Direct CO2 sequestration onto alkaline modified oil shale fly ash

The present study focuses on the direct chemical adsorption of CO2 onto alkaline hydrothermally activated oil shale fly ash (OSFA). The CO2 chemisorption experiments were conducted in a high-pressure reactor at a temperature of 150 degrees C and CO2 partial pressure of 100 bar during a 24-hour period. Original, activated and chemisorbed OSFA samples were characterized by means of X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) coupled with energy-dispersive X-ray spectroscopy (EDS), specific surface area (BETN2) and high-resolution Si-29 magic angle spinning nuclear magnetic resonance (MAS-NMR). The results indicated moderate weight increase (max 5 wt%) and according to XRD and MAS-NMR analysis tobermorites had reacted with CO2, leading to calcite formation. The results also show that the alkaline hydrothermally activated OSFA has a potential to be used in industrial processes for direct chemical adsorption of CO2 from flue gases.