Study On Reutilization Of Iron Tailings For Stepwise Extraction Of Iron And Silicon

To solve the problem of resource utilization of iron tailings in China,based on the research of the basic properties of iron tailings,the Fe2O3 of iron tailings were reduced to Fe3O4 by the mixture reducing gas composed of CO,H2,CO2 and N2,suspension magnetization roasting.Through magnetic separation,iron concentrates and silicon rich magnetic separation slags were obtained.Subsequently,the silicon rich magnetic separation slags were used to prepare nano-Si O2 by alkali melting silicon extraction and ultrasonic precipitation.Therefore,to obtain iron concentrate and nano-Si O2,a technical route of utilizing suspension magnetization roasting magnetic separation-alkali melting-ultrasonic precipitation to recycle iron tailings was established.In the research of the basic properties of iron tailings,the chemical composition,phase composition and micro morphology of iron tailings were analyzed through the chemical analysis and instrumental analysis.The main elements in iron tailings(expressed in oxide form)are Fe2O3 and Si O2,and iron grade is 43.71%.Iron phase exists ?-Fe2O3: ?-Fe O(OH): (?)-Fe O(OH)= 2.025: 1: 1.285.Iron tailings show angular massive structure with compact texture,and most of the particles are in the range of 300-4000 ?m.In the stage of obtaining iron concentrate products by suspension magnetization roasting and magnetic separation,the effect of gas volume,magnetic field,particle size,temperature,time and the proportion of H2 and CO on iron grade and recovery ratio was investigated.The optimal iron grade of 62.06% and recovery ratio of 98.03% was obtained via suspension magnetized roasted-magnetic separation at 500 m L·min-1,120-80-60 m T magnetic field,40% over 200 mesh,600 ?,10 min and H2: CO: CO2: N2 = 20: 15: 15: 50.For magnetization roasting,H2 is equivalent to H2 and CO mixture but much better than CO.Suspension magnetization roasting can effectively convert hematite and goethite in iron tailings into magnetite,increase the saturation magnetization from 0.77 Am2·kg-1 to 59.43Am2·kg-1,and magnetic separation can effectively separate magnetite and quartz.After suspension magnetization roasting,the BET surface area of iron tailings increases from8.1226 m2·g-1 to 21.2902 m2·g-1 and the microstructure of iron tailings is loose,cracked and porous,which can save energy consumption for subsequent grinding and beneficiation.In the stage of preparing nano-SiO2 by ultrasonic precipitation after alkali melting from high silicon magnetic separation slag,the effects of temperature,Na OH / magnetic separation slag ratio and time on the silicon extraction ratio were focused of the alkali melting;The effects of the addition amount of PEG 1000,dissolved water and p H on the yield and specific surface area of nano-Si O2 were focused of the preparing nano-Si O2 by ultrasonic precipitation.The optimal silicon extraction ratio of 94.63%,nano-Si O2 yield of2.1731 g(4.0000 g magnetic separation slag)and specific surface area of 123.0209 m2·g-1was obtained via alkali melting at 325 ?,Na OH / magnetic separation slag ratio of 1.5 and25 min,while ultrasonic precipitation at 3 wt.% PEG 1000,the dissolved water volume /magnetic separation slag of 20 m L·g-1 and p H 8.The insoluble Si O2 is transformed into miscible Na2 Si O3 by alkali melting.The average Si O2 content of nano-Si O2 reaches 90.47%.Nano Si O2 are nano materials with particle size less than 50 nm and spherical branches,with an average pore diameter of 14.1361 nm.Taking the recovery of iron and silicon by suspension magnetization roasting magnetic separation-alkali melting-ultrasonic precipitation method as the technical core,the utilization of iron tailings resources can not only solve the problems of environmental pollution and resource waste of iron tailings,but also obtain iron concentrate and nano Si O2 with market value.The project research has important scientific value and practical application significance for the recycling of iron tailings.