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. 12, 1998
Filed:
Mar. 11, 1997
Katutoshi Narita, Ibaraki, JP;
Nippon Mining & Metals Co., Inc., Tokyo, JP;
Abstract
The known method comprises the following steps. (1) the de-copperized anode slime is chlorination-leached with HCl and H.sub.2 O.sub.2. (2) Na.sub.2 CO.sub.3 is added to the chlorination-leach residue of (1). (3) NH.sub.3 is added to the residue of (2). (4) Distillation of NH.sub.3 to remove NH.sub.3 contained in the ammonia leach solution of (3). (5) Distillation residue is washed with water to yield refined AgCl. (6) Conversion of AgCl to Ag.sub.2 O. (7) Reduction of Ag.sub.2 O to Ag. In order to enhance the purity of the reduced silver, the present invention provides the following improvements (a) to (d). (a) Dechlorination (2) with the use of Na.sub.2 CO.sub.3 is carried out at ambient temperature. (b) After dechlorination, the residue is washed with hot water. (c) Sulfuric acid is added instead of carrying out distillation (4). (d) Prior to conversion (6), the chlorination is again carried out.
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