A Simple Synthesis, Characterization, Kinetics and Thermodynamics of Zinc Ammonium Phosphate, ZnNH4PO4

Zinc ammonium phosphate (ZnNH4PO4) was synthesized via a simple precipitation method at room temperature. Thermal decomposition of ZnNH4PO4 occurred through five stages related to the deamination (1st and 2nd steps) and deprotonated hydrogen phosphate (3rd, 4th, 5th steps) reactions and its final decomposed product at above 600 °C was zinc pyrophosphate (to γ-Zn2P2O7). ZnNH4PO4 and γ-Zn2P2O7 samples were analyzed by XRF, XRD, FT-IR and SEM techniques, which are significant for the further treatments. Kinetic parameters (Ea, A) and thermodynamic functions (ΔH*, ΔS* and ΔG*) calculated on well-known equations have been used to support for five thermal transformation processes, reported for the first time. The kinetic results indicate that the intramolecular dehydration of the protonated hydrogen phosphate groups (3rd, 4th, 5th steps) need higher-energy pathways than the deammonium reactions (1st and 2nd steps) because of harder reactions, more difficulties and lower rates. Additionally, thermodynamic results reveal that all thermal reactions are endothermic and non-spontaneous processes. The obtained data may be useful for industrialists and academicians to apply these zinc phosphates for large roles in industrial applications.