SOLVENT EXTRACTION PROCESS FOR PREPARING PHOSPATE SALTS WITH RECOVERY OF ORGANIC SOLVENT FROM THE AQUEOUS RAFFINATE

摘要

Phosphate contg. salts are prepd. by a) producing an aq. layer of phosphoric acid, contg. a non-water miscible organic solvent and metallic impurities in equilibrium with an organic layer comprising a soln. of phosphoric acid in the non-water-miscible solvent b) sepg. the two layers c) treating the aq. layer to form phosphated salts and d) sepn. of the solvent is characterised in that the aq. layer is treated with ammonia or a base or salt of ammonia, alkali metals or alkaline-earth metals to give an aq. soln. contg. phosphoric acid and ammonium or alkali- or alkaline earth metal cations followed by sepn. of the aq. phase from the organic solvent. Used in prodn. of phosphated slats particularly for use as fertilisers e.g. NH4H2PO4 or may be purified further to give feed quality prods. e.g. calcium phosphate suitable as a feed additive. The process allows recovery of some of the organic solvent in the purified aq. phosphoric acid and reduces risk of explosions and fires.