Unary Adsorption Isotherm of Carbon Dioxide and Methane of Nickel Gallate Metal-organic Framework

Carbon dioxide (CO₂) and methane (CH₄) adsorption using metal-organic frameworks (MOFs) has garnered continuous interest in academia and industrial fields due to their remarkable performances. A series of studies have been dedicated to design the potential MOFs for CO₂ and CH₄ adsorption. Among them, nickel gallate MOF (Ni-gallate) can act as a promising adsorbent based on the predicted adsorption capacity and selectivity. However, the behaviors of CO₂ and CH₄ unary adsorption isotherms of Ni-gallate have not been studied by isotherm and kinetic models. Therefore, the aim of this work is to perform pure CO₂ and CH₄ gas adsorption and the unary adsorption isotherms were explained by the isotherm and kinetic models. Based on the unary adsorption isotherms, CO₂ adsorption capacity values were observed to be higher than CH₄ which resulted in great selectivity values. For isotherm models, the Toth model demonstrated the highest goodness-of-fit compared to Langmuir, Freundlich and Sips models and the thermodynamic properties were determined using its constant values. On the other hand, the kinetic data was best-fitted by the pseudo-first order model compared to the pseudo-second order and Elovich models and its constant values were used to determine activation energy. This useful information is very important for the design and operation of CO₂ and CH₄ adsorption systems.