AlPO4nH2O

AlPO4·nH2O, commonly written as AlPO4·nH2O, is a family of hydrated aluminum phosphate compounds. The precise formula is AlPO4 with n water molecules of hydration, where n varies with synthesis and storage conditions. These hydrates are typically produced as white powders by precipitating aluminum ions with phosphate in aqueous media; they occur as amorphous hydrates or as crystalline aluminophosphate phases.

In the solid, aluminum is bound to oxygen in octahedral coordination and phosphorus forms PO4 tetrahedra, forming a three-dimensional network; water molecules reside in interstitial sites or bind to aluminum, contributing to the hydration state.

Hydrates can be obtained by various routes, including precipitation from Al salts and phosphoric acid, hydrothermal synthesis, and sol-gel processing. Upon heating, they lose water to give anhydrous AlPO4, a chemically robust ceramic material.

The hydrates are generally insoluble in water; they are relatively chemically resistant and thermally stable in the hydrated form; the anhydrous form is very hard and stable up to high temperatures.

Hydrated aluminophosphates serve as precursors to porous aluminophosphate materials used as catalyst supports and adsorbents. They are also employed as fillers in ceramics and flame-retardant formulations. In research, they are studied for phosphate capture and ion-exchange applications.

Powder forms may pose inhalation or mechanical irritation risks; appropriate handling and protection are advised.