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:
Sep. 04, 1990
Filed:
May. 15, 1989
Ranko Crnojevich, New Orleans, LA (US);
Edward I Wiewiorowski, New Orleans, LA (US);
Andrew B Case, Harvey, LA (US);
AMAX Inc., New York, NY (US);
Abstract
A method is provided for treating sludge containing substantial amounts of chromium, aluminum and iron and residuals of other elements. The method comprises forming a slurry of the sludge in water at a temperature ranging from ambient to 150.degree. F. with the specific gravity of the slurry ranging from about 1.05 to 1.25, and adding a mineral acid to the slurry to provide a pH ranging from about 0.1-3 to dissolve selectively the aluminum and the chromium and leave a solids residue containing gangue material comprising an oxidized iron compound, calcium sulfate, calcium fluoride, calcium silicate among other solids. The pH of the solution is controlled at range of about 2 to 3.5 to precipitate undesirable elements, including iron, without substantially adversely affecting the dissolved chromium and aluminum. The chromium/aluminum-containing solution is separated from the solids therein to provide a substantially purified solution of chromium/-aluminum, and the pH of the solution raised to a range of about 12 to 13.8 to precipitate chromium as chromium hydroxide and provide a pregnant aluminate solution. The chromium hydroxide-containing solution is then subjected to solid/liquid separation to extract chromium hydroxide therefrom and providea pregnant aluminate solution which is thereafter treated to recover alumina therefrom.