Reaction between calcium phosphate and fluoride in phosphogypsum

Phosphogypsum is the principal by-product produced by the wet processes involved in the manufacture of phosphoric acid, and generally contains an amount of fluoride that needs to be fixed or removed. Calcium hydrogen phosphate dihydrate (DCPD) reacts with fluoride ions in solution to form fluorapatite (FAp) in a reaction that is both selective and sufficiently efficient. We investigated the reaction between DCPD and the fluoride in phosphogypsum. The results demonstrated that the fluoride in phosphogypsum is able to be fixed by the reaction with DCPD, forming stable fluoride compounds such as fluorapatite.