Synthesis and Performance of Zr(OH)_n(CO₃)_m–ZnO Composite Adsorbent for CO₂ Capture and Concentration from Air in Closed Environments

The features of the formation of the porous structure of a \(\mathrm{Zr(OH)_n(CO_3)_m}\)--\(\mathrm{ZnO}\) composite adsorbent, as well as its thermal and sorption properties with respect to \(\mathrm{CO_2}\), have been studied in relation to the life-support systems for closed environments. It has been established that the amorphous micro-mesoporous structure of the material is formed during the synthesis of the adsorbent at the hydrothermal treatment stage as a result of the hydrolysis of zirconium hydrocarbonate. The specific surface area and micropore volume of the material increase almost a hundredfold compared with the initial zirconium hydrocarbonate and amount to \(298~\mathrm{m^2/g}\) and \(0.120~\mathrm{cm^3/g}\), respectively. Zinc oxide acts as a stabilizing additive that mitigates the degradation of the porous structure of \(\mathrm{Zr(OH)_n(CO_3)_m}\) and of the adsorbent as a whole upon its contact with water vapor during operation, particularly during regeneration. The material exhibited a high sorption capacity for carbon dioxide under dynamic conditions (of the order of \(9\text{--}11.5~\mathrm{L/L}\) at a \(\mathrm{CO_2}\) content in the air mixture equal to \(0.4\text{--}1.0\%\)) and stability over long-term resource testing (4600 adsorption--desorption cycles), which makes it possible to recommend it for \(\mathrm{CO_2}\) capture and for the air revitalization of space complexes.