Table of Contents
Table of Contentsii
2.1 HISTORICAL OVERVIEW OF BIOLEACHING4-5
2.2 TYPES OF BIOLEACHING5-7
2.3 GOLD ORES APPLICABLE TO BIOLEACHING7
2.4 PRINCIPLES OF BIOLOGICAL GOLD ORE TREATMENT7-9
2.5 OPTOMIZING THE BIOLEACHING PROCESS9-11
2.6 ADVANTAGES OF BIOLEACHING OF GOLD ORE11
2.7 LIMITATIONS/DISADVANTAGES OF BIOLEACHING OF GOLD ORE 12
Bioleaching has been applied to copper and uranium deposits for many years, but more recently has been applied to gold ore refractory and refractory concentrates. This process involves the oxidation of sulfide, ferrous, and sometimes carbon containing minerals in order to liberate the gold trapped within. This process is possible by use of several bacterial strains which gain energy from the oxidation of reduced sulfur and ferrous minerals. There are three main bioleaching techniques: heap bioleaching, bioreactors and vats. Optimizing the biooxidation of gold ore involves numerous physicochemical, biological and technological factors. There are promising advancements in gold bio-metallurgy that are currently being investigated and maybe employed in the near future. Despite the limitations and slow nature of bioleaching, it offers several advantages over traditional pretreatment techniques. It is a relatively cheap process and offers greater recovery of refractory gold ores and concentrates. It is also relatively environmentally friendly compared to other treatment processes. With stricter environmental regulations and depletion in free-milling gold ores reserves, bioleaching will become increasingly important in the gold mining industry.
Bioleaching is the process of using certain microbial bacteria in order to liberate a metal from ore. This process has been applied to copper and uranium ore for many years, but has more recently been applied to certain types of gold containing ore. Bioleaching of gold can be performed using a number of different techniques and various microbes depending on the factors of the operation in question. These bacteria need to be cultivated and adapted to achieve maximal results. The liberation of the metal by use of bacteria involves a complex chemistry. Optimization of these reactions involves a number of factors. Bioleaching technology is rapidly progressing in complexity and effectiveness. Although bioleaching has limitations, it offers several economical, efficiency and environmental advantages to traditional gold extraction techniques. As environmental regulations become stricter and as gold ore that can be economically processed using traditional techniques continue to be depleted; bioleaching will become ever more important in the gold mining industry. 2.1 HISTORICAL OVERVIEW OF BIOLEACHING
The bacteria used in bioleaching have existed naturally since their evolutionary existence. The ability of these microorganisms to oxidize minerals was first discovered in 1947 in connection with acid mine drainage. By the 1958 bioleaching was first performed in order to liberate metals . Since then, bioleaching has been performed for a number of metal containing ores; most commonly applied to copper and uranium deposits. Only recently has bioleaching been applied to the treatment of gold ore on an industrial scale. Major advances in bioleaching of gold ore were made when Newmont Mining Corporation began laboratory investigations of biooxidation in the late 1980’s. By 1990 mass field pilots had begun on sulfur containing ore, investigating the effectiveness, as well as the economics involved in bioleaching of gold ore. Shortly after, similar...