Study On The Effect Of Gold Concentrate Roasting Pretreatment On Silver Leaching

In order to achieve comprehensive recovery of resources,it is currently widely used in China to add sodium salt-based additives to improve the leaching effect of associated metal silver in refractory gold mines,but there have not systematically studied for the roasting products of different minerals under the action of additives and their dissolution characteristics in the subsequent leaching process.In response to these problems,this study selected two gold concentrates LB and LN with different ore compositions to compare the silver leaching effects.Through actual mineral condition tests,thermodynamic calculations,pure mineral TG-DSC tests and SEM surface detection analysis,not only obtained the optimal roasting-acid leaching-cyanide leaching process conditions for each of the two gold concentrates,and made the different oxidation and leaching behaviors clear in the roasting,acid leaching and cyanide leaching stages after the different associated minerals react with additives.Thereby perfect and enrich the interaction system between additives and refractory gold ore oxidative roast-acid leaching-cyanide leaching.In the process of raw ore analysis,it was found that the mineral composition of LB type ore was simple,the sulfide minerals were mainly pyrite and chalcopyrite,the main gangue minerals were quartz,and the content of metal elements Au,Ag and Cu were2.51g/t,866g/t and 2.60% respectively.While the mineral composition of LN type ore was complex,there were many gangue mineral types,and the content of metal elements Au,Ag and Cu were 41.71g/t,575.83g/t and 0.26% respectively.The experimental results of process exploration showed that the content of Cu in LB type ore was high,so LB type ore was suitable to adopt the traditional roast-acid leaching-cyanidation leaching process for copper bearing gold concentrate.The content of Cu in LN type ore was low,so it was not significant to recover copper by acid leaching,but it was found that the cyanide leaching rate of Au can be significantly improved after acid leaching from the experimental results,so the two kinds of gold concentrate finally decided to use the process of roast-acid leaching-cyanide leaching.The roasting orthogonal test determined the significance of the roasting temperature and the type of additives on the leaching rate of Au,Ag,Cu of LB and LN type ores.The two kinds of ores were tested by the comprehensive conditions of roasting-acid leaching-cyanide leaching.The final cyanide leaching rates of Au,Ag and Cu of LB type ore under the premise of using sodium sulfite as additives were 86.55%,83.53% and 95.65%,respectively.Compared with the roastingacid leaching-cyanide leaching without adding sodium salt,the leaching rates of gold,silver and copper were increased by 15.82%,1.44% and 16.83% respectively.While the LN-type ores were roasted by adding sodium hydroxide and the leaching rates of Au,Ag,Cu reached 93.92%,64.35% and 78.65%,compared with roasting-acid leaching-cyanide leaching process without adding sodium salt which were increased by 4.67%,10.00% and17.33%,respectively.According to TG-DSC thermal analysis and SEM analysis,through the thermodynamic calculation of the roasting and leaching process,the roasting and leaching behaviors of pure minerals pyrite,chalcopyrite,sphalerite,quartz,dolomite and pure silver minerals in different proportions was studied,found that when the gangue mineral quartz exists during the roasting process,the free energy of quartz reacting with chalcopyrite,pyrite and sphalerite and other metal sulfides to form silicate materials is much lower than the free energy of the metal sulfide itself redox.The silicate materials will adsorb and wrap with the silver oxide and form a large-size object.It is stable in the cyanide leaching residue,resulting in a low silver leaching rate.Adding sodium sulfite or sodium hydroxide can promote the conversion of sulfide metal to metal oxide and reduce the formation of silicate minerals,therefore improve silver leaching effect;When dolomite is present in the mineral,its effect for the leaching rate of silver was direct,silver minerals will be directly adsorbed on the surface of dolomite and its decomposition and acid leaching products,which makes silver leaching difficult.However,the function of sodium salt is dissimilar in adsorbing and desorbing sulfide ores,dolomite and silver minerals at different temperatures.When the roasting temperature is lower than 600℃,the sodium salt will weaken the mutual adsorption between the sulfide minerals,dolomite and silver mines,the silver leaching rate is improved;In addition to the types of additives and mineral types that affect the silver leaching rate,elemental silver minerals have a reduction under high temperature conditions.It can directly convert sulfide ore into low oxide or simple substance to reduce the generation of silicate and dense oxide,and then improve the leaching rate of silver mineral itself.The effect of roasting pretreatment on silver leaching has been studied.The results showed that the different associated mineral components in gold concentrate have different effects on silver leaching effects.Different additives and roasting temperature range will directly affect silver leaching results.How to improve silver leaching results still needs to select appropriate additives according to the types of associated minerals in the raw materials.The related research results can provide certain theoretical support and practical guidance for the production of the same type of mining enterprises.