Research On The Solid-sulfur Roasting And Thiosulfate Gold Leaching Technology Of A Gold Concentrate

Refractory gold ores rich in arsenic and sulfur will produce sulfur dioxide and other harmful substances when they are roasted and oxidized,which will cause serious air pollution if they are directly discharged.Cyanide leaching is the most traditional gold leaching process,but it is also a harmful gold extraction process to the environment.Therefore,it is of great significance to explore a non-polluting roasting process suitable for specific gold concentrate and a non-toxic and non-polluting leaching method suitable for this kind of baking sand.In this paper,calcium salt,sodium salt and magnesium salt were added in the process of calcination oxidation in order to solidify harmful substances,and then gold was extracted from the calcined sand in the copper-ammonia-thiosulfate system,so as to reduce the pollution to the environment.In this regard,gold concentrate was pretreated by solidification roasting,and the effects of solidification agent types,solidification agent dosage,roasting temperature and roasting time on the effect of sulfur solidification were investigated.The leaching rate of gold and the solidification effect of harmful substances of gold concentrate after roasting were compared comprehensively to determine the conditions of solidification roasting suitable for gold concentrate.The results showed that the calcium-based solidification reagent had a better sulfur dioxide effect on sulfur dioxide.Among them,?Ca?OH?₂?has the best effect.When Ca/S is 1.0-1.5,the roasting temperature is 650? and the roasting time is 3 h,the solidification efficiency of sulfur in gold concentrate can reach 84.67%.The calcined sand obtained after the solidification roasting process is suitable for the copper-ammonia-thiosulfate leaching system,in which the leaching rate of gold in the cu-ammonia-thiosulfate system can reach 90% after the calcium-based solidification pretreatment.X-ray diffraction?XRD?,scanning electron microscopy?SEM?and BET specific surface area test showed that the pyrite and arsenopyrite in gold concentrate were oxidized to hematite and calcium sulfate after pretreatment by solidification roasting,this process also results in the decomposition of the sulfide inclusions surrounding the gold,and the formation of more pores on the surface of the gold concentrate,so that the gold can have more interfacial reactivity points to contact with the leaching solution,thus improving the leaching rate of gold.X-ray photoelectron spectroscopy?XPS? showed that arsenic and sulfur from arsenopyrite in gold concentrate were oxidized to stable arsenite and sulfate respectively during the pretreatment process of solidification roasting.