Process for the removal of impurities from wet process phosphoric acid

Abstract

Abstract Impurities are removed from wet-process phosphoric acid containing known quantities of Ca, Al, Si, F and sulphate compounds by adjusting the mole ratios of Al to Si in the acid to 1:0.8 to 1 and Al to F to 1:12 to 16 and adding a soluble calcium orthophosphate in an amount sufficient to react wiIh the impurities and form a complex crystalline solid which can be separated. The ratios of Al:Si:F-: So4-: Ca++ lie within the range 1:1:12-16: 1.5-2: 4-8. Aluminium may be added as the metal or in the form of a soluble alumina and fluorine as hydrofluoric acid. Examples relate to batchwise and continuous processes.

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