METHOD OF RECOVERING PRECIOUS METALS FROM SECONDARY MATERIAL, PREDOMINANTLY FROM TIN-LEAD SOLDER ALLOY Russian patent published in 1997 - IPC

FIELD: waste disposal. SUBSTANCE: method includes melting and subsequent granulation of starting material, nitric acid leaching, and filtration of resulting slurry to produce solid residue containing gold and tin dioxide. Residue is washed out with hot water and calcined, and to solution containing lead nitrate, precipitating agent is added to produce lead chloride-containing slurry. Slurry is filtered and lead chloride is washed with aqua regia and then with water, after which lead chloride is dehydrated. Calcined residue from nitric acid leaching operation is neutralized, produced slurry filtered, and separated tin dioxide washed with aqua regia and then with hot water. Gold-containing solution is filtered and obtained gold slime washed out, dehydrated, dried, melted, and subjected to affinage. EFFECT: enlarged precious metals' resource.