Patent ID: 7101522

Claim:
A process for the production of dicalcium phosphate from a phosphate source material comprising the steps of: (a) preparing a solution of phosphoric acid by the action of a suitable mineral acid on a phosphate source material; (b) optionally separating the solution from residual solid materials; and (c) treating the solution with suitable alkaline, calcium material to adjust the pH of the solution to between 3.0 and 4.5; (d) hydrolyzing the solution by diluting it with water to a ratio of approximately 1:7 to about 1:10 monocalcium phosphate to water to form a primary precipitate containing substantially all of the fluoride present as CaF 2 together with some dicalcium phosphate and a primary calcium and phosphate containing solution; (e) separating the primary precipitate formed in step (d) from the primary calcium and phosphate containing solution; (f) dissolving the primary precipitate with phosphoric acid and repeating steps (c), (d) and (e) containing substantially all of the fluoride present as CaF 2 together with some dicalcium phosphate and a secondary calcium and phosphate containing solution; (g) optionally repeating step (f) one or more times to produce a tertiary, quaternary, etc. precipitate and tertiary, quaternary, etc. calcium and phosphate containing solution; (h) combining the calcium and phosphate containing solutions and adjusting their pH to above about 5.5 to precipitate dicalcium phosphate; and (i) recovering the product dicalcium phosphate.