Adaptability of Gold Leaching from Different Ores in Highly Stable Alkaline Thiourea Solutions
高稳定性碱性硫脲体系对不同类型金矿的适应性

In order to examine the flexibility of leaching different gold ores in alkaline thiourea system, six kinds of gold concentrates and calcines with different physical and chemical properties were chosen as objects, their chemical components and phases were analyzed, and the leaching behaviours were also investigated. The results indicated that stablizing reagents Na2SO3 and Na2SiO3 decreased the decomposition rate of alkaline thiourea solution greatly. However the stable effect of Na2SiO3 on alkaline thiourea was obviously better than that of Na2SO3 as well, and the decomposition rate of alkaline thiourea reduced from 72.5% to 33.8% with adding 0.3 mol/L Na2SiO3. K3Fe(CN)6 was the soft oxidizing reagent being suitable for alkaline thiourea system. The phases of gold ores were almost not changed before and after leaching in alkaline thiourea solution. There exist a large number of substances consuming alkali in the gold ores. During the leaching process, pH of the system dropped from 12.5 to 7.0 quickly, while the stablizing reagent Na2SiO3 could maintain pH of the system at about 12, which was propitious to the leaching process. The leaching rates of the coexisting metals in gold ores were less than 0.1% in alkaline thiourea system, which indicated that gold leaching in alkaline thiourea retained excellent selectivity. The alkaline thiourea system was suitable for leaching the pretreated oxidized gold ores in which the main phase was SiO2. The gold leaching rate reaching up to 82.68% suggests promising potential in commercial gold leaching processes.