Absorption of CO2 in a bubble column using red mud

Abstract In the industrial production of aluminum through the Bayer process, two main pollutants are generated, red mud and carbon dioxide (CO2). Conventional processes for treating polluting waste include the neutralization of red mud with hydrochloric acid (HCl) and the capture of CO2 with ethanolamine (CH2(NH2)CH2OH). However, the CO2 generated can be used to neutralize the red mud, allowing the simultaneous treatment of two harmful substances and reducing the amount of HCl required to neutralize the red mud. The solvent present in red mud is the residual alkaline liquor from the Bayer process, which absorbs CO2 in a secondary stage, but is not yet considered as a pollutant treatment process. From this perspective, the treatment of two polluting substances (red mud and CO2) can be carried out in aluminum production plants with lower energy consumption. In the present study, bench and pilot-scale tests were carried out to verify the efficiency of CO2 adsorption by red mud at a temperature of 25 °C. Among the results of bench tests, 84.05% CO2 absorption by red mud was obtained. And on a pilot scale, using a bubble column and continuous flow, an efficiency of 96.80% CO2 absorption was observed with red mud. The study also found that among the most significant variables in this type of treatment are the solid content and mechanical speed.