| There are abundant strategic rare-scattered metal resources in China's lead-zinc deposits,especially the zinc resources in Yunnan province which have large contents of indium(In),selenium(Se)and tellurium(Te),etc.Currently,about 80%of zinc is produced using the hydrometallurgy methods,which the main processes are roasting,leaching,purification and electrowinning.When the zinc concentrates are roasted,most of the rare-scattered metals remain in the zinc calcines,and then leach into the solution together with zinc during the sulfuric acid leaching process.As the acidity of the leaching solution decreases,most of the rare-scattered metals precipitate into the leaching residues for further enrichment and recovery,but some with low valence still remain in the leachate.Conventional zinc powder replacement or other methods cannot remove these impurities deeply.They are circulated and enriched in the zinc sulfate solutions,which will adversely affect the subsequent zinc electrowinning process,such as causing plate burning,hydrogen generation,and low current efficiency,etc.Therefore,it is necessary to deeply purify the rare'scattered metal impurities in the ZnSO4 solution in order to achieve the goals of zinc electrowinning process normally and improving current efficiencyAiming to solve the above problems,this paper carried out experimental study on the removals of rare-scattered metal impurities indium(In),selenium(Se)and tellurium(Te)from ZnSO4 solution by ultrasound'ozone combination,and the In kinetics at ozone and ultrasound-ozone combination were studied,respectively Conclusions are obtained as follows(1)Compared the results of parallel experiments under three conditions of ozone,ultrasound,and ultrasound-ozone combination,it can be concluded that the removal rates of In,Se and Te are higher in the condition of ultrasound-ozone combination than that in ozone and ultrasound,and the orders of the three methods to remove In,Se and Te are ultrasound-ozone combination>ozone>ultrasound,which shows the enhancement of ozone purification of above rare-scattered metals by ultrasound.(2)The ultrasound-ozone combination experiments are carried out to obtain the optimized process parameters to remove those rare-scattered metals in ZnSO4 solution.Under the optimized parameters,e.g.reaction temperature 60?,ozone flow rate 4.6 g/h,reaction time 10 min,and ultrasonic power 500 W,the removal rates of In,Se,and Te are 99.86%,99.26%and 98.94%,respectively,while the loss rates of Mn and Zn are 38.91%and 1.06%,respectively.The precipitate results show that the main phases are MnO2 and ZnSO4·H2O,which are in the form of irregular fine powder aggregates,and In,Se and Te are evenly distributed in the slag(3)The kinetic experiments of removal In from ZnSO4 solution by ozone,and ultrasound-ozone combination are carried out.The results show that the apparent activation energy of ozone and ultrasound-ozone conditions are Ea1=13.09 KJ/mol and Ea2=12.62 KJ/mol,respectively.The introduction of ultrasound helps to reduce the activation energy of the reactions,and the reactions are more affected by the ozone diffusion.The macro kinetic models under ozone and ultrasound-ozone combination are as followsOzone:Kobs1=3.08 × 103 exp(-1574.91T)C[H+j-0.133 C[In]-0.644 Q[O3]0.303 C[Mn]0.135[ST]0.0211 Ultrasound-ozone combinationKobs2=4.32 × 103 exp(-1517.40T)C[H+]-0.144 C[In]-0.610 Q[O3]0.268 C[Mn]0.107[US]0.130... |
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