Enhancement of chemically bound gold recovery in post-activation heap leaching of refractory ore

Abstract

This article discusses the main problems connected with heap leaching of chemically bound gold during mining refractory complex ores. It is proposed to prepare refractory ores for heap leaching by electrochemical and photochemical activation of solutions of oxidizing and complexing reagents. The composition of solutions is determined by the mineral composition of the ores. Dispersed and chemically bound gold can occur in various forms in the ores of the sulfide, sulfide–carbonaceous and sulfide–quartz genesis. Therefore, various oxidizing agents should be used when preparing ores for heap leaching. Oxidizing agents actively interact with ore-forming elements that have direct or indirect chemical bonds with clustered gold atoms. Depending on the modes of occurrence of chemically bound dispersed gold, governed by its geochemical associations with the ore-forming minerals, it is proposed to carry out oxidative preparation of refractory ores both at the stage of blasting operations and during pelletizing (agglomeration). Oxidative preparation is implemented with electro-photo-activated solutions with hydroxide-peroxide, sulfuric acid-peroxide, carbonateperoxide, hydroxychloride, sulfuric acid-nitrite-nitrate base. Direct heap leaching of chemically bound gold is proposed to carry out after oxidative treatment with activated solutions. The oxidative treatment includes irrigation of mineral piles with concentrated activated solutions and, then with electrochemically treated water or activated weakly concentrated solution of a complexing agent. Commercial-scale application of heap leaching with oxidation pre-activation in gold ore mining can enable efficient concentration of low-grade difficult ore. In this case, depending on mineral paragenesis of ore and geochemical association of disperse gold, the proposed post-activation heap leaching technology can use process solutions composed of different reagents both at the stage of blasting and during irrigation or pelletizing.