The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 17, 1977
Filed:
Jul. 28, 1975
Peter T Chiang, Monroeville, PA (US);
United States Steel Corporation, Pittsburgh, PA (US);
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.