Non-cyanide Leaching Agent-ammonium Thiocyanate Gold Leaching Process And Mechanism

The possession of gold is a strong representative of a country.Traditionally,gold has mainly used cyanide leaching and extraction processes.Due to the high toxicity of cyanide,it has serious harm to the environment and organisms.Therefore,the study of new types of cyanide extraction and recovery of gold has become a domestic Urgent problems to be solved.In this paper,the leaching of refractory gold ore after biological pretreatment was carried out,and ammonium thiocyanate was used to conduct the gold leaching experiment.The results are as follows:Mineralogy studies have shown that the refractory gold ore contains high levels of arsenic and sulfur,so it is pretreated with biological oxidation.The main gangue mineral in the ore is pyrite,and contains toxic sand and chalcopyrite;the non-metallic minerals are mainly quartz and silicate minerals.After biological oxidation,most of the natural gold has been dissociated or exposed.The theoretical leaching rate of gold cyanide is 86.83%;most of the unexposed natural gold is wrapped by sulfides?pyrite and arsenic-containing pyrite?.The grains are very fine,most of which are less than10?m.Some secondary products form a secondary coating on natural gold,mainly gypsum,potash,etc.If the secondary coating is not considered,the theoretical leaching rate of gold is 92.73%.On the basis of conditional test research,the best conditions for ammonium cyanate gold leaching are:sulfuric acid to adjust pH2,liquid to solid ratio 3:1,oxidant20g/L,ammonium thiocyanate 40g/L,leaching stirring speed 400r/min After stirring for 4 hours,the gold leaching rate was 93.60%.Through the design expert8.0 software,the quadratic multivariate linear equation regression fitting of the three-factor three-level ammonium thiocyanate gold leaching process is used to obtain the ammonium thiocyanate concentration?A?,oxidant concentration?B?and solution pH?C?.Response surface optimization obtained the best process parameters consistent with the conditional optimization test.Thermodynamic studies have shown that the oxidant in the gold leaching system of ammonium thiocyanate mainly oxidizes Au to Au³⁺,and then forms a complex ion Au?SCN?₄^-with the thiocyanate;Oxidative decomposition,so the acidic leaching process is adopted.The smaller the pH of the solution,the more it can promote the gold leaching reaction of ammonium thiocyanate.The leaching kinetics study shows that under the best leaching conditions,the simulation shows that the leaching process is controlled by chemical reaction,the apparent activation energy Ea is 43.46kJ/mol,the pre-finger factor is 11.33,and the oxidant reaction order is 0.8 The reaction grade of the leaching agent is 1.1.