Extraction of iron and aluminum from high-iron bauxite by ammonium sulfate roasting and water leaching

High iron content is one of the challenges in utilizing the refractory bauxites in China. An improved method for treating the high-iron bauxite by roasting with (NH₄)₂SO₄ was proposed, which offers a possible alternative method for utilizing the high-iron bauxite. The influences of the roasting time, roasting temperature, material ratio, and ore particle size on the extraction ratios of Fe and Al were studied, and the orthogonal test was used to optimize the reaction conditions. The optimized reaction conditions were proposed as follows: roasting temperature of 450 °C, roasting time of 120 min, material ratio of (NH₄)₂SO₄ to ore of 2.5:1.0, and ore particle size below 80 μm. The roasting mechanism and kinetic parameters including the apparent activation energy and reaction rate constant were investigated. The results showed that the control step of the roasting process was the internal diffusion on the product layer and the apparent activation energy was 19.22 kJ mol⁻¹ in the reaction temperature range. The kinetic equation was obtained finally.