössbauer spectroscopy were used to characterize the exchanged samples. The Freundlich, Langmuir, and Brunauer–Emmett–Teller (BET) models were employed to analyze the adsorption data. The isotherms of N 2 O and NO adsorption in the exchanged samples at the same temperature and at low equilibrium pressures showed that the adsorbed amount and irreversibility grade decrease in the order: ZAPS-Co > ZAPS-Fe > ZAPS-Cu, which was attributed to the increasing acidity of the cations. At high equilibrium pressures, the NO adsorption capacity changed in order due to the increased pore volume resulting from the exchange of smaller cations. At equilibrium, the ZAPS-Fe and ZAPS-Cu samples exhibited the best performance for separating NO/N 2 O mixtures at high temperatures and low concentrations, whereas for high concentrations, the ZAPS-Cu sample was the most effective for separation This result indicated that upon contact with the ZAPS-Cu catalyst, the NO/N 2 O mixture undergoes selective adsorption of NO, resulting in an increase in the relative concentration of N 2 O in the gas phase. Under non-equilibrium conditions at low temperatures, for the separation of N 2 O-NO mixtures, the N 2 O was adsorbed more rapidly than NO.