Direct C[O.sub.2] sequestration onto alkaline modified oil shale fly ash

The present study focuses on the direct chemical adsorption of C[O.sub.2] onto alkaline hydrothermally activated oil shale fly ash (OSFA). The C[O.sub.2] chemisorption experiments were conducted in a high-pressure reactor at a temperature of 150°C and C[O.sub.2] 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 29Si 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 C[O.sub.2], 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 C[O.sub.2] from flue gases. Keywords: tobermorites, direct C[O.sub.2] sequestration, oil shale fly ash.