Pure alkali phosphate prodn. from crude phosphoric acid - by extn. with organic solvent and treatment with alkaline cpds.

摘要

Pure alkali phosphates are produced from crude phosphoric acid by treating with an organic solvent capable of dissolving >=9 wt. % of water; sepg. the organic phase; treating with alkaline cpds. whereby an aq. and an organic phase are formed; and adding more alkaline cpds. to extract the corresp. mono-, di- or tri-orthophosphates into the aq. phase. The process is improved in that phosphoric acid (which can be preliminarily purified) and an organic solvent are mixed together, whilsts alkali- and/or ammonium ions are pref. added. The organic phase is passed through a series of extractors in countercurrent to an aq. phase contg. alkali- and/or ammonium ions. The resulting organic phase contg. pure H3PO4 and water is treated with alkali- or ammonium salts, oxides or hydroxide, whereby this phase is divided into an aq. phase contg. mono-, di- or tri-orthophosphates and pure organic solvent. Sulphuric acid can be added to free H2PO4; sulphuric acid is subsequently pptd. by treatment with a calcium cpd., esp. a crude phosphate. High-purity alkali phosphates can be produced.