| As a refractory gold ore, micro-disseminated gold deposits are a major gold resource in China. It is of great significance to strengthen the development and use of micro-disseminated gold deposits. In this research, on the basis of studying ore properties, experimental study on non-cyanide leaching was carried out for the micro-disseminated gold ores of Guizhou. As a result, a appropriate process and better test conditions were determined through the methods and optimization study of non-cyanide agents, ore pretreatment and pretreatment-leaching process. Different test methods were applied to the comparative analyses of raw ore, pretreated sample and leach residue. Furthermore, some discussions of mechanism of pretreatment and gold leaching system were made from solution chemistry and thermodynamics. By chemical element analysis, mineral composition analysis, phase of gold analysis, SEM analysis and particle size analysis, the researches on ore prosperity were carried out in detail. The result shows that the mainly useful elements is Au, the grade of which is 3.46 g/t. The content of silver, copper, lead, zinc, antimony and arsenic is low, and with a certain amount of organic carbon in this ore. The ore is mainly composed of quartz, calcite, pyrite and clay minera. The scattered distribution of gold turned out liberation and relation gold rate is 22.96 %, while the ratio of gold in sulphides, silicates and carbonates are 34.24 %, 23.73% and 19.07 %, respectively. The gold are mainly distributed in the coarse and fine grained, resulting in its inhomogeneity. The above analysis shows that it is difficult to raising gold recovery through a single enrichment method, and the exposure of wrapped gold is the key to effective gold leaching.According to the research of ore property, four non-cyanide agents JQ, thiosulfate, thiocyanate and SZS were applied to direct leaching of gold ore at room temperatures and pressures, comprehensive considering SZS for better leaching reagents, the leaching rate of which was up to 60.53 %. After determining leaching method, four means, conventional roasting, strong oxidation, pretreatment of strong alkaline medium, chemical compounds M-1 and M-3, were taken to the research of pretreatment, and M-1 and M-3 were chosed for the better pretreatment reagents.The research on optimization of process of pretreatment and leaching shows that the pretreatment and leaching process are preferably at normal temperature and pressure, non-removal reagent after pretreatment. The conditions were ultimately determined as follows: the recommended dosages of M-1 and M-3 are 50 kg/t and 105 kg/t, the inflating volume is 1.8 m3/h, with a liquid-solid ratio of 2:1, stirring for 24 h in the pretreatment; while the suggested doses for Cu2+, NH3·H2O and Na2SO3 are 0.06, 1and 0.15 mol/L, respectively, with a liquid-solid ratio of 3:1 and p H value of 11, stirring for 4 h during the leaching. Mixing leaching agent has shelf-life of about 10 days, turned out its good stability. Under above conditions, the gold leaching rate is steady at 84 %~86 %. The methods including XRD, XRF, phase analysis, scanning electron microscopy(SEM), Raman spectrum and XPS were taked to characterization analyses of raw ore, pretreated sample and leach residue.The results show that, the chemical environment of elements O, Si, Ca, Fe and S on the surface of mineral is changed after pretreatment and leaching. The content of Si and S is decreased with dissolution of Si O2, oxidization of pyrite into Fe2O3 and SO42- under the effect of pretreatment. In the meantime, the distribution rate of gold in silicate and pyrite is reduced, while the rate of liberation and relation gold is increased, as well as gold in carbonates. This can be explained that gold in sulfide and silicate are mostly exposed or dissociated into free gold, but a new generation of carbonate wrapping gold again after pretreatment.The Gibbs free energy ?G of chemical reaction and Eh-p H diagrams about pretreatment were analysied in the research, which suggest that when oxidizer exsiting in the solution, and the reaction time is long enough, most pyrite will be oxidized to Fe2O3 and SO42-. The p H and ionic strength of solution significantly affects the dissolution of quartz, and higher p H is conducive to the dissolution of quartz. Meanwhile, the dissolution of quartz is little impacted by substance diffusion, but mainly restricted by chemical reaction of the solution. The mechanism of SZS-copper-ammonia system was discussed from solution chemistry and thermodynamics, suggesting that SO32- may be contribute to the stability of S2O32-, but will accelerate the reaction of Sx2- to S2O32-. The p H value, Cu(NH3)42+ and SO32- concentration of the solution directly and indirectly affect the leaching effect. Key words: micro-disseminated gold ore; ore prosperity; pretreatment; non-cyanide leaching;... |
PDF Full Text Request