REVIEW OF MODERN PROCESSING TECHNOLOGIES OF REFRACTORY GOLD ORES AND CONCENTRATES WITH USE OF NITRIC ACID

Abstract

The relevance. The refractoriness of gold-bearing ores is caused by two factors: the first is the fine dispersion of gold in sulfide minerals, and the second is the presence of carbonaceous matter, which is responsible for the pre-robbing, leading to an inevitable decrease in gold recovery. In the modern gold mining industry, there are many ways to process refractory gold with carbonaceous matter content up to 1 %, but its higher concentrations still cause big problems. One of the most interesting and promising ways to minimize the effect of carbon on gold recovery is the use of nitric acid, since this reagent can, on the one hand, intensify oxidation or removal of carbonaceous matter, and, on the other hand, passivate its surface and, thus, significantly reduce the sorption activity of carbonaceous matter. The relevance of this work is caused by the lack of technology in the modern gold mining industry that allows processing high carbonaceous raw materials and the promising use of nitric acid in gold hydrometallurgy. The aim of the work was to substantiate the importance of using nitric acid in the technology of autoclave oxidation of refractory gold-bearing concentrates. Results. The authors have carried out a review of modern methods of refractory gold processing, the main advantages and disadvantages of each were identified. It was found that none of the methods allows efficient processing of high-carbonaceous raw materials due to the low degree of carbonaceous matter oxidation/passivation, which is responsible for the pre-robbing process. The paper presents technologies for processing gold-bearing raw materials in nitric acid media; it is shown that nitric acid can be used not only as the main oxidant, but also as a catalyst for chemical oxidation reactions and a passivator of the carbonaceous matter surface. The unique properties of nitric acid described in the work can be successfully applied in the autoclave hydrometallurgy of gold.

Keywords

• refractory gold-bearing ores
• autoclave oxidation
• bioleaching
• oxidative roasting
• nitric acid technologies
• nitrate ions
• organic carbon
• carbonaceous matter
• preg-robbing