Improvements in or relating to the recovery of precious metals from ores or preciousmetal bearing deposits

摘要

Precious metals are recovered from ores by extraction with dilute alkaline cyanide solution, subjecting the solution to a conditioning operation which renders the solution capable of actively reacting with a metallic precipitant, deoxides the solution, and neutralizes alkalinity to an extent sufficient to afford a pH value of from 6-8,4, and then contacting the solution with a metallic precipitant such as zinc or iron. The conditioning operation may comprise the addition of sodium or calcium bisulphite, sulphur or carbon dioxides, either singly or in combination, a suitable source of mixed dioxides being flue-gas. Before the addition of bisulphite, the solution may be neutralized with sulphuric acid and the bisulphite may be formed by interaction between the alkali or alkaline earth ion in the solution and sulphurous acid. Reference has been directed by the Comptroller to Specification 442,315.