Modeling of CO2 Adsorption on Surface-Functionalized Rubber-Seed Shell Activated Carbon: Isotherm and Kinetic Analysis

Abstract

Currently, adsorption is considered a promising technology for CO2 separation with a wide range of adsorbents. A detailed study of equilibrium and kinetics plays a crucial role in the design and operation of industrial adsorption units. In this study, isotherm and kinetics of CO2 adsorption on two RSS-derived AC samples previously prepared in our laboratory were evaluated using equilibrium experiments for pure CO2 at 25 °C and 40 °C and 1 bar. Blank and IL-functionalized AC showed CO2 adsorption capacity of 2.16 mmol/g, 1.96 mmol/g, 1.12 mmol/g and 1.71 mmol/g at 25 °C and 40 °C, respectively. Langmuir, Freundlich, and Temkin equations were used to model adsorption isotherm in low-pressure regions. The obtained results revealed that the Freundlich model provides an accurate fitting to the experimental findings, which indicate that the adsorption process occurs in a heterogeneous phase. Additionally, kinetic analysis was performed by using four empirical models, namely pseudo-first order, pseudo-second order, Elovich, and Avrami’s fractional models. Among the considered kinetic models, the pseudo-second order model fits best for both blank and IL-functionalized AC. Intra-particle and Boyd’s film diffusion models were evaluated for the adsorption mechanism.