The Interaction Between Sphalerite And Pyrite And Its Influence Mechanism On The Separation Of Zinc-sulfur Flotation

High pyrite-bearing lead-zinc deposits are common and abundant in China,such as Huize lead-zinc mine,Yilang lead-zinc mine,Lancang lead-zinc mine in Yunnan Province and Fankou lead-zinc mine in Guangdong Province.However,except for the finely disseminated textures,the interactions between minerals and grinding medium are also an important factor affecting the selective flotation of galena and sphalerite due to the high content of pyrite in the ores.Taking Yilang lead-zinc mine of Yunnan Province for example,as the rare and enriched lead-zinc deposit,the ore contains 51.75%FeS2 and the total content of sulfide minerals in ores is more than 85%.Nevertheless,the high reagents consumption and the low zinc grade in concentrates are still existed in commercial operation due to the effect of pyrite on selective flotation of galena and sphalerite.Therefore,the interaction between sphalerite and pyrite was choose as the research object.Firstly,the interaction between sphalerite and pyrite in flotation and its effect on the flotation behavior of mineral,surface characteristics and reagent adsorption were investigated by micro-flotation,electrochemical measurement,XPS surface analysis and DFT calculation.The mechanism of interaction between sphalerite and pyrite was explained from macroscopic and microscopic viewpoint.Based on these studies,the feasibility of Zn grade improvement in concentrates by intensifing or weakening the interaction between sphalerite and pyrite was also investigated.The results from micro-flotation indicated that the interaction between sphalerite and pyrite in pulp have a detrimental effect on the selective separation of sphalerite from pyrite.With absence of collector in pulp,the recovery of sphalerite at pH ranges of 7.3 to 11 and the flotation rate of sphalerite at pH=10 were respectively decreased,but the recovery and flotation rate of pyrite is oppositely increased in this pH ranges.With presence of collector butyl xanthates in pulp,the recovery of sphalerite at pH ranges of 4.0 to 11 and the flotation rate of sphalerite at pH=10 are also decreased due to the interaction between sphalerite and pyrite,while the recovery of pyrite at pH ranges of 9.0 to 12 and the flotation rate of pyrite at pH=10.0 are increased.With the presence of activator CuSO4 and butyl xanthates,the recovery of sphalerite at pH range of 4.0 to 12 and the flotation rate of sphalerite at pH=10.0 are identically decreased dueto this interaction,but the recovery of pyrite is increased at pH ranges of 4.0 to 7.3 and decreased at pH ranges of 9.5 to 12.On the other hand,the influence magnitude of interaction between sphalerite and pyrite on flotation behavior is closely related with the ratio of sphalerite and pyrite in pulp.The results from dissolution tests indicated that the dissolution amounts of Zn2+from sphalerite surface was significantly increased when the presence of pyrite in pulp,and the dissolution amounts of Znri is 80 times higher than that in pulp with the absence of pyrite.The dissolved Zn2+ can adsorb on sphalerite and pyrite surface in the formation of Zn2+ or Zn-hydroxy complex,and the zeta potential of sphalerite and pyrite surface was altered.In addition,the surface oxidation of sphalerite was promotedand the hydrophobic oxidation products S0was formed on sphalerite surface due to the interaction between sphalerite and pyrite,but the adsorption of metal-hydroxy complex on sphalerite surface was also improved.Adsorption measurement of Cu2+ and butyl xanthates showed that the adsorption amounts of Cu2+ on sphalerite surface was reduced because of interaction between sphalerite and pyrite.The proportion of Cu(?)-S activation products on sphalerite surface was significantly decreased,which causes the decrease of copper activation efficiency on sphalerite surface.For pyrite,the adsorption of Cu2+ on pyrite surface was promoted due to the interaction between sphalerite and pyrite,and relative copper atomic concentratrion on pyrite surface is increased from 0.79%to 1.29%after interaction.However,without the presence of copper sulfate in pulp,the adsorption amount of butyl xanthates on pyrite was weaken.Electrochemical measurements demonstrated that the corrosion rate of sphalerite was increased when sphalerite is electrochemically contacting with pyrite,but the oxidation current density of pyrite was decreased at low scanning potential ranges.These results indicated that the surface oxidation of sphalerite was enhanced when contacting electrochemically with pyrite,and the surface oxidation of pyrite was oppositely inhibited.On the other hand,the oxidation current density of butyl xanthates to dixanthogen on pyrite surface was decreased due to the electrochemical contacting with sphalerite,which reduces the adsorption of butyl xanthates on pyrite surface.DFT calculation showed thatwhen sphalerite surface contacting with pyrite surface,Zn 4s orbits lose a lager amounts of electrons and S 3p orbits lose a small number of electrons on sphalerite surface.For pyrite surface,Fe 4s and 4p states obtain electrons,S 3p orbits lose a small fraction of electrons.The electron transfer from sphalerite to pyrite will occur when the sphalerite is in contact with pyrite,the transferring electron numbers is decreased with the increasing distance between sphalerite and pyrite surface.The surface oxidation of sphalerite is intensified due to the contacting with pyrite and losing electrons,but pyrite surface oxidation is alleviated due to receive the electron from sphalerite surface.In addition,the transfer ability of electrons between sphalerite and pyrite surface was improved with the presence of H2O.Besides,the adsorption of Cu2+ was weaken due to the presence of pyrite in copper activation of sphalerite.The flotation tests of Yilang lead-zinc ores of Yunnan Province indicated thatchanging the addition position of collector from conditioning stage to grinding mill is helpful for the improvement of pyrite recovery,which weaken the detrimental effect of interaction between sphalerite and pyrite on the adsorption of xanthates collector on pyrite surface.Besides,the detrimental effect of pyrite on copper activation of sphalerite was weaken due to the reduction of pyrite content during sphalerite flotation.On the other hand,the increase of pulp pH in Zn roughing is beneficial to improve the grade of Zn concentrates and weaken to the interaction between sphalerite and pyrite.The results of closed-circuit flotation demonstrated that the grade of Zn concentrates is increased from 48?49%to 55.43%,and the recovery of Zn is uniform with industrial practice.But the consumption of flotation reagents is less than industrial practice.