Iron Removal And Gold Leaching Technology From The Calcine Of High Iron, Sulfur And Arsenic Gold Concertrate

Gold leaching rate of calcine, roasted from high-sulfur and arsenic gold concertrate, is frequently some low for new capsule to gold by iron-bearing minerals. For example, some calcine, produced by a gold smelter in Hunan, contains Fe of31.25%and Au of84.27g/t,in which wrapped gold occupys more than10g/t. Residual gold of the calcine after common leaching is up to14.53g/t.Aim at the phenomenon that iron oxides wrap gold in calcine, several methods to deal with it respectively to improve gold leaching rate are adopted, namely Deironing by acid-dissolution, Reducing-roasting and acid-dissolution and Sulfuric acid curing and leaching process. This may bring guiding significance to gold extraction to similar gold ores.Gold leaching rate of calcine only reaches80.50%if cyanides directly. Deironing by acid-dissolution dissolves little irons for the bad acid-soluble of hematite, so the capsuled structure cannot be broken sufficiently, leading a slight improvement of gold leaching rate, and12%of Au is residual even a mechanical activation has been taken during leaching process.Reducing-roasting and acid-dissolution converts hematite to metallic iron, which dissolves easily in acid solution. The removal of iron breakdowns wrapped structure of gold and brings a gold leaching rate of above90%. But there is still7-10percents of gold leaves behind for a new package by ferric metasilicate formed during reducing-roasting process and for some fine particle metallic iron hardly dissolved is harmful to the extraction of gold.During Sulfuric acid curing and leaching process, hematite reacts with sulfuric acid and water and transforms to rhomboclase (HFe(SO4)2·4H2O), which dissolves in water while leaching. The formation of rhomboclase acquires a higher iron removal rate and breakdowns wrapped structure more thoroughly so gold leaching rate can been improved sharply. And the higher iron removal rate, the more gold can been leached. For example, when reduces the iron content to below 7.5%, gold leaching rate is above97%.A higher sulfuric acid concentration promotes iron removal, while a overtop concentration means the lack of water, which results in the waste of H2SO4and hinders diffusion, leading a lower iron removal rate. A reasonably higher tempreture lowers the Gibbs Free Energy and enhance seepage force of H2SO4, and more iron can be removed. Increasing sulfuric excess coefficient and curing time is benefit to the removal of iron as also. The proper conditions acquired by experiments are as follows:sulfuric concentration75%, sulfuric excess coefficient1.4, curing temperature250℃and curing time1h, under which the iron content of calcine is reduced to below7.5%,87.37%of wrapped gold can be exposed and the gold leaching rate is above97%.