Study On Enrichment Process Of Iron In Ammonium Jarosite Residue

Ammonium jarosite[(NH4)2Fe6(SO4)4(OH)12]residue is a waste residue derived from iron removal process of ZnSO4 solution.In addition to(NH4)2Fe6(SO4)4(OH)12,the jarosite residue contains SiO2,In,Zn,Cu and Ag.The objectives of this study were to eliminate envelmental pollution caused by accumulation of the jarosite residue on land and to recover valuable metals Fe from the residue.Decompasition-transformation and iron enrichment process of ammonium jarosite residue were investigated and study contents included four steps:(1)In ammonia solution,(NH4)2Fe6(SO4)4(OH)12 was decomposed to amorphous iron oxide(Fe2O3�xH2O)and(NH4)2SO4;(2)In ammonia solution,FeSO4 and Fe2O3�xH2O were transformated to Fe3O4 and(NH4)2SO4;(3)Fe3O4 was separated from SiO2 by magnetic separation technology;(4)Regenerated ammonia water was obtained from(NH4)2SO4 solution by CaSO4 precipitation method with Ca(OH)2 as precipitator.Experimental results showed that:(1)The optimum conditions for the decomposition of ammonium jarosite residue were shown as follows:ammonium jarosite residue of 100g,ammonia water of 50 mL,liquid/solid ratio of 3:1.temperature of 70?,stirring speed of 200r/min,and reaction time of 30 min.Under this condition,the decomposition rate was 99.22%,and the iron content of the decomposed solid product was 48.25%.(2)The decomposed solid product was used as a raw material for the conversion reaction,the optimum conditions for the conversion of ammonium jarosite residue were shown as follows:ammonia water of 50 mL,the Fe3+ in the residue and the Fe2+ in the FeSO4 were in a molar ratio of n(Fe3+)/n(Fe2+)=2:1,liquid/solid ratio of 5:1,temperature of 60?,stirring speed of 200 r/min,time of 30 min.Under these conditions,the converted solid product was the ferroferric oxide slag,its iron content was 56.32%.(3)Iron and silicon in ferroferric oxide slag were separated by two-stage magnetic separation.The best process conditions for the first stage of magnetic separation were shown as follows:time of 20 min,liquid/solid ratio of 15:1 and magnetic field strength of 80mT.Under these conditions,the concentrate yield,concentrate iron grade,and concentrate iron recovery were 77.86%.60.42%and 79.85%,respectively.The optimal magnetic field strength of the two-stage magnetic separation is 90 mT.Under these conditions,the concentrate yield,concentrate iron grade,and concentrate iron recovery were 80.32%,62.54%and 92.35%,respectively.(4)The optimal experimental conditions for the utilization of ammonium sulfate solution were shown as follows:ammonium sulfate solution of 600mL(300mL of each solution after decomposition and after conversion),stirring speed of 200 r/min,temperature of 25?,calcium oxide of 40 g,time of 20 min.Under this condition,CaSO4�2H2O precipitate and regenerated ammonia water were obtained.Regenerated ammonia water was used for the decomposition of ammonium jarosite residue,and the decomposition effect was better.However,the alkali concentration needs to be further improved.