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:
Oct. 05, 1999
Filed:
Oct. 21, 1997
Anatole A Klyosov, Newton, MA (US);
George P Philippidis, Boston, MA (US);
Yiannis A Monovoukas, Waltham, MA (US);
Thermo FiberGen, Inc., Bedford, MA (US);
Abstract
Extraction of calcium salts from papermaking sludge or sludge-derived ash is accomplished by mixing with a solution of an inorganic or organic acid. The acid extraction typically results in solubilization of other salts as well, e.g., those of aluminum, magnesium and iron. However, because these non-calcium salts precipitate as hydroxides at lower pH than calcium hydroxide, a caustic (or any other alkaline agent, in a solid or liquid form) is gradually added to precipitate non-calcium salts to facilitate their removal from solution (generally by filtration or centrifugation) prior to precipitation of calcium hydroxide. The desired calcium salt is then precipitated through addition of the appropriate acid anion (either by way of the acid or a salt having greater water solubility than the resulting calcium salt).