| 摘要 |
Gold is extracted from an aqueous solution in which it is present as the Au+ thiourea complex, together with compounds of other metals, typically copper and iron, by first absorbing the complexed Au+ ions, together with the iron and copper ions, on an acidic cation-exchanger and then carrying out the following three steps: a) the ion- exchanger is first eluted with aqueous nitric acid, preferably containing some hydrogen peroxide, b) the ion- exchanger is then eluted with an aqueous solution of ammonium nitrate until a neutral reaction is obtained, and c) the Au+ thiourea complex is converted into an Au+ thiosulphate complex, which is liberated from the ion- exchanger by elution with an aqueous solution of thiosulphate. The gold present in the eluate obtained in step c) is then reduced. Step c) gives a solution of the complexed Au+ ions, which is essentially free of other metals and contains considerably more gold than the starting solution. Furthermore, the ion-exchanger is better protected in this process.
|
