Study On Leaching Mechanism Of Gold From Tailings By Ultrasonic Coupled Ozone

With the continuous mining of gold resources,the reserve resource of high-grade and easy-to-concentrate gold ore continues to decrease,and the proportion of refractory gold ore and gold tailings continues to increase.As a result,more attention has been paid to the loss of gold in the process of leaching and smelting,extraction and recovery of the remaining gold in tailings has become a new research hotspot.As of late,various techniques have been used on gold leaching from tailings involing flotation process,chlorination process and biological oxidation method,etc.However,these methods have some drawbacks and limitations,in view of the alarming situation,the current study used ozone as oxidant,with the joint action of ultrasonic to leach gold from tailings,and demystify the influence of different conditions of gold leaching from tailings mechanism.The main research contents and results of this study are as follows:(1)By comparing the effects of single ultrasonic action,single ozone action and ultrasonic coupled ozone oxidation on gold leaching,it is found that the combined action of ultrasonic and ozone on gold leaching from tailings is better than that of single ozone and single ultrasonic leaching,and the range of the gold leaching rate of ultrasonic coupling ozone oxidation is 22%?45%.The orthogonal experiment results showed that after adding ozone catalyst,the best leaching effect was achieved when the ozone flux was 5 g·h-1,the temperature was 40?,the leaching time was 3 h,the solid-liquid ratio was 120/5 mL·g-1,the ultrasonic intensity was 0.32 W·cm-2,and the mass of ozone catalyst was 6 g,and the leaching rate reached to 54.19%.The orthogonal experiment results showed that the main factors affecting oxidizing gold leaching are liquid-solid ratio;temperature;time;ozone catalyst mass;ultrasonic power.In order to further improve the leaching rate,based on the orthogonal test,the gold leaching rate can reach to 88.61%with addition of thiourea under the conditions of ozone flux of 5 g·h-1,liquid-solid ratio of 120/5 mL·g-1,ultrasonic intensity of 0.32 W/cm2,temperature of 60?,time of 3 h,ozone catalyst mass of 6 g,and thiourea concentration of 10 g/L.(2)The SEM,BET,LPS,XPS,XRD and XRF were used to characterize the tailings before and after the reaction,and the mechanism of ultrasonic coupling ozone leaching was studied.SEM results showed that after the reaction,the tailings have more fine flaky structures,more fluffy and porous.The tailings after the reaction have obvious etching marks than before.The LPS results showed that the overall particle size of the tailings after the reaction is slightly smaller than that before the reaction,with little change.The BET results showed that the specific surface area of the tailings after the reaction is 6.4 times larger than that before the reaction,and the pore volume is 6.06 times larger than that before the reaction.Combined with the SEM results and the BET results,it can be seen that there are more voids inside the tailings particles after the reaction.Under the oxidation of ozone,the gangue opens the gold wrapping.The XRD results showed that the diffraction peak intensity of the tailings after the reaction decreases as compared with that before the reaction,which indicated that the mineral crystallinity decreases after the gold leaching reaction.The phenomenon is beneficial to gold leaching.The gold leaching process was fitted under the optimum experimental conditions,and the leaching process was controlled by an interfacial chemical reaction.The gold leaching process is mainly controlled by interfacial chemical reaction.(3)Using the experimental data obtained in the process of gold leaching,the artificial neural network model was used to simulate the process of ultrasonic coupled ozone oxidation leaching,and the gold leaching rate was predicted.The back-propagation neural network model of "7-14-1" error with 14 nodes in a single hidden layer(BP neural network model)is established by using MATLAB software.Through the analysis and calculation of the model,the mean square error of the obtained test data is only 0.0013,and the slope and correlation coefficient after linear fitting of the predicted value of BP neural network model and the training experimental values are 0.9 and 0.956 respectively,indicating a high degree of fitting.Neural network prediction and verification of the comparison results between the experimental results show that the slope and the correlation coefficient were 0.92 and 0.945 respectively,the linear fitting degree is higher indicates the prediction of the model is more reliable.The comparison of the predicted values and the actual value results showed that the built by artificial neural network model can make an effective simulation of the reaction process.The model of the same type of gold tailings in other areas can also have good prediction accuracy.