| 摘要 |
The present invention relates to a method for the manufacture of phosphatic products having a very low fluorine content from wet process phosphoric acid. According to the invention the fluorine in the wet process phosphoric acid is removed in the form of potassium fluosilicate, by the reaction of its fluoride components with KH2PO4 formed insitu from KCl or K2SO4 and an amine phosphate salt, the latter resulting from phosphoric acid and an amine selected from the group consisting of a primary-secondary-or tertiary aliphatic amine, a quaternary ammonium base or mixtures thereof. Examples of suitable amines and quaternary ammonium bases are: tri-n-octylamine, ethyl di-n-octylamine, di-n-dodecylamine, di-n-decylamine, tricaprylamine, tri-iso-octylamine etc. The amine constituent appears in the form of a water-immiscible liquid, preferably in conjunction with an organic solvent in which the aliphatic amines and their salts are soluble. The method is very flexible and enables the production of a range of upgraded phosphatic products of different purity grades according to the specific requirement, at yields which are substantially theoretical.
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