Unique adsorption and desorption behaviour of ammonia gas at heating temperature using the Prussian blue analogue Zn3[Co(CN)6]2

• Published in: Inorganica Chimica Acta 2020-02, Vol.501, p.119273, Article 119273
• Main Authors: Jiang, Yong, Takahashi, Akira, Kawamoto, Tohru, Asai, Miyuki, Zhang, Nan, Lei, Zhongfang, Zhang, Zhenya, Kojima, Keisuke, Nakamura, Tohru
• Format: Article
• Language: English
• Subjects: Adsorption; Ammonia; Crystal structure; Desorption; Fourier transforms; Heating; Heating temperature; Infrared spectroscopy; Isotherms; Nanoparticles; Pigments; Room temperature; Stability analysis; Thermal stability; Thermogravimetric analysis; X ray powder diffraction; Zinc; Zinc hexacynanocobaltate
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2019.119273

Zinc hexacyanocobaltate (Zn3[CoIII(CN)6]2, abbreviation: ZnHCCo) was proved to have an exceptionally high thermal stability in adsorption–desorption cycles by pressure swing adsorption (PSA) and temperature swing adsorption (TSA) processes. [Display omitted] •High thermal stability of Prussian blue analogue ZnHCCo up to around 350 °C.•Unique adsorption/desorption isotherms, i.e., hysteresis curves of ZnHCCo.•Possibility of pressure and temperature swing processes for NH3 recovery. Nanoparticles (NPs) of Zinc hexacynanocobaltate (ZnHCCo) were synthesised and characterized by analytical measurements. Thermogravimetric analysis revealed great thermal stability of the ZnHCCo NPs up to ~350 °C, even under ambient air conditions including water and oxygen. Ammonia (NH3) adsorption isotherms revealed that the ZnHCCo NPs exhibited a great adsorption capacity at room temperature. This was maintained at the heating temperatures 100–250 °C, in which the isotherm displayed special hysteresis curves in the adsorption/desorption processes. Based on these results, the ZnHCCo NPs were applied to NH3 gas adsorption/desorption in pressure (PSA) and temperature (TSA) swing adsorption processes by using a gas cell of FTIR, to confirm that both processes are possible. Characterisation before/after NH3 exposure, by in-situ FTIR and X-ray powder diffraction (PXRD) spectroscopy under dry or humid conditions, provided an understanding of the unique NH3 adsorption/desorption behaviour. The PXRD measurements suggested a crystal structure change of the ZnHCCo NPs after NH3 adsorption. Obtained results suggested a strong NH3 affinity of ZnHCCo, even though the structure was altered by the process. Owing to its high and unique ability, usage of non-rare metals, and cost-effectiveness of zinc, ZnHCCo shows a possibility as an adsorbent for NH3 in practical applications.