Thermodynamic and Spectroscopic Analyses of Zirconium Phosphate-Absorbed Ammonia

Abstract

Zirconium phosphate is insoluble in water and has a large ammonia storage capacity with a low ammonia plateau concentration in water. In this study, the thermodynamics of ammonia on zirconium phosphate (ZrP) and the local structure such as the interaction between ammonia and ZrP have been investigated using the temperature dependence of ammonia concentration composition isotherm (CCI) measurements, 31 P magic angle spinning nuclear magnetic resonance ( 31 P MAS NMR), and Fourier transform infrared (FT-IR) spectroscopy. The standard enthalpy changes ΔH 0 of ZrP-absorbed ammonia (1 mol(NH 3 ) mol −1 (ZrP):ZrP-NH 3 and 2 mol(NH 3 ) mol −1 (ZrP):ZrP-2NH 3 ) were calculated to be ≤ −111 and −64 kJ mol −1 (NH 3 ), respectively. 31 P MAS NMR and FT-IR indicated that the local structures of ZrP-NH 3 and ZrP-2NH 3 were different. It was suggested that nitrogen in ammonia reacts with hydrogen in the phosphate group to form a N−H covalent bond in NH 4 + having hydrogen bonds, although the number of hydrogen bonds in ZrP-NH 3 was smaller than that in ZrP-2NH 3 .

Unexpected structural/motional mode of water intercalated into an α‐crystalline zirconium phosphate deduced by 31P and 2H solid‐state MAS NMR spectra

“…Variations in 31 P chemical shift for the hydrated and anhydrous zirconium phosphate intercalates have been interpreted earlier in terms of hydrogen bonds, formed by the interlayer phosphate group, where a donor hydrogen bond leads to displacement Δδ (iso) of $ 3 ppm, while Δδ (iso) of approximately À2 ppm corresponds to an acceptor hydrogen bond. [16] Following this rule, the low-field resonance of HPO 4 groups at δ of À21.4 ppm could be attributed to hydrogen bond P OH˙˙˙OD 2 [11] (Figure 1). Upon formation of such a bond, rates of rotations around the P O axis in the structurally different HPO 4 groups of compound 1-D 2 O, which cause phosphorus NMR relaxation by the dipolar proton-phosphorus mechanism, [17] will have to differ.…”

Trace Ammonia Equilibrium Pressure of Zirconium Phosphate in Moisture

“…Then, zirconium phosphate with different ammonia absorption capacities was prepared by vacuum drying for at least half a day. At this time, it has been confirmed that the ammonia and crystalline water in the samples are hardly released, and the water on the surface of the samples is removed. , …”

Regeneration Process of Ammonia-Absorbed Zirconium Phosphate to Zirconium Phosphate

“…Zr(HPO 4 ) 2 ·H 2 O showed the greatest amount of ammonia absorption among insoluble ammonia absorbing materials such as Prussian blue. 13 , 15 , 16 However, there is no research on recycling back to Zr(HPO 4 ) 2 ·H 2 O after regeneration of [Zr(NH 4 PO 4 ) 2 ·H 2 O].…”

“…Zr(HPO 4 ) 2 •H 2 O showed the greatest amount of ammonia absorption among insoluble ammonia absorbing materials such as Prussian blue. 13,15,16 However, there is no research on recycling back to Zr(HPO 4 ) In this report, we have studied a heat treatment method under an inert atmosphere to regenerate zirconium phosphate from ammonia-absorbed Zr(HPO 4 ) further purification. Various concentrations of ammonia water were prepared using 10 wt % ammonia water from KENEI Pharmaceutical Co., Ltd., diluting with ion exchange water.…”

“…In our previous studies, , we have reported that zirconium phosphate [Zr­(HPO 4 ) 2 ·H 2 O] has a high ammonia absorption capacity of 10.2 wt % with the low equilibrium concentration in ammonia water [6.7 mmol (NH 3 )/g, ammonia equilibrium concentration: below 1 ppm at about 298 K]. Zr­(HPO 4 ) 2 ·H 2 O showed the greatest amount of ammonia absorption among insoluble ammonia absorbing materials such as Prussian blue. ,, However, there is no research on recycling back to Zr­(HPO 4 ) 2 ·H 2 O after regeneration of [Zr­(NH 4 PO 4 ) 2 ·H 2 O].…”