Abstract: Red mud is a strong basic solid waste residue discharged in alumina refinery industry.In order to reduce the alkali content of red mud and realize the comprehensive utilization of red mud，a preliminary comparison study on several de-alkalization processes，such as CO₂ extraction method, acid neutralization method，and Ca²⁺ replacement method was carried out.   Results showed that CO₂ extraction method could reduce pH of the red mud slurry and remove Na⁺ effectively; hydrochloric acid neutralization method was more effective for reducing pH of red mud slurry and through washing by water after acid neutralization，Na⁺ could be reduced substantially，but pH was increased；Ca²⁺ replacement method had a better effect on displacing combined alkali in red mud，but had little influence on pH.

Key words: red mud, de-alkalization process, CO₂, acid neutralization, Ca²⁺ replacement