CO2capture properties of Li4SiO4after aging in air at room temperature

Abstract

In this study, we evaluated the physicochemical stability of lithium orthosilicate (Li4SiO4) powders after aging in air. Thermogravimetric (TG) analysis in CO2flow evidences that as-milled Li4SiO4stored in a closed plastic container in air at Room Temperature (RT) suffers a time progressive CO2absorption. This carbonation is clearly noticed in the samples with greater specific surface area and depends on two factors: the time of air exposure and the renewal of the air atmosphere in the plastic container, both of them modifying the CO2capture capacity and kinetics of the material. Specific experiments to analyze the effect of water vapor and carbon dioxide atmospheres on the CO2capture properties of Li4SiO4were designed. TG, X-ray diffraction and spectroscopic studies demonstrate that the reaction between as-milled Li4SiO4and CO2present in air was promoted by exposure to humidity. In fact, LiOH and LiOH.H2O were formed at the surface of Li4SiO4during water vapor exposure. These phases enhance the reaction with CO2from the air to form Li2CO3at RT before the first carbonation cycle. As a consequence, the CO2capture capacity of Li4SiO4in the first carbonation cycle was smaller than the one of Li4SiO4without water vapor exposure. In opposition, negligible CO2absorption occurred at RT under CO2atmosphere. The original properties of Li4SiO4powders with high specific surface area could be regenerated by heating at 700»°C. Consequently, the storage conditions of Li4SiO4powders should be considered for their use in different applications.