Chemistry of inorganic compounds – Phosphorus or compound thereof – Oxygen containing
Patent
1975-07-28
1977-05-17
Spear, Jr., Frank A.
Chemistry of inorganic compounds
Phosphorus or compound thereof
Oxygen containing
210 21, 423315, 423321S, C01B 1516
Patent
active
040242250
ABSTRACT:
Wet-process phosphoric acid is partially purified by extraction with an organic solvent followed by scrubbing with a portion of the aqueous phosphoric acid from a water-stripping unit, then water-stripping and base-stripping. At the water-stripping stage, all the remaining impurities and approximately two-thirds of the P.sub.2 O.sub.5 are transferred from the organic to the aqueous phase, which renders the other one-third P.sub.2 O.sub.5, subsequently recovered by base-stripping, essentially free of impurities. The bulk of the aqueous phosphoric acid from the water-stripping is purified further by precipitating the impurities with an alkali metal hydroxide or carbonate. The precipitate is filtered off and the filtrate used for base-stripping. The resulting aqueous solution from base-stripping is adjusted to a desired alkali metal-to-phosphate ratio and used for manufacture of high purity alkali metal phosphate in general and particularly sodium tripolyphosphate.
REFERENCES:
patent: 3707357 (1972-12-01), Chiang
patent: 3767769 (1973-10-01), Winand et al.
patent: 3867511 (1975-02-01), Chiang et al.
patent: 3914382 (1975-10-01), Williams
Krayer William L.
Spear, Jr. Frank A.
United States Steel Corporation
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