Research On The Comprehensive Utilization Of Valuable Metals In Gold Smelting Slag

With the rapid development of China’s gold industry and high gold production, the problem of the gold smelting slag treatment has become more and more serious in recent years. Stockpiling of gold smelting slag occupied the large areas of arable land, resulting in a waste of valuable land resources, but also poses a great threat to the surrounding environment of the mines. Meanwhile, there are still some gold, silver, copper, lead, zinc, iron and other valuable metals in the gold smelting slag, which has a significant recycling value. So far there is still no efficient way to recover the valuable metals from it. Consequently, the research on the comprehensive utilization of valuable metals in gold smelting slag has a great practical significance, whice can not only relieve environmental problems caused by the stockpiling of mine solid waste and improve the comprehensive utilization of minerals, but also create considerable economic benefits to the mine enterprise.The research object of the gold smelting slag was produced by a gold smelter in Henan province which is the tailings produced by the process of acidification roasting, acid leaching and cyanide leaching of gold and silver from sulphide ore flotation gold concentrate. Different pertinence experiment route was designed based on the study of process mineralogy. The comprehensive recovery of gold, silver, copper, lead, zinc, iron from gold smelting slag was conducted by magnetizing roasting-magnetic separation process, reducing roasting-magnetic separation process, acid leaching-slag cyanide leaching process, chloridizing roasting process, and two-stage roasting process, which obtain a more satisfactory test indicators for the next step to expand the process to provide technical reference.The appearance of gold smelting slag is reddish brown, and the mineral particle size is very fine. Furthermore, the mud phenomenon is serious, while the mineral composition is complex. The largest component is hematite, and the main gangue minerals are quartz, feldspar, gypsum, and talc. Gold and silver are wrapped in hematite and gangue minerals, which is the main reason causing the hard leaching of gold and silver.According to the magnetizing roasting-magnetic separation test, the optimum technological conditions are as follow:the gold smelting slag was roasted at 780 ℃ for 60 minutes with coal consumption 4%, and then ground it to -0.045mm accounted for 93.23%, with magnetic field intensity 120KA/m. Under the conditions, the total iron grade of iron concentrate was 55.63% and the total iron recovery was 80.31%. The flash roasting minerals was adopted as the raw material and the test procedure was optimized based on the analysis of magnetic separation concentrate. After three stage grinding, single-stage roughing, five-stage cleaning, the total iron grade of magnetic separation concentrate reached 61.74%, and iron recovery rate of 66.98%.According to the reducing roasting-magnetic separation test, the optimum technological conditions are as follow:the gold smelting slag was roasted at 1150℃ for 60 minutes with coal consumption 13%, and then ground it to -0.045mm accounted for 74.55%, with magnetic field intensity 60KA/m. Under the conditions, the total iron grade of iron concentrate was 93.21% and the total iron recovery was 82.72%.According to the acid leaching-slag cyanide leaching test, the optimum technological conditions are as follow:with sulphuric acid as acid leaching solution, the concentration of sulfuric acid is 60%, acid leaching temperature 90℃, leaching liquid to solid ratio was 2.5:1, leaching time was 2h. Under these conditions, the iron leaching rate can reach 91.4% and the leaching rate of gold and silver was 72.8% and 62.4%. The iron oxide product with Fe2O3≥93% could be produced by ammonium precipitation, and the iron recovery rate is more than 85%.According to the chloridizing roasting test, the optimum technological conditions are as follow: with 7% CaCl2 as chlorination agent, under the roasting temperature of 1100℃, and roasting time 60 minutes, the volatilization rate of gold, silver, copper, lead, zinc in gold smelting slag were 96.01%,81.69%,86.57%,99.67%,99.07%.Two-stage roasting process was brought out firstly on the basis of chloridizing roasting test. With coking coal as reducing agent into chloridizing roasting sample, the total iron grade of iron concentrate was 92.99% and the total iron recovery was 83.34% which realized the comprehensive recovery and utilization of valuable metals in gold smelting slag.Research shows that the comprehensive utilization of gold smelting slag has certain feasibility, and it will be of great value to industrial test.