Research On The Technology And Mechanism Of Comprehensive Recovery Of Silver, Zinc And Iron By Zinc Leaching Slag Beneficiation And Smeltin

Zinc leaching residue,as a kind of hazardous waste with large yield and complex properties,is stored for a long time,which not only occupies a large amount of land resources,but also the heavy metal elements in the residue will flow into the ecosystem,causing harm to the natural ecological environment.In the zinc leaching residue produced by conventional leaching method,there are many kinds of valuable metals,among which the recovery value of silver,zinc and iron is relatively higher.The silver in zinc leaching residue coexists with zinc sulfide,while the iron mainly combines with zinc to form zinc ferrite.In order to realize the resource treatment and comprehensive utilization of zinc leaching residue,avoid the discharge of waste residue and pollute the environment.In this study,the conventional zinc leaching residue from a zinc smelter in Yunnan was taken as the research object,and combined with the properties and composition of zinc leaching residue,a combined process of“flotation-magnetization roasting-leaching-magnetic separation”was proposed to treat zinc leaching residue.On the basis of conditional tests,by means of X-ray diffraction analysis,electron probe microanalysis,vibrating sample magnetometer analysis and other analysis and testing techniques,the optimum test parameters of flotation silver recovery test of zinc leaching residue and the magnetization roasting mechanism of zinc leaching residue were systematically studied.In this paper,the effects of grinding fineness,activator and collector on the flotation effect of silver in zinc leaching residue were investigated through flotation roughing test,and the optimum process parameters were determined.On this basis,the open-circuit flotation test was carried out,and the best closed-circuit flotation process was developed.Closed-circuit flotation test obtained silver concentrateⅠwith silver grade of 3448.00 g/t and silver recovery of 53.10%and silver concentrateⅡwith silver grade of 1545.60 g/t and silver recovery of 15.65%.Considering the comprehensive silver recovery,concentrate I and concentrate II were combined.The silver grade of the combined concentrate was 2693.42 g/t with a silver recovery of 68.75%.Zinc ferrite magnetization process that zinc ferrite is reduced to zinc oxide and ferric oxide process.The thermodynamics of zinc ferrite magnetization roasting process was studied in depth by Factsage 8.2 software,and the magnetization decomposition process,equilibrium product composition,advantage interval and so on were calculated.It was found that zinc ferrite could be reduced and decomposed by a small amount of elemental carbon when the temperature was higher than 500℃,and the increase of carbon dosage and temperature could promote the reduction and decomposition of zinc ferrite,even over reduction.In the reduction and decomposition process,Zn is continuously presented in the form of Zn O,while iron oxide is continuously reduced as Fe₃O₄-Fe O-Fe.On the basis of thermodynamic calculation,a single factor roasting experiment was carried out.The soluble zinc rate,ferrous rate and saturation magnetization were used to investigate the effects of reducing agent dosage,roasting temperature and roasting time on the magnetization roasting effect of flotation tailings.It was found that the reducing agent dosage had the greatest effect on the roasting effect,and too high temperature and too long time may lead to the formation of solid solution of zinc and iron.The optimum process parameters were determined.Under the optimum conditions,the soluble zinc rate in the slag was 88.52%,the ferrous rate was 52.47%,and the saturation magnetization intensity was 26.09 emu/g.The magnetization decomposition of zinc ferrite was realized.The effects of leaching acidity,temperature,time,liquid-solid ratio and stirring speed on the separation of zinc and iron from magnetized decomposition slag were investigated by single factor low acid leaching test,and the optimum process parameters were determined.Under the optimum conditions,the leaching rate of zinc and iron reached 64.49%and 32.50%respectively.The low intensity magnetic separation of the secondary leach residue at the magnetic field intensity of 3560 Oe showed that the recovery rate of iron in the magnetic concentrate was 57.47%and the grade of iron was more than 45%.The test and analysis results of the combined process of“flotation-magnetization roasting-low acid leaching-magnetic separation”show that the combined process can realize the comprehensive utilization of silver,zinc and iron in zinc leaching residue.