Open AccessRegeneration Process of Ammonia-Absorbed Zirconium Phosphate to Zirconium Phosphate
Author(s) -
Masakuni Yamaguchi,
Yoshitsugu Kojima,
Hiroki Miyaoka
Publication year - 2022
Publication title -
acs omega
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.779
H-Index - 40
ISSN - 2470-1343
DOI - 10.1021/acsomega.2c01507
Subject(s) - anhydrous , zirconium , zirconium phosphate , inorganic chemistry , ammonia , chemistry , phosphate , nuclear chemistry , organic chemistry
Zirconium phosphate [Zr(HPO 4 ) 2 ·H 2 O] absorbs 2 mol(NH 3 )/mol[Zr(HPO 4 ) 2 ·H 2 O] with a low equilibrium plateau ammonia concentration of around 1 ppm in water. In this study, in order to investigate the regeneration process of ammonia-absorbed zirconium phosphate [Zr(NH 4 PO 4 ) 2 ·H 2 O], Zr(NH 4 PO 4 ) 2 ·H 2 O was heat-treated above 353 K under an inert gas. Then, the structures of the heat-treated samples were evaluated using powder X-ray diffraction and thermogravimetry-mass spectrometry measurements. Zr(NH 4 PO 4 ) 2 ·H 2 O started to desorb ammonia and the crystal water at 353 K. Then, Zr(NH 4 PO 4 ) 2 ·H 2 O was changed to the anhydrous monoammoniate [Zr(NH 4 PO 4 )(HPO 4 )] at 473 K and formed anhydrous zirconium phosphate [Zr(HPO 4 ) 2 ] at 673 K. The anhydrous zirconium phosphate and the anhydrous monoammoniate reabsorbed ammonia in ammonia water. Those initial absorption rates were small compared with Zr(HPO 4 ) 2 ·H 2 O. The slow kinetics of the anhydrous zirconium phosphate corresponded to the small interlayer distances. The ammonia concentration composition isotherms indicated that the anhydrous zirconium phosphate and anhydrous monoammoniate have a low ammonia equilibrium plateau concentration of around 1 ppm in ammonia water. Zr(NH 4 PO 4 ) 2 ·H 2 O is formed from Zr(NH 4 PO 4 )(HPO 4 ) by the reabsorption of ammonia and water after 1-10 cycles. We found that zirconium phosphate is an ammonia remover which can be used repeatedly at 473 K.