Control of Carbon Dioxide Sequestration by Mechanical Activation of Red Mud

Mineral carbonation is a potentially attractive sequestration technology for the permanent safe disposal and immobilization of CO2. In this technology, CO2 is chemically reacted with calcium, sodium, and magnesium containing materials to form thermodynamically stable and environmentally harmless minerals, usually carbonates. In our research, mechanical activation of red mud was carried out in order to enhance its reactivity by means of mechanochemical reactions (surface activation), and its sequestration behaviour was investigated using carbon dioxide gas at 25 °C temperature and at high pressure (5 bar) in an autoclave. The reacted red mud was characterized by Fourier-transformed infrared spectrometer, scanning electron microscopy, X-ray diffraction, laser particle size analyzer, BET specific surface area measurement, and pH measurement. It was found that mechanical activation improved the CO2 sequestration ability by 1.7 wt% of red mud, as demonstrated by the above investigations. The pH of red mud slurry can be lowered by reacting it with carbon dioxide. During our measurements, the pH of the suspension decreased from 10 to 6.81. Furthermore, the carbonation process can be successfully used to decrease the amount of harmful PM10 (particles with a diameter of 10 μm or less) and PM2.5 (particles with a diameter of 2.5 μm or less) fraction. The proportion of 10 μm particles can be reduced by 40% and that of 2.5 μm by 20%. Graphic Abstract