Effects of potassium doping on the composition, structure and carbon dioxide chemisorption of Na$_{2}$ZrO$_{3}$

Abstract

Solid solutions of sodium and potassium metazirconate, Na$_{2 - x}$K$_{x}$ZrO$_{3}$, were prepared by coprecipitation. Then, samples were characterized by powder X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. Results show that the solubility limits of potassium in Na$_{2}$ZrO$_{3}$ is 0.2, Na$_{1.8}$K$_{0.2}$ZrO$_{3}$, and the addition of potassium produced the formation of needle-like particles. Furthermore, Na$_{2 - x}$K$_{x}$ZrO$_{3}$ solid solutions were tested as CO$_{2}$ captors. The analyses of these materials showed that, although all the solid solutions present similar behaviors, the chemisorption and diffusion kinetics were enhanced by the addition of potassium. Na$_{1.6}$K$_{0.4}$ZrO$_{3}$ seems to be the best solid solution for the CO$_{2}$ capture. The differences observed in the CO$_{2}$ sorption processes were explained by the different ionic radii of sodium and potassium and with thermodynamic data.