Formation And Transformation Of Iron Slag During Iron Removal By Hematite Method

The environmental problems of waste disposal are becoming more and more prominent in traditional hydrometallurgical industry.Compared with jarosite and goethite residues,hematite has the potential to become a by-product sold to steelmaking,cement manufacturing and coatings industry due to its high iron content.And ultimately realize the utilization of iron resources.Sulfur content is one of the important factors that affect the quality of hematite and its resource utilization.At the basis of sulfate solution bearing high iron,the present paper mainly focused on the transformation of metastable phase(jarosite)to hematite in hematite process.Listed below are the main results.(1)The effects of temperature,time,Na2S04 concentration,seed crystal concentration and initial acid concentration on the hematite process,metastable phase transition and S adsorption and transformation behavior were investigated in FeSO4-Na2SO4-H2O system.The experimental results show that increasing the temperature,prolonging the reaction time and decreasing the concentration of the initial acid,and controlling the concentration of Na2SO4 not only can improve the iron removal efficiency,but also can effectively inhibit the formation of jarosite and promote it transformation into hematite,reduce the chemisorption of sulfate in the iron residues.The presence of seed crystals can effectively reduce the supersaturation of Fe3+ in the solution,reduce the content of jarosite in the iron residues,and the hematite precipitate with smooth and dense surface,uniform size and stable nature was obtained.High quality hematite with Fe,S and Na content of 65.8%,1.42%and 0.067%,respectively,iron removal efficiency of 96%were obtained when the temperature was 180 ?,time 3 h,oxygen partial pressure 0.4 MPa,seed addition of 15 g/L and the concentration of sodium sulfate was 0.15 mol/L.(2)The effects of reaction temperature,zinc sulfate concentration,reaction time and ferrous ion concentration on the hematite process and transition behavior of metastable were investigated in FeSO4-Na2SO4-ZnSO4-H2O system.The experimental results show that the excessive zinc sulfate concentration in the hematite process leads to the deterioration of the crystallinity of the hematite crystal and its stability.And the content of Fe in residueswas reduced while Zn and S were increased.Furthermore,Excessive sulfate concentration also affects the amount of oxygen dissolved and ion migration velocityin the solution,resulting in a large amount of Fe2+ not being oxidized inpurified solution,thereby reducing the iron removal rate.The initial ferrous concentration has a significant effect on the morphology of iron precipitate.The high concentration of ferrous iron can cause the crystal form of hematite to be deteriorated and the crystal grains are dispersed in an amorphous shape.(3)The iron removal efficiency is larger than 95%at temperature of 190 ?,seed addition of 15 g/L,time of 3h and oxygen partial pressure of 0.4 MPa,zinc ion concentration was 100 g/L,Na2SO4 was 15 g/L.Iron content of precipitate was larger than 60%.S,Na content was 1.42%and 0.067%,respectively.The hematite was only phase in residuce.