Non-bayer-process red mud staged deep dealkalization method

The invention relates to a non-bayer-process red mud staged deep dealkalization method, and belongs to the technical field of resource integral utilization. The method mainly comprises the following steps that (1) red mud solid and water are prepared into suspension liquid according to a solid-liquid ratio being 1:1 to 1:15; the materials are stirred; CO2 is introduced to reach the saturation state, the temperature is room temperature to 50 DEG C, the pressure is normal pressure to 10bars, and the time is 30 to 1000 minutes; centrifugalization is performed; (2) red mud solids subjected to separation are uniformly mixed with extraction liquid containing unitary or/and polynary carboxylic acid as extraction agents according to the mass ratio being 1:1 to 1:10 to be prepared into suspension liquid; the suspension liquid is charged into a high-pressure reaction container; the materials are stirred; meanwhile, CO2 is introduced for deep dealkalization. The method has the advantages that the red mud is subjected to deep dealkalization in different stages, so that the strong alkalinity and the continuous alkalinity release characteristics of the red mud are weakened; the stable state using the insoluble carbonates as a main form is reached; the influence on the peripheral environment is greatly reduced.