Sequestration of CO2 by red mud with flue gas using response surface methodology

Energy demand is projected to increase throughout the globe in near future which necessitates the development of carbon capture and storage (CCS) technologies to avoid the harmful impacts of climate change. Direct mineral carbonation of alkaline solid wastes is one such technology that provides the benefit of being a permanent, cost effective and a promising on-site option, while improving the environmental quality of the waste. The present work attempts to study direct mineral carbonation of red mud (RM) with CO2 (concentration as in flue gas) by wet and dry route employing response surface methodology (RSM). Maximum reduction of about 18.5% in the concentration of CO2 was attained in wet carbonation conditions (65.1 oC, 42.1 bar, L/S ratio of 0.53, 1 h) and the sequestration capacity of RM was found to be 15.5 g of CO2/kg, correspondingly. The models were found to be statistically significant (R-2 value > 98.5%). Temperature and reaction time were found to influence the dry route. Meanwhile in wet route, temperature, pressure, liquid to solid (L/S) ratio and reaction time were all significant. The results demonstrated that RM could significantly sequester CO2 even from flue gas. The carbonation process was evidenced using Fourier-Transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM).