Thermal Behavior and CO₂ Absorption of Li_2-xNa_xZrO₃ Solid Solutions

Lithium−sodium metazirconate solid solutions, Li 2- x Na x ZrO 3, were tested as CO 2 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 (∼100 °C) and a decarbonation process (400−700 °C). In fact, the quantities of water and CO 2 desorbed increased as a function of the sodium content. Thermal analyses into a CO 2 flux showed that Li 2- x Na x Zr 2 O 7 solid solutions present a high CO 2 absorption. The solid solutions absorb CO 2 between 400 and 600 °C, but samples containing the sodium phase absorbed CO 2 in two distinct steps. First, at low temperatures, there is a CO 2 chemisorption, only at the surface of the particles, forming a carbonate shell. Later, when the temperature reaches 400 °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 CO 2 sorption processes were explained with thermodynamic data.