| Zinc is an important nonferrous metal,which is second only to copper and aluminum in the consumption of nonferrous metals.Zinc metal has good ductility,wear resistance and corrosion resistance,and can be combined with a variety of metals to form alloys with better physical and chemical properties.For a long time,high-grade zinc ore has been exploited and utilized in large quantities,and the resources are gradually exhausted.How to exploit and utilize low-grade zinc ore effectively has been widely concerned and studied.In this thesis,the leaching and iron removal technology of low-grade mixed sulfide-oxide zinc ore from Lanping was studied.The leaching was divided into two stages:the zinc oxide in the first stage was leached.The influences of particle size,liquid-solid ratio,leaching pH value,temperature and reaction time on the zinc leaching rate were investigated.The second stage made full use of the leached iron ion,using SO2-Air as oxidant,SO2-Air-Fe(Ⅲ)coordination leaching of sulfide zinc.The ratio of m(NaHSO3)/Q(Air),leaching pH,leaching time,temperature and Fe3+ concentration on the influence of zinc leaching rate were studied.In the end,neutralization flocculation method was used to remove iron and silicon.The influences of pH value,temperature and reaction time on iron and silicon removal rates were investigated.The influence of ZnSO3·xH2O and its treatment were also discussed.The results are as follows:(1)Under the conditions of particle size less than 0.074 mm accounting for 77.55%,liquidsolid ratio 7:1(mL·g-1),pH=1.0,and temperature of 70℃,the zinc oxide ore in low-grade mixed sulfide-oxide zinc ore was generally leached for 2 h,and the total leaching rate reached 86.58%.(2)The optimal technological conditions of second-stage leaching:m(NaHSO3)/Q(Air)=0.021 g·L-1·min-1,pH=1.0,temperature 80℃,leaching time 2 h,the total leaching rate reached 95.32%.(3)The apparent activation energy of the first-stage leaching reaction of low-grade mixed sulfide-oxide zinc ore is 13.74 kJ·mol-1.The leaching rate is proportional to the concentration of reactants,and temperature has little influence on the leaching rate.The total leaching rate depends on the diffusion rate of reactants in the remaining dense layer.(4)Before neutralization,the oxidation of SO32-can be removed by air for 60 min,and the oxidation rate is above 96%.The ZnSO3·xH2O precipitation during the neutralization and flocculation process can be avoided,which would lead to zinc loss.(5)Fe2+ ion was oxidized by SO2-Air,then iron and silicon could be removed by neutralization flocculation.Under the conditions of temperature 70℃,terminal pH value 5.2 and neutralization reaction for 10 min.The removal rates of iron and silicon were 99.36%and 73.56%respectively,and the mass concentrations of liquid iron and silicon were 8 mg·L-1 and 75 mg·L-1 respectively. |
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