Alternatives to cyanide in the gold mining industry: what prospects for the future?

Abstract

This paper reviews a series of alternative lixiviant systems for the recovery of gold from ores and concentrates. For over 100 years, cyanide has been the leach reagent of choice in gold mining because of its high gold recoveries, robustness and relatively low costs. The environmental damages resulting from its mismanagement, however, have initiated widespread research aimed at identifying and developing less toxic leaching agents. The most widely-researched alternative lixiviants for gold ores are examined in this paper, but it is evident that none has yet made any significant inroad into the dominant position of cyanide as the reagent of choice at the vast majority of gold mines worldwide.

A Review of Thiosulfate Leaching of Gold: Focus on Thiosulfate Consumption and Gold Recovery from Pregnant Solution

“…The total reaction of thiosulfate leaching of pure gold is indicated in Equation (1), and the values of standard Gibbs free energy for Equations (1)- (13) were all calculated based on the thermodynamic data in the literature [26]. The essence of this reaction is an electrochemical process consisting of the oxidation of gold at the anode and reduction of oxygen at the cathode [27,28].…”

“…Favorable reaction conditions are important to control thiosulfate consumption and promote gold dissolution [1]. Although gold dissolution is evidently enhanced by a high Cu(II) concentration, the thiosulfate consumption deriving from its oxidation by Cu(II) also increases markedly.…”

“…Cyanidation has been the predominant gold leaching technique since it was first put forward by John Stewart MacArthur in the 1880s [1] because of its simple process and low cost. However, unluckily, cyanide is highly toxic, and there have been some serious environmental accidents occurring around the world caused by the leakage of cyanide from metallurgical plants [1][2][3].…”

“…However, unluckily, cyanide is highly toxic, and there have been some serious environmental accidents occurring around the world caused by the leakage of cyanide from metallurgical plants [1][2][3]. Due to of environmental concerns, cyanide leaching has been banned in many regions at present.…”

Extractive Metallurgy: Efficiency and Eco-friendliness

“…1 However, it suffers technical problems caused by other associated elements in the ores, such as copper and zinc, which often disrupt the process by forming copper-cyanide complexes and zinc-cyanide compounds, resulting in increased usage of cyanide. To address this issue, in the second article, ''An Improved Process for Precipitating Cyanide Ions from the Barren Solution at Different pHs,'' Gabriela V. Figueroa et al report on the use of sulfide precipitation for removing copper, zinc, and other species from barren cyanide solutions.…”