Reaction behavior of silicon-rich diasporic bauxite with ammonium sulfate during roasting

Abstract

The separation of Al from the silicon-rich diasporic bauxite is of great significance in alumina production. Herein, we proposed a low-temperature ammonium sulfate roasting-water leaching process to extract aluminum from silicon-rich diasporic bauxite. Parameters including roasting temperature, dosage of ammonium sulfate, roasting time, and particle size of ore were investigated. Under the condition of roasting temperature of 400 °C, roasting time of 5 h, ammonium sulfate dosage of 2.5 times of the theoretical value and ore particle size of 80–96 µm, more than 98% leaching rate of aluminum was obtained. The phase transformation and mechanism during the roasting process were revealed by using X-ray diffraction, thermogravimetric analysis, differential thermal analysis, and scanning electron microscope methods. The diaspore and kaolinite phases in the silicon-rich diasporic bauxite could react with ammonium sulfate to form corresponding sulfates (NH₄)₃Al(SO₄)₃, NH₄Al(SO₄)₂ and Al₂(SO₄)₃. The proposed technology could provide an effective method for the direct and separation of aluminum from silicon-rich diasporic bauxite.

Keywords

silicon-rich diasporic bauxite / ammonium sulfate / roasting / separation

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