Research On Ultrasonic Enhanced Pretreatment Of Refractory Gold Ore

The carrier minerals of gold in refractory gold deposits are usually metal sulfides,mainly pyrite and arsenopyrite.The most effective way to develop and utilize refractory gold ore is oxidation pretreatment,which aims to destroy the inclusion of sulfide in gold and make it easy to leach.The pretreatment process of chemical oxidation has the advantages of fast reaction speed,no waste gas pollution,simple process,strong adaptability and development potential.In this paper,a new idea of pretreatment leaching of refractory gold ore by ultrasonic enhancement is put forward based on the study of refractory gold ore in Yunnan Province.The main research contents include:?1?the pretreatment process and mechanism of Na OH-Na₂S under ultrasonic condition:In order to eliminate the adverse effect of antimony on the extraction of gold from refractory gold ores,the selective removal of antimony from refractory gold ores by sodium sulfide leaching under sodium hydroxide system is proposed in this study.The effects of sodium sulfide?0.5?2 mol/L Na₂S?,sodium hydroxide?0.5?2.5 mol/L?,temperature?20?80??and ultrasonic power on the leaching rate of antimony were studied.The orthogonal optimization analysis shows that the order of influence factors is:temperature>ultrasonic power>sodium sulfide concentration>ultrasonic time.The best leaching conditions are:time 60min,temperature 55?,concentration of sodium sulfide 2 mol/L,ultrasonic power 1500 W.Under these conditions,the average leaching rate of antimony is 94.50%.Under the same conditions,the leaching rate of antimony without ultrasonic treatment is only 58.37%.Compared with the literature,the temperature,time,Na OH and Na₂S concentration of antimony removal were greatly reduced.The leaching rate of gold increased from 13.35%to40.56%after antimony removal.The leaching rate of antimony ore gold by ultrasonic enhanced leaching is 68.90%.?2?Kinetic analysis of selective antimony removal by Na OH-Na₂S under ultrasonic condition:The kinetic analysis shows that both ultrasonic leaching and conventional leaching are controlled by surface chemical reaction.The dynamic equation is establishedConventional:1-?1-x?^1/3=5.97×10^-6·CNa OH^1.1·CNa2S^1.3·r0^-1·e^{-48390/8.314T}·t?4.8?Ultrasonic:1-?1-x?^1/3=6.69×10^-4·CNa OH^0.7·CNa2S^1.1·r0^-1·e^{-33880/8.314T}·t?4.9?Compared with conventional leaching,the reason why ultrasonic can increase the leaching rate of antimony is that ultrasonic can reduce the apparent activation energy,peel off the reaction layer,reduce the particle size,and reduce the concentration index and temperature of reactants.?3?Pretreatment of refractory gold ore with manganese anode slime sulfuric acid systemA new process of extracting gold and manganese from refractory gold ore by oxidation pretreatment and reduction leaching of manganese anode slime was developed.Response surface method was used to optimize the effects of time,temperature and sulfuric acid concentration on manganese leaching efficiency.When the ratio of the two ores is 1:0.5,the concentration of sulfuric acid is 1.25 mol/L,the temperature is 85?,and the leaching time is 2.5 h,the leaching efficiency of manganese is 91.64%.After pretreatment,the extraction efficiency of gold reaches90.30%,which is much higher than that of untreated ore.The improvement of gold leaching efficiency is attributed to the destruction of pyrite and the reduction of gold ore size.Therefore,the synergistic effect between the leaching of manganese anode slime and the oxidation pretreatment of gold concentrate not only realizes the leaching of manganese,but also improves the leaching efficiency of gold.