CO2 Sequestration by Aqueous Red Mud Carbonation at Ambient Pressure and Temperature

An analysis of carbonation was carried Out with the aqueous fresh red mud Suspension at a liquid-to-solid ratio of 10 kg/kg, as well as in the leached-hydrated matrixes and leachates isolated from this red Mud suspension after three Successive leachings, to evaluate their intrinsic carbonation potential at ambient conditions (temperature of 20 +/- 1 degrees C and atmospheric pressure). The carbonation assays were performed at 20 degrees C using CO2 concentration of 15.00 vol% at a flow rate of 5 mL/min. The red mud matrix has a great leaching capacity of Na-(hydr)oxide, which is the principal hydroxide that seems to be implicated in the carbonation of leachates that have half-carbonation capacity of red Mud. Moreover, the carbonation of the red Mud suspension also involves a portlandite-containing matrix. The carbonation of the red mud Suspension and leachates implicates a complete neutralization of their content in Ca- and Na-(hydr)oxides. Although the leached hydrated-matrixes seem to be partially carbonated, it preserves a carbonation capacity near to that of leachate after three successive leachings. Moreover, three leached hydrated-matrixes and leachates have a carbonation capacity (7.09 g of CO2/100 of red mud) higher than the carbonation capacity obtained for the red mud suspension, which is evaluated to 4.15 g of CO2/100 g of red mud. Taken together, these results suggest that the carbonation of the red mud may be enhanced by the use of leached hydrated-matrixes and leachates obtained from multiple leaching.