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:
Jul. 11, 1995
Filed:
Aug. 01, 1994
Hoechst Aktiengesellschaft, Frankfurt am Main, DE;
Abstract
To remove lead and cadmium from phosphoric acid, alkali solution and aqueous sulfide solution are simultaneously introduced with thorough mixing into a phosphoric acid having a P.sub.2 O.sub.5 content of up to 32% by weight, an iron content of up to 0.3% by weight and an alkali/P ratio of up to 0.30. The temperature of the phosphoric acid which is thoroughly mixed with alkali solution and sulfide solution is adjusted to temperatures of 58.degree. to 72.degree. C. with escape of the excess hydrogen sulfide. To complete the sulfide precipitation, the temperature is lowered to below 45.degree. C. Finally, the precipitated sulfides of the lead and cadmium are separated off from the phosphoric acid.