Production of fluoride-free phosphates

Details Production of fluoride-free phosphates Production of fluoride-free phosphates

1975-08-29

1978-04-25

Vertiz, O. R.

Chemistry of inorganic compounds

Treating mixture to obtain metal containing compound

Alkaline earth metal

423166, 423167, 423309, 423319, 423323, C01B 2516

Patent

active

040863220

ABSTRACT:
A method is disclosed for the acidulation of phosphate rock and the production of substantially pure alkali metal phosphates, calcium phosphates, and phosphoric acid which are essentially free of fluorides and recovery of the fluorine values from the starting phosphate rock in useful form. The steps of the method comprise initial acidulation of phosphate rock with a phosphoric acid solution containing sufficient alkali metal values to provide R.sub.2 O in the system, where R is alkali metal, to solubilize the phosphates and form an insoluble precipitate comprising a mixture of impurities, sand (SiO.sub.2) and the fluorides, from which the fluorides can be recovered in usable form. In preferred embodiments, after removal of the precipitate containing the fluorides, a portion of the solution of phosphoric acid and calcium phosphate is reacted with sulfuric acid and RHSO.sub.4 or R.sub.2 SO.sub.4 where R is alkali metal, to form a solution of RH.sub.2 PO.sub.4 and phosphoric acid and at least a portion of the RH.sub.2 PO.sub.4 and phosphoric acid solution is recycled to the initial acidulation to provide the R.sub.2 O and phosphoric acid makeup. The remainder of the solution of calcium phosphate and phosphoric acid may be further processed for recovery of useful products such as monocalcium phosphate and/or dicalcium phosphate, phosphoric acid, alkali metal phosphates, and calcium sulfate.

REFERENCES:
patent: 3512927 (1970-05-01), Betts
patent: 3554694 (1971-01-01), Barker et al.
patent: 3792151 (1974-02-01), Case
patent: 3795728 (1974-03-01), Scheel
patent: 3840640 (1974-10-01), Drechsel
Chemical Abstracts, vol. 77, p. 106, 1972, Item 141900V.

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