Thermal decomposition kinetics and reversible hydration study of the Li2Zn(HPO4)2·H2O

The dilithium zinc hydrogen phosphate monohydrate (Li2Zn(HPO4)2·H2O) was synthesized at the ambient temperature by using zinc acetyl acetonate monohydrate, phosphoric acid and lithium hydroxide monohydrate. The thermal stability of the Li2Zn(HPO4)2·H2O was studied by non-isothermal kinetic method (Ozawa and Kissinger) from the differential scanning calorimetric (DSC) data. The studied hydrate undergoes two endothermic thermal transformations, which the first transformation is due to the release of water molecule of crystallization and the second one is due to the release of water of constituent from HPO42− anions and transforms to P2O74−. The activation energies (Ea) calculated for the dehydration step and decomposition step of the Li2Zn(HPO4)2·H2O from different methods were found to be consistent. The dehydration and rehydration processes of the synthesized compound were investigated and found that the water of crystallization can be removed and rehydrated without the disrupting the structure of the material, provided it is not heated beyond 200 °C. The dehydration and rehydration processes of the synthesized Li2Zn(HPO4)2·H2O exhibits similar property to the zeolite.

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