Process And Mechanism Research On Sulfatizing Roasting Dealing With Two Stage Roasting Calcines Of Refractory Gold Ores

Abstract:Refractory gold ores make up two thirds of the gold resources all over the world. Two stage roasting is a traditional pre-treatment method dealing with the refractory gold ores, which has been broadly applied and has shown great adaptability, but fails to provide a higher gold leaching rate directly resulting more than lOg/t gold remaining in cyanide tailings. Fusion or recrystallized iron oxide particle, i.e. the hematite second-time wrap, mainly causes the above problem that prevents cyanide getting to gold, which thus remains in tailings. This research using sulfatizing roasting to deal with the calcines produced by two stage roasting, opened the hematite second-time wrap, therefore promoted gold leaching rate, and studied the mechanism during the process through cyanide tailing.Sulfatizing roasting dealing with the two stage roasting calcines shows a obviously reduction to gold content in cyanide tailings. The best process conditions are:sulfuric acid:water:calcine=1:1:1, i.e. sulfuric acid:100mL, distilled water:100mL, calcine:100g, drying under120℃and roasting3h under700℃. Under the above condition, the gold in cyanide tailing decreases from15.66g/t to2.2g/t.Through the sulfatizing roasting process, the phase changing of hematite, being as the main phase in raw material, has been fully studied. Tested by X-ray diffractometer, the whole course of the iron containing phase is known as bellow:Fe2O3â†'Fe4.67(SO4)6(OH)2·20H2O, HFe(SO4)2·4H2O, Fe2(SO4)3·5H2O(amorphous)â†'Fe2(SO4)3·5H2O (crystalline)â†'Fe2(SO4)3â†'Fe2O3.Following study of this process focusing on SEM and EDS of the calcines after sulfatizing roasting, further explained the mechanism of decreasing the gold content in cyanide tailing. The surface of the roasting calcine becoming more and more porous, which leads to more contact between gold and cyanide. The contrast between pre-and after-sulfatizing roasting picture of cross section of hematite and silicon dioxide show a 15%increase in specific surface area, indicating the correctness of the analysis.The study of thermal decomposition of ferric sulfate and equilibrium constant of SO3decomposition helps ascertain the reaction area. When temperature reaches about600℃, ferric sulfate and SO3both start to decompose, while it comes to ab-out700℃, the reaction goes downright, and at this time more SO3transforms to SO2, which consist of about30%of the overall sulfur.