Study On The Alkaline Elution And Enhanced Leaching Process Of Zinc Oxide Dust And Fluorine And Chlorin

Zinc oxide dust is obtained by fuming and volatilizing zinc-containing solid waste produced in the smelting process of iron and steel plants.In addition to zinc,lead,indium,but also fluorine,chlorine and other harmful elements.This paper draws on the detection method of fluorine occurrence in coal ash : step by step chemical extraction method method is analyzed the fluorine occurrence state in zinc oxide dust,and then the alkali washing experiment is carried out.According to the extraction experiment results,the reason of low alkali washing removal efficiency is analyzed.In the leaching part,a combined leaching technology of oxidation leaching-pressure leaching is proposed for the zinc oxide dust after alkali washing.The combined leaching and oxidation neutralization and iron removal are combined into one step,and then the leaching residue is subjected to pressure acid leaching under the condition of no oxygen.Using the oxiadtion of ferric iron to dissolve sulfide,the leaching efficiency of zinc and indium is improved,and the valuable metals such as lead are effectively enriched.The research contents and results are as follows :(1)The phase and morphology of unalkali washed bag zinc oxide dust,boiler zinc oxide dust and mixed zinc oxide dust are analyzed.It can be seen that the unalkali washed zinc oxide dust contains zinc oxide and zinc sulfide phases.The two kinds of zinc oxide dust also contain lead sulfide and other phases.The morphology of bag zinc oxide dust is mostly irregular flake surface adhered to fine particles.The morphology of boiler zinc oxide dust is mostly slender needle and irregular polygonal flake structure.The fluorine content of bag zinc oxide dust,boiler oxide dust and two mixed zinc oxide dust is 0.51%,1.75%,0.64%,0.96%,and the chlorine content is 6.67%,4.7%,9.82%,5.47%,respectively.The phase of zinc oxide dust after alkali washing is mainly zinc oxide and zinc hydroxide,and also contains a small amount of zinc sulfide.The morphology is mainly loose small particles and agglomerated large particles with small particles adhered to the surface.The zinc content is 53.2%,the iron content is5.33%,the lead content is 6.28%,and the indium content is 452.3 g/t.(2)The step-by-step chemical extraction tests of bag and boiler zinc oxide dust are carried out.The ion exchangeable fluorine in bag zinc oxide dust accounted for the most(54%～57%),and the residual fluorine in boiler zinc oxide dust accounted for the most(56%～64%).Four kinds of zinc oxide dust are treated by alkali washing.When sodium carbonate and sodium hydroxide mixed solution,salt solution,sodium carbonate and sodium hydroxide pure solution are used as alkali washing solution,the fluorine removal efficiency of zinc oxide dust in boiler is the lowest.Combined with the results of chemical extraction tests,the fluorine removal efficiency of bagged zinc oxide dust is about 80%.Combined with the proportion of fluorine occurrence,ion exchangeable,carbonate bound and organic bound fluorine can be removed by alkali washing.The removal efficiency of fluorine in zinc oxide dust of boiler is only 20%.Combined with the proportion of fluorine occurrence,the residual,iron and manganese oxide bound fluorine can not be removed by alkali washing.(3)The effects of neutralization time,hydrogen peroxide dosage and oxygen time on the leaching of mixed zinc oxide dust after alkali washing are studied.The results show that the zinc leaching efficiency is 82.32% and the iron content in the leaching solution is 3.88 mg/L when the reaction temperature is 60 °C,the leaching time is 2 h,the neutralization time is 2 h,the amount of hydrogen peroxide is 62.0 m L/kg and the liquid-solid ratio is 3.9 m L/g.The lead phase in the leaching residue is lead sulfate,the zinc phase is zinc sulfide,and the morphology is mainly agglomerated or dispersed block particles.The leaching residue efficiency is 83%,containing zinc 18.43%,iron10.51%,lead 13.42%,and indium 863.2 g/t.The pressure leaching of the leaching residue is carried out,and the sulfide is oxidized by the ferric iron in the leaching residue.When the reaction temperature is 125 °C,the time is 3 h,and the liquid-solid ratio is 2.5 m L/g,the total recovery efficiency of zinc is 98.62%,and the recovery efficiency of indium is 90.48%.The leaching residue efficiency is 65%,containing0.83% zinc,2% iron,30.48% lead and 267.4 g/t indium.The main phase is lead sulfate,and lead is effectively enriched.The concentration of trivalent iron ion in the highpressure leaching solution is low,which can be sent to the indium recovery process.