Process for recovering sodium carbonate and magnetic iron oxide from red mud by using carbon dioxide

The invention relates to the technical field of red mud treatment, in particular to a process for recovering sodium carbonate and magnetic iron oxide from red mud by using carbon dioxide, which comprises the following steps: 1) mixing the red mud, filtrate and washing water according to a certain proportion, pulping and grinding to obtain red mud slurry; 2) introducing carbon dioxide into the red mud slurry, adjusting the pH value to 8-9, and carrying out filter pressing to obtain a solid and a filtrate; (3) concentrating part of the filtrate in the step (2) to obtain a concentrated sodium carbonate solution, and performing multi-effect evaporation on the sodium carbonate solution to obtain sodium carbonate; (4) washing the solid obtained in the step (2) for multiple times, pulping, performing magnetic separation, and drying a magnetic separation substance to obtain magnetic iron oxide; according to the method, the red mud is treated with carbon dioxide, sodium carbonate can be recycled, meanwhile, magnetic i