| As the aluminum industry of our country has entered a rapid development period,the application of aluminum runs into a much wider field.Due to China is a country which relatively lack aluminum resources,the high-grade mineral resources are scarcer.Therefore,it is meaningful to carry out comprehensive utilization of low-grade bauxite.The small particles of aluminum and iron minerals in the bauxite mingles together.Besides,the valuable mineral is hard to separate.Therefore,the study on the effective separation of low-grade high-iron bauxites has a very important practical significance.In the thesis,the ammonium sulfate fusion-dissolution method was taken to separate silicon and iron.Then,in order to separate aluminum and iron,chemical coprecipitation-alkaline leaching method was taken to dispose aluminum and iron coexist dissolution liquid.Finally,phosphate dissolution-ammonium hydroxide control pH precipitation method was taken to prepare iron phosphate.The conclusions are as follow:(1)When fusing temperature was 300℃,fusing time was 4h and the ratio of ammonium sulfate-to-high iron bauxite was 6:1,the extraction rate of Al was 92.1%and the extraction rate of Fe was more than 93.5%without silicon.(2)Silicon slag consists of silica,titanium dioxide and a small amount of alumina.(3)The optimum conditions of co-precipitation were obtained:reaction temperature was 60℃,reaction time was 60min,and the pH value of the solution was 5.0.The extraction rate of Al was 97.6%and the extraction rate of Fe was 97.9%.(4)The optimum conditions of alkali leaching was obtained:reaction temperature was 90 ℃,reaction time was 60min.The dissolution rate was 91.3%.(5)In the Fe3+ and phosphate coexist solution(Fe3+:phosphate=1:6),the pH value was controlled by phosphate.When the pH value was 2,the white precipitates were mainly(NH4)Fe(HPO4)2·2H2O.When the pH value was 5,the white precipitates was in Amorphous type.The product roasted at 500℃ for 7h was in Amorphous type.The product at 550℃ was hexagonal type FePO4.The product at 600℃ was FePO4 in good crystalline state. |
