GB1162062A - Phosphoric Acid Purification - Google Patents

Abstract

1,162,062. Purifying phosphoric acid. FMC CORP. 1 Feb., 1967 [1 Feb., 1966; 1 June, 1966], No. 4868/67. Heading C1A. H 3 PO 4 obtained by treatment of phosphatic ores with H 2 SO 4 is purified by extraction with an organic solution of an alkyl, alkoxy alkyl, aryl, or alkaryl phosphate, in amount sufficient to extract 50-85% of the P 2 O 5 values. The organic H 3 PO 4 solution so obtained may then be scrubbed with a pure aqueous H 3 PO 4 solution, e.g. product acid (the used acid being mixed with the crude acid) and is finally stripped with water, which may contain an alkali metal carbonate or hydroxide. The following volume ratios may be used: Organic phosphate : organic solvent .. .. .. 10 : 1 to 0.5 : 1 Organic phosphate solution : crude acid .. .. 1 : 1 to 10 : Organic H 3 PO 4 solution : aqu. H 3 PO 4 solution .. .. 1.0 : 1 to 40 : 1 Scrubbed organic H 3 PO 4 solution : water .. .. 5 : 1 to 12 : 1 The processes may be effected in countercurrent in mixer-settlers, agitated columns or centrifuges, at 20-100‹ C. Suitable organic phosphates and organic solvents are listed (preferred are tri-n-butyl phosphate in kerosene or n-hexane). The crude acid may be treated with ground phosphate rock and Na 2 CO 3 to precipitate Na 2 SiF 6 and CaSO 4 . The product acid may be heated at 110-150‹ C. to vaporize F values, and may be decolorized with charcoal. The stripped organic solution may be purified with active charcoal, alkali wash, or distillation, and recycled. The aqueous raffinate may be used to produce fertilizers, e.g. triple superphosphate.