Modeling of CO2 Adsorption Isotherms, Kinetics and Thermodynamics Equilibrium, and the Brunauer−Emmett−Teller Analysis onto KO2 Pellets

In this research, KO2 pellets as a solid adsorbent have been evaluated for the CO2 adsorption process. The KO2 pellets with advantages in CO2 uptake, besides O2 production, have been considered as air revitalization components, especially for closed respiratory environments in the infrastructure of life support systems (LSS). A unique set of experimental data of a single adsorption equilibrium of CO2 on KO2 pellet adsorbents at concentrations 8500–9500 mg L−1 (as closed atmosphere with a CO2% high value due to respiratory of human) and temperature 298.15 K is reported. Operating parameters such as temperature and humidity are tested experimentally to check the adsorption capacity. The maximum adsorption capacity at a temperature of 20 °C and humidity of 70% was 660 and 620 mg g−1, respectively. The kinetic study showed that the CO2 adsorption data correctly are adjusted by the Rate-controlling model with an R2 value of 0.984. The calculated thermodynamic parameters such as entropy (-0.0277 kJ mol−1 K−1), enthalpy (-12.406 kJ mol−1), and Gibbs free energy changes (-4.136 kJ mol−1) indicate the spontaneous and exothermic of the process. Equilibrium adsorption data were placed in the Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherms. Based on the regression coefficient (R2), the Dubinin-Radushkovich model provides a complete fit with the experimental data (R2 = 0.989). The BET-specific surface area of the KO2 pellets before and after the CO2 adsorption process was about 1.26 and 1.19 m2 g−1, respectively.