Density Functional Theory Study On The Surface Properties Of Chalcopyrite And The Adsorption Of Cn-on Its Surface

Intensely inhibited by cyanide,the chalcopyrite contained in the cyanide taillings have not been recycled effectively in china,which resulted in the problems of waste of resources and environment pollution.At present,the level of comprehensive utilization of copper resources in cyanide tailings was low,and the researches on the mechanism of cyanide inhibition of chalcopyrite were inadequate,bringing troubles to the recovery of this part of copper resources.Through the first principle method based on dnesity functional theory,this paper studied the surface properties of chalcopyrite and the adsorption of CN^-systematically.In addition,the first principle simulation results were verified through the single mineral flotation tests and X ray photoelectron analysis.The dnesity functional theory calculation results showed that,the chalcopyrite is a kind of direct band gap simicondunctor,the ration of Fe and Cu valence was closed to 3:1,and the stability of S-Fe bond in chalcopyrite was higher than that of S-Cu bond.After surface relaxation,the obvious suface reconstruction occured on the surface of?0 0 1?-M,?0 0 1?-S,?1 1 2?-M,?1 1 2?-S and?1 1-2?-M,and only the surface of?1 1-2?-S underwent a slight surface relaxation.The production of S₂^2- and S_n^2- and the enrichment of S element were occurred on the surface of chalcopyrite due to the reconstruction of surface slab models,making the chalcopyrite exhibit good natural floatability.With high thermodynamic stability,the surface of?1 1 2?-M was the most stable cleaved facet of chalcopyrite,since the surface energy of?1 1 2?-M was the lowest.The CN^- could adsorb on the?1 1 2?-M surface of chalcopyrite easily,and the Fe-Fe hollow site was the most preferred with the adsorption energy of-304.69 kJ/mol.The CN^-adsorption via the C atom bonded with Fe atom on the surface.The 2s orbital of C interacted with the 4s and 4p orbitals of Fe,forming a covalent s bond.The 3d orbital of Fe donated electrons to the antibonding 2p orbital of C to form the d-p back donating p bond.The single mineral flotation results indicated that,with low concentration of sodium cyanide,the effect of sodium cyanide on chalcopyrite flotation was little,while the concentration of sodium cyanide reached 0.8%,the recovery rate of chalcopyrite fell below 20%.The inhibition effect was strong,which were consistent with the theoretical calculation of CN^-adsorpting on chalcopyrite surface.With the leaching time expanded,the recovery of chalcopyrite increased slightly,which was mainly due to the disdolution of Cu²⁺,consuming a part of cyanide and producing a certain activation on chalcopyrite.XPS analysis results demonstrated that,the valence configuration was Cu⁺Fe³⁺(S^2-)₂.The existence S₂^2- of S_n^2- on the surface of chalcopyrite was consisitent with the first principle calculation results.After the adsorption of cyanide,the relative contents of O element on the surface were reduced greatly,indicating that the adsorption of cyanide hindered the reaction of oxygen molecules with mineral surface.Sodium cyanide can form the hydrophilic substance of iron cyanide complexes and cyanocuprate on the chalcopyrite surface,exerting inhibitory action.Sodiun cyanide was preferentially associated with Fe atoms,which can interacted with Cu atoms when the concentration of sodium cyanide was high.