A method for leaching or dissolving gold from ores or precious metal scrap

Abstract

The hydrometallurgical leaching of native gold from gold-bearing ores or the dissolution of gold metal during the recycling of electronic and precious metal scrap is performed every day using hazardous chemicals such as sodium cyanide or aqua regia. These chemicals represent health and safety risks for workers and a serious threat for the environment. However, even if several other reagents are known to dissolve gold at the laboratory scale, none of these are used industrially. Hot mixtures of hydrochloric acid with strong oxidizing compounds are known to generate in-situ nascent chlorine which is capable of dissolving gold effi ciently. In this study, the authors investigated the capability of a hot mixture of hydrochloric acid and ground manganese (IV) oxide to dissolve gold metal either under atmospheric or pressurized conditions. The best result was obtained under a pressure of 639 kPa at 90°C with a dissolution rate of 0.250 g·cm -2 h -1 and it was compared to that reported in the literature for other industrial reagents.

A Novel Process for the Production of Gold Micrometer-Sized Particles from Secondary Sources

“…, respectively, which is relatively large compared with the rates obtained in the previous investigations, 12,13) but small compared with rates obtained in our previous research using CuBr 2 .…”

Sodium peroxide fusion for reliable determination of gold in ores and metallurgical samples

“…Subsequent testing after 48 hours confirmed quantitative Au recoveries, indicating that any colloidal Au formed during leaching of the fusion cake was dissolved by H 2 O 2 acting as an oxidant in acidic solution, eqn (5). 33 All subsequent analytical work was performed using 2 M HCl to leach the fusion cakes.…”

Pressure cyanide leaching for precious metals recovery

“…(All equations are presented in the Equations table on page 46.) Ferrous ions produced by Equations 1 and 2 are subsequently oxidized to ferric ions, as shown in Equation 3.…”

“…During the mine's short history, efforts have been made to reduce costs and increase production through improved process developments. 1,2 At the present time, cyanidation has superseded all previous leaching processes, particularly chlorination, 3 because of its ability to effectively and economically treat ores containing as little as 1-3 g/ton gold. The precious metals are dissolved in a dilute solution of sodium cyanide, which is recycled after precipitation of the precious metals with zinc dust.…”