Hydration Activation of MgO Pellets for CO2 Adsorption

Abstract

Mesoporous MgO is a promising candidate for CO₂ capture. In this study, MgO pellets were activated via hydration and the effects of the process on the texture, structures, and CO₂ adsorption properties of the pelletized MgO adsorbents were systematically studied. Two adsorption kinetics models were used to investigate the CO₂ adsorption kinetics of the pelletized MgO adsorbents. Simultaneously, their kinetic parameters and the influence of adsorption temperatures were determined. It was found that a 3D, flaky, inter-connected network structure appeared after hydration. The hydration process significantly improved the pore structure of the adsorbent and thereby improved the CO₂ adsorption capacity and equilibrium rate constant. The increase in CO₂ adsorption capacity was attributed to the development of their structure rather than the reaction of Mg(OH)₂ with CO₂. The results of a kinetics study showed that a pseudo-second-order model was suitable for predicting the entire adsorption process. Meanwhile, the equilibrium kinetics rate constant of CO₂ capture increased with adsorption temperature, but the initial adsorption rate was mainly related to the texture and structures of the adsorbents. Consequently, hydration by steam or liquid water was deemed an effective method for improving the adsorption performance of MgO pellets, and the hydrated adsorbents were suitable for use in practical CO₂ capture.