Research On A New Process Of Zinc Leaching From Zinc-containing Metallurgical Slag Dus

As an important strategic resource,zinc is the key construction material to the national defense,the support material to the development of high technology and the foundation material of national economy,has important strategic position in the national economy and national defense construction.However,china’s first fourteen consecutive years of zinc consumption in the world,there are some issues such as zinc mineral resources shortage,low grade,complicated composition and so on,which cause the zinc metal supply shortage become more and more serious,and self-sufficiency is less than 80%.Meanwhile,with the rapid development of steel industry and zinc metallurgy industry,zinc metallurgical slag and dust(MSD)with high contents of alkaline gangue and associated with polymetallic mineral was stockpiled,and the zinc contents in which exceeds one million tons.The recycle value of zinc in MSD becomes increasingly important,and an important way can be provided to ease the shortage of non-ferrous metal zinc resources.Zinc mainly exists in the form of zinc oxide,zinc iron spinel,zinc silicate and zinc sulfide in MSD,meanwhile,with high alkaline gangue,high fluorine chlorine content(Cl was 12%,and the highest F of up to 2%)are its characteristics.One result is that the F and Cl can dissolve into the leaching liquid by conventional acid leaching technology,and another result is that high zinc recovery rate will consume large acid,lead to a large number of ferric sulfate and silicic acid dissolved into the leaching liquid.The conventional acid leaching process promotes silica gel formation and complicates the subsequent purification process.To solve this problem that zinc in MSD is very difficult to leaching by conventional acid leaching technology,a new method is proposed by microwave activation pretreatmentultrasonic enhanced ammonia collaborative coordination leaching zinc MSD in this paper.Using a series of conditional experiments,dynamic analysis and response surface optimization methods to research the leaching zinc mechanism research from MSD.To further reveal the microwave activation pretreatment-ultrasonic strengthening leaching mechanism of cooperative coordination,the solid liquid phase compositions,phase,morphology are characterized with laser particle size analysis,XRD,SEM,EDS,FT-IR and ESI-MS analytical means.The main research conclusions are as follows:Based on existing ammonia leaching and alkali leaching process matching body(NH3,Cl-,OH-)limitations,to a certain extent restricts the development of selective leaching system.Comparative study the different ammonium salt system on the zinc leaching rate of blast furnace,it was found that the addition of CH3COONH4 to NH3-H2O system promotes the extraction of zinc.At the same time,the comparative study the leaching process on blast furnace dust and MSD in NH3-CH3COONH4-H2O system was conducted.The results show that the reaction apparent activation energy on blast furnace dust and MSD are much the same,and which of them are 22.32 and 22.66 kJ/mol,respectively.Further illustrate NH3-CH3COONH4-H2O system are universal for zinc secondary resources recycling.The leaching process is controlled by the diffusion and interface transfer.Compare with the phase and morphology structure of samples before and after leaching by XRD and SEM-EDS,it is found that zinc silicate(Zn2SiO4),zinc sulfide(ZnS)administered and zinc ferrite(ZnFe2O4)is the low zinc leaching rate of the main restrictive factors in zinc metallurgical slag dust.The Fourier Transform Infrared Spectroscopy(FT-IR)and Mass spectrometric(MS)analysis showed that,adding CH3COONH4 as leaching agent,zinc can combine with the NH3-CH3COONH4 coordination to form[Zn(Ac)(NH3)i]+ and[Zn2(Ac)3(NH3)2]+ complex ions,to further promote the dissolution of zinc.In order to achieve the transformation from refractory zinc mineralogical phase to easy handle zinc oxide phase,the microwave calcium-activation pretreatment zinc metallurgical slag dust is studied.The results showed that microwave calcification pretreatment can achieve conversion from difficult to deal with mineral zinc silicate and zinc ferrite into zinc oxide,and the ZnS diffraction peak administered decreased significantly by XRD and SEM-EDS characterization analysis.The grade of the ore leaching phase is improved,promote the leaching of zinc.On the other hand,based on the absorption wave characteristic differences of useful minerals and gangue potter cause,lead to many multiphase complex ore system temperature is uneven distribution on the microstructure,strengthen the useful mineral dissociation and produce cracks,increasing the useful mineral interface reaction area,accelerate the diffusion rate,to further strengthen the leaching reaction process.Under the condition of the conventional leaching optimization process parameters,control microwave activation temperature 400℃,CaO content 25%,activation time 20 min,the zinc leaching rate of zinc MSD is 91.67%,zinc leaching rate increased by 3.9%compared with the same conventional roasting process,and zinc leaching rate increased by 7.4%compared with the conventional optimization(84.27%)of the leaching process.The ultrasonic-microwave pretreatment strengthen leaching kinetic study indicates that the leaching process is controlled by the diffusion and interface transfer,and the corresponding activation energy is 8.23 kJ/mol.The initial activation energy is low compared with the conventional leaching zinc MSD.The parameters of zinc leaching rate from MSD are optimized by Response surface model,and the zinc leaching rate are 94.05%,and zinc leaching rate increased by about 10%compared with the conventional optimization(84.27%)of the leaching process.Compare with the phase and morphology structure of samples before and after leaching by XRD,SEM-EDS and laser particle size analysis,it is found that ultrasound can exfoliation the inclusions exist in particle interior and surface,and elaboration particle formation "2E effect".At the same time,strengthen the coordination leaching of zinc oxide ore samples,shorten the leaching reaction time,improve the zinc leaching rate.In summary,aiming at the shortcomings of the existing processing MSD by conventional method of recovery of zinc,put forward a new technology of microwave activation pretreatment-ultrasonic enhanced ammonia collaborative coordination leaching zinc MSD.In conclusion,an effective way is provided for the clean utilization of those zinc unconventional resource and for reference the development of new technology.