The Study On Bacterial Pre-oxidation Of Refractory Gold Ores In A Bio-chemical Reactor

With large-scale gold mining, free milling resources increasingly depleted, refractory, low grade gold deposit will become the main resources of gold industry. In recent years, biooxidation developed on the basis of microbiological leaching technology had beening attended more and more because of a lower-cost and environment-friendly. At present, it is difficult to improve the bio-oxidation ablity of bioleaching microorganisms, so we need seek some new ways to optimize the growth condition of bacterium. However, bio-oxidation in stirring reactor is a well approach to improve the growth of bacterium, the stirred bioreactor barge up against the high shear rates, suspending solids and the loss of sterility. So that it is imminency to search for some techniques to solve such problems, and make the bioleaching had predominance to other hydrometallurgy ways.Based on the indirect bioleaching mechanism, a new bioleaching process comprising biooxidation and chemical leaching is proposed. The principle of this whole process can be summarized as follows: firstly the leaching solution in the chemical reactor would react with sulfide to produce Fe²⁺, then the Fe²⁺ passed to bioreactor would be biologically oxidized to ferric ions which subsequently be recycled to chemical reactor by a HL-2S peristaltic pump reacting with the sulphide minerals again. The refractory gold ores of Gansu Ping with the process was studied, first of all seven kinds of Acidithiobacillus ferrooxidans in laboratory were used to decompose arsenic-bearing refractory gold ores to select the best strains. BY3 was the optimal At. ferrooxidans. The inoculated ratio 10% v/v, temperature 30℃and pH1.5-2.0 were the optimal parameters for the dissplution of Gannan refactory gold-ore under the conditions of Shaking rate 180r/min. In the biology - chemical reaction process, immobilized At.f compared with free At.f to leach high arsenic refractory gold ores, the results showed that the leaching rate of the former lower than the latter. Therefore, this project adopts free At. f to leach high arsenic-bearing refractory gold ores.In this paper, preteatment of an arsenic-bearing refractory gold ore, which was collected from Pingding in Gasnsu province, was carried out by bioleaching in a novel continuous two-stage bio-chemical reactor. The effects of processing parameters, i.e. ore particle size, temperature, Ag⁺and Fe³⁺ concentration et al., were investigated. Results show that an arsenic extraction rate of 81.79% could be obtained for 5d under the conditions of 70℃, 6g/L of Fe³⁺ (6K) , 5mg/L of Ag⁺and -74μm of particles size, respectively, higher than the control group at low temperature and high temperature control group. It increased leaching rate, shorted leaching time by one half and indirectly reduced the cost of bio- leaching in biological - chemical reactor, therefore, it is feasible in the actual production.