Phase Transformation Behavior of the Aluminosilicate Phase During High-Pressure Hydrothermal Reduction of High-Iron Red Mud

One-step separation and recovery of sodium, aluminum and iron in high-iron red mud in a high-calcium alkaline hydrothermal system is realized by a high-pressure hydrothermal reduction process. The transformation behavior of the aluminasilica phase in high-iron red mud is mainly investigated. The results show that under the optimized conditions, a temperature of 290℃, a Na₂O concentration of 240 g/L, a calcium to silicon ratio of 3.5, and a liquid–solid ratio of 5, the Na₂O content in the transition slag is reduced to 0.12%, the dealkalization rate can reach 98%, and the alumina dissolution rate is 73%. When the starch-free reductant is added, the transition slag mainly consists of hematite and hydroandradite, and when the starch reductant is added (the addition amount is 1/4 that of ω(Fe₂O₃) in the red mud), all Fe₂O₃ in the transition slag is completely reduced to Fe₃O₄, and the main phases are magnetite and hydrogrossular.