METHOD OF PURIFYING WET-PROCESS PHOSPHORIC ACID Russian patent published in 2008 - IPC C01B25/46 

FIELD: chemistry.

SUBSTANCE: method has been developed for phosphoric acid, which contains practically no magnesium ions (for example, acid obtained from kola apatite). Purification method for wet-process phosphoric acid, which includes its extraction by tributyl phosphate in a mixer-settler unit, washing the obtained extract, water re-extraction obtaining re-extract and returning part of it to the washing stage. The washing process is carried out in four steps with the correlation of the organic and water phases Vo:Vw, equals (12-18):1, and re-extraction is carried out with water in two stages, where water in the first stage is supplied in an amount which ensures the correlation Vo:Vw, equals (13-17):1, and the obtained re-extract is returned for washing, and the second stage - water is supplied in an amount which ensures the correlation Vo:Vw, equals (4-6):1. In the re-extract obtained after the first stage of re-extraction, supplied for washing, ammonia is added till the mole ratio is NH₃:H₃PO₄=0.2-0.5.

EFFECT: creation of a purification method of phosphoric acid, not containing significant quantities of magnesium ions, obtaining phosphoric acid suitable for production of food grade salts.

3 cl, 2 tbl, 3 ex