Production of fluoride-free phosphates
US4086322A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 29, 1975 |
| Grant date | Apr 25, 1978 |
| Priority date | — |
| Expiry date | Aug 29, 1995 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC05D9/02
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
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 calciu…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.