Influence of ultra-micropore volume of activated carbons prepared from noble mung bean on the adsorption properties of CO2, CH4, and N2

Abstract

In this study, mung bean-based nanoporous activated carbons with different pore properties were prepared by varying the mass ratio of activating agent (KOH) and activation temperature. The low-temperature nitrogen adsorption analysis was used to characterize the effect of the KOH ratios and the activation temperatures on the textural properties and surface heterogeneity. The prepared ACs were further used to measure the adsorption capacity of CO₂, CH₄, and N₂. We found that the adsorption amounts were highly dependent on the ultra-micropore volume (V_D<0.8nm) rather than the surface area. Their adsorption characteristics were well explained by the polarizability and the adsorption energy distribution. The experimental adsorption isotherm data were well fitted to the Sips equation. The ideal adsorbed solution theory (IAST) was further applied to predict the adsorption selectivity of binary mixtures CO₂/N₂, CO₂/CH₄, and CH₄/N₂ at 25 °C.