Thermal behavior and CO2 absorption of Li2-xNaxZrO3 solid solutions

Lithium-sodium metazirconate solid solutions, Li2-xNaxZrO3, were tested as CO2 captors. The thermal analyses of these materials showed that all the solid solutions present similar behaviors under air and N-2. The samples lost weight due to two different processes, desorption of physisorbed water (similar to 100 degrees C) and a decarbonation process (400-700 degrees C). In fact, the quantities of water and CO2 desorbed increased as a function of the sodium content. Thermal analyses into a CO2 flux showed that Li2-xNaxZr2O7 solid solutions present a high CO2 absorption. The solid solutions absorb CO2 between 400 and 600 degrees C, but samples containing the sodium phase absorbed CO2 in two distinct steps. First, at low temperatures, there is a CO2 chemisorption, only at the surface of the particles, forming a carbonate shell. Later, when the temperature reaches 400 degrees C, or more, a second absorption process takes place. In this process lithium and/or sodium atoms diffuse from the core of the particles to the surface, through an external carbonate shell. The differences observed in the CO2 sorption processes were explained with thermodynamic data.