An Efficient Dealkalization of Red Mud Through Microwave Roasting and Water Leaching

How to obtain an efficient dealkalization process is a key issue for the resource treatment process of red mud. In this work, CaO was added to red mud and then mixed by ball milling after the mixture had been microwave roasted and water leached to achieve efficient dealkalization. The comparative investigation between the conventional roasting and microwave roasting-water leaching process was conducted. After that, the main factors and the mechanism of dealkalization of red mud under microwave roasting conditions were discussed. The results show that microwave roasting has better dealkalization efficiency and less energy consumption than conventional roasting under the same conditions. The dealkalization rate arrived at 84.04% under the optimum conditions, i.e., CaO/SiO2 molar ratio 2.4, microwave power 2.5 kW, roasting temperature 500°C, roasting time 45 min, liquid-solid ratio 8 mL/g, leaching temperature 90°C and leaching time 80 min. Ball milling promoted the mixing degree of red mud and CaO. The microwave roasting could effectively improve the crystal phase transformation of the alkali component in the red mud throughout the roasting process. The alkali metal component in the red mud was significantly extracted. The research can provide an idea for dealkalization and resource utilization of red mud.