Research On Mechanical Activation Properties And Leaching Test Of Gold-bearing Sulfide Minerals

The study on the pretreatment of refractory gold ores by mechanical activation has been of great interest to numerous researchers since mechanical activation can provide a flexible mechanical force to change physicochemical properties of minerals.Some researchers employed the mechanical activation pretreatment of minerals to improve their hydrometallugical processing such as pyrite,chalcopyrite,galena,sphalerite,molybdenite and so on.However,the researches on mechanochemical activation of pyrite and mechanical activation of arsenopyrite are rarely reported.In this study,high pure pyrite and pure arsenopyrite are used as raw materials.The effect of a new pretreatment method,namely mechanical activation,on the solid-state and dissolution properties of pyrite and arsenopyrite,respectively.The main conclusion is summarized as follows:(1)The results of mechanically activated pyrite indicated that the optimum particle distribution,minimum particle size value of 6.46 ?m and maximum specific surface area(BET)value of 1.547 m2/g can be observed at milling speed of 400 r/min.The images of scanning electron microscopy(SEM)showed that the particle surface of pyrite formed micro-nano particle and amorphization degree significantly increased with the increase of milling speed.Precise information about structural changes of mechanically activated pyrite was obtained using X-ray diffraction(XRD)line profile analysis methods.With increase in milling speed,no phase transformation was found.However,the amorphization degree,lattice disorder and crystallite size of arsenopyrite ascended to 42.54%,increased from 0.059%to 0.220%,and decreased from 369.5 nm to 150.2 nm,respectively.Finally,the leaching tests of arsenopyrite were carried out by sulfuric acid solution.The results showed that contrasted with unactivated arsenopyrite,total arsenic extraction from arsenopyrite stands at roughly 19.04%under the optimum milling speed(580 r/min).(2)XRD analysis of mechanochemically activated pyrite revealed that during the incomplete mechanochemical reaction,new phase of troilite is detected along with previous phases of pyrite and iron.After pyrite was mechnochemically activated,the amorphization degree of increased to 78.98%,lattice disorder ascended from 0.059%to 0.190%and crystallite size of decreased from 359.5 nm to 140.3 nm.The iron extraction rate in leaching of mechanochemically activated pyrite for 5 h,attained 61.36%under milling optimum speed of 580 r/min.And in comparison with crystalline size and lattice disorder,the new phase formation and amorphization degree take dominant status in leaching of pyrite.(3)The analysis of particle size and specific surface area indicated that the particle size of arsenopyrite decreased rapidly at first and then increased slightly with increase milling speed.The optimum particle distribution,minimum particle size value of 2.36 ?m and maximum BET value of 2.667 m2/g can be observed at milling speed of 300 r/min.The morphology of pyrite at different milling speeds was observed by scanning electron microscopy(SEM),and it was found that the surface of arsenopyrite formed micro-nano particles and amorphization degree significantly increased with the increase of milling speed.XRD analysis results showed that with increase in milling speed,no phase transformation was occurred,but the amorphization degree of arsenopyrite increased to 72%,microstrain of increased from 0.014%to 0.097%and crystallite size decreased from 75.6 nm to 56.0 nm.The characteristic peaks of 217.2 and 273.7 cm-1 of arsenopyrite were analyzed by Raman spectroscopy.It was found that the vibration of the characteristic peak located at 273.7 cm-1 is more sensitive to the mechanical stress.Finally,the leaching tests of arsenopyrite were carried out by Fe2(SO4)3 solution.The results showed that contrasted with unactivated arsenopyrite,total arsenic extraction from arsenopyrite has doubled to nearly 40.16%under the optimum milling speed(300 r/min).(4)The leaching kinetics indicated that leaching rate depended on temperature and milling speed.Leaching process of arsenic from arsenopyrite included two stages.The activation energy for the first stage is 44.7 kJ·mol-1,and chemical reaction is rate controlling step.For the second stage,the activation energy is 48.8 kJ·mol-1,and it is also controlled by chemical reaction.The activation energy of mechanically activated arsenopyrite leaching is 31.8 kJ·mol-1 and 7.6 kJ·mol-1,separately.It happened that control step mixed of diffusion and chemical reaction transformed to diffusion control with along leaching time.