Formation and Stability of a Porous Structure of Zr(OH)4-Based Adsorbent for CO2 Capture from the Atmospheres of Isolated Systems

The formation features of the porous structure of a Zr(OH)4–ZnO composite adsorbent and its sorption properties toward CO2 were investigated. It was found that the micro–mesoporous structure of the material is due to the presence of zirconium hydroxide, which forms during the adsorbent synthesis mainly in the hydrothermal treatment stage as a result of hydrolysis of zirconium hydroxycarbonate by water vapor. The specific surface area and micropore volume of the Zr(OH)4–ZnO adsorbent, granulated by extrusion, range from 279 to 322 m2/g and from 0.119 to 0.131 cm3/g, respectively, which is nearly two orders of magnitude greater than those parameters of the starting material. Zinc oxide acts as a stabilizing additive that prevents degradation of the porous structure of zirconium hydroxide and of the adsorbent as a whole upon contact with water vapor during synthesis and operation (during regeneration). The obtained material exhibited a high sorption capacity for carbon dioxide under dynamic conditions (about 7.5 L CO2 per liter of adsorbent) and stability over 4600 adsorption–desorption cycles, which makes it recommended for CO2 removal from the atmosphere of space systems.