The Mechanism Of Oxidation And Decomposition Of Chalcopyrite Influenced By Complex And Multiple Factors In Mine Environment

As an important copper resource,chalcopyrite exists widely in mine environment.Understanding the chalcopyrite oxidation process is of great significance for promoting the industrial application of hydrometallurgy and alleviating the environmental problems caused by mine wastes.The surface layer formed during chalcopyrite oxidation is considered to be the main cause of passivation,but the dissolution mechanism of chalcopyrite and the specific composition of the product layer are still unclear.The oxidation of chalcopyrite is a complex reaction process that involving the gas-liquid-solid phases,and many factors may affect the dissolution of chalcopyrite.To explore the chalcopyrite oxidation mechanism under the influence of different factors,and to analyze the composition of chalcopyrite surface layer,so as to regulate the oxidation process of chalcopyrite more effectively.The natural oxidation of mineral,the coexisting of sulfide minerals with silver ions,the residual of flotation agents on mineral surface,and pre-treat process of mechanical activation are the common and inevitable factors in chalcopyrite mine environment.Therefore,this paper explores the influence of these factors on chalcopyrite oxidation.The main research contents and conclusions are as follows:（1）The evolution of elemental valence states on chalcopyrite surface under atmospheric oxidation condition was investigated.The results showed that the surface energy of fresh chalcopyrite surface was mainly contributed by the conductive surface and the accumulated negative charge surface.Sulfur mainly existed in the form of S^2-and was quickly reconstructed to form S₂^2-and S_n^2-.Besides,copper and iron existed in the form of Cu⁺and Fe³⁺,respectively.With the increase of atmospheric oxidation time,the surface of chalcopyrite showed an insulating state.The content of S^2-decreased and SO₄^2-was gradually formed.The oxidation state of Cu did not change,while Fe would quickly form Fe-O or Fe-O-OH substances.（2）The leaching mechanism of chalcopyrite with sodium persulfate-sulfuric acid under the action of silver ion was investigated.The results showed that silver ion can accelerate the leaching of chalcopyrite with sodium persulfate-sulfuric acid.The presence of silver ion can promote the conversion of chalcopyrite to chalcocite which is more prone to dissolve.At the same time,Ag⁰ or/and Ag₂S were also formed on chalcopyrite surface.Fe²⁺released by chalcopyrite dissolution can activate persulfate and accelerate the generation of sulfate radical.Therefore,the leaching efficiency of chalcopyrite was improved.（3）The effect of pyrite on bioleaching of chalcopyrite after mechanical activation was investigated.The results showed that mechanical activation significantly improved the promotion effect of pyrite on chalcopyrite bioleaching.The mechanical activation significantly reduced the particle size of the minerals,and increased the specific surface area and surface energy of the minerals.The galvanic effect between chalcopyrite and pyrite was strengthened after activation,and the pyrite could maintain the solution potential within the optimal range.Thus,the leaching of chalcopyrite was improved.（4）The bio-dissolution mechanism of chalcopyrite promoted by pyrite and silver ions was investigated.It was found that Ag⁺reduced the formation of passivation substance S_n^2-/S⁰.The H⁺and Fe³⁺released by pyrite dissolution could react with silver intermediates to regenerate silver ions and provide oxidant Fe³⁺for chalcopyrite dissolution.Since silver ion and pyrite are inevitable associated with chalcopyrite,the combined effect of them on chalcopyrite bio-oxidation will intensify the release of copper ion and acid.（5）Potassium amyl xanthate（KAX）was selected as the representative flotation collector to explore the effects of flotation agents on chalcopyrite bio-dissolution.The results showed that KAX accelerated the bio-oxidation process of chalcopyrite.KAX reduced the adsorption of microorganisms on mineral surface,making more microorganisms being free,therefore the regeneration of oxidant Fe³⁺was accelerated.Also,KAX reduced the formation of passivation substance S_n^2-/S⁰ and the surface tension of solution,which was conducive to the diffusion of oxidants Fe³⁺to chalcopyrite,and finally promoted the bio-oxidation of chalcopyrite and increased the formation of acid mine drainage.