Abstract:

Red mud is an alkaline solid waste released from Al₂O₃ smelting and can be used as capture agent to absorb CO₂ in fume.In this paper, red mud from Bayer process of China Aluminum Corporation was selected and used, and the effect of reaction temperature, time, and ratio of solid to liquid, agitation speed and CO₂ flow rate on absorbing efficiency of red mud was investigated to obtain the best process parameters and conditions.The results show that one gram fluidic red mud containing 44.12%（mass） water can capture 0.11—0.12 g CO₂ at 40℃, under the ratio of solid to liquid of 1∶10, the reaction time of 120 min, the agitation speed of 700 r·min^-1 and the CO₂ gas flow rate of 0.25 L·min^-1.The properties of red mud before and after absorbing CO₂ were characterized by XRD, SEM, BET, and FT-IR.The data from XRD show that main components of red mud are Ca₂SiO₄, CaCO₃,Na₂Si₂O₅, CaTiO₃, Ca₃Si₂O₅, Ca₃Al₂O₆, and NaCO₃, after the reaction with CO₂, the peaks of Ca₂SiO₄, Na₂Si₂O₅ and Na₂CO₃ in XRD pattern disappear.Furthermore, owing to the alkaline substances in red mud can react with CO₂ to get carbonates；some new phases can be found in the XRD spectrum.The analysis by SEM, BET and FT-IR imply that the microstructures and shapes of red mud have occurred a change and are different before and after capturing CO₂.These data results show that red mud can be used for capturing CO₂ in fume and provide an effective way with low cost for reducing carbon emissions.