Phosphate

Phosphate refers to the salt or ester of phosphoric acid and to the phosphate ion, PO4^3−. In chemistry, phosphate groups form esters and anhydrides that are widespread in biology and industry.

In nature, phosphate occurs mainly in minerals such as apatite (calcium phosphate) and related calcium phosphates. Phosphate rocks are mined for the production of phosphorus-containing fertilizers; phosphate concentrations in rocks vary by deposit.

The term phosphate covers several species: orthophosphate (PO4^3−), dihydrogen phosphate (H2PO4−), and hydrogen phosphate (HPO4^2−). Phosphates also form condensed anions such as pyrophosphate (P2O7^4−) and long-chain polyphosphates.

Industrial production begins with mining phosphate rock and processing to phosphoric acid by wet or thermal processes; phosphoric acid is used to manufacture phosphate fertilizers, including monoammonium phosphate, diammonium phosphate, and triple superphosphate.

In biology, phosphate is essential for energy transfer (ATP), storage (phosphocreatine), nucleic acids, and membrane lipids. Animal and plant tissues contain hydroxyapatite in bones and teeth.

Environmental concerns include eutrophication caused by excess phosphates entering waterways; phosphate removal from wastewater and phosphate-free detergents have been adopted in many regions to mitigate nutrient pollution.