METHOD OF RECOVERING SILVER FROM SILVER-CONTAINING SCRAP Russian patent published in 1998 - IPC

FIELD: precious metal recovery. SUBSTANCE: method is intended for recovering silver from the scrap of electronic and electrotechnical ware containing silver coatings based on brass, beryllium brasses, and pure copper. Scrap is treated with mixture of concentrated sulfuric and nitric acids with 5.0-15.5 vol % of the latter. Treatment is carried out at 30-50 C for 4 to 15 min under mechanical stirring and bubbling reaction medium by compressed air. Desilvered scrap is separated from reaction solution, which is then diluted with 1.5-2 volumes of water. Silver sulfate precipitate obtained is filtered off from mother solution, dried, caked with potassium hydroxide to produce powdered silver metal. Mother solution can be evaporated to form concentrated sulfuric acid, corrected in respect to nitric acid, and returned into the beginning of process. Selective and complete recovery of silver from scrap is accomplished at temperature reduced by 30-50 C, and duration of acid treatment is 2- 7-fold shortened. EFFECT: enhanced efficiency of silver recovery. 3 cl