Cyclic CO2 capture behavior of slag-derived Li4SiO4: A kinetic analysis of CO2 desorption

Two slag-derived Li4SiO4 were synthesized using metallurgical slags as silica sources and used as CO2 sorbents. The CO2 desorption process was studied using a fixed temperature during the sorption step, with different CO2 partial pressures and several desorption temperatures. The kinetic parameters of the CO2 desorption were studied using the Avrami-Erofeev and zero-order models. With the latter, it was possible to calculate the activation energy of the desorption during the first minutes of the process, while with the Avrami-Erofeev model, only the energy associated with the second stage of the model was obtained. The calculated energies with the Avrami model were at least three orders of magnitude greater than the sorption stages reported values. Moreover, both models showed that the Li4SiO4 derived from the electric arc furnace (EAF) slag is less dependent on temperature than the derived from the blast furnace (BF). The kinetic parameters of desorption were also calculated for several regeneration cycles, where it was found that the k values diminish when lower partial pressures of CO2 (PCO2) were used. Finally, the structural evolution after the cyclic study showed the formation of secondary phases in the slag-derived silicates.