Effects of Alkali-Treated Coal Fly Ash on Carbonation Efficiency and Its Implication for Carbon Mineralization
Purnaning Tuwuh Triwigati, Gyudae Sim, Dongju Seo, Youngjune Park
Abstract
The CO 2 storage capacity in coal fly ash (CFA) for carbon mineralization is often limited due to the dominance of the alumina-silicate phase on its particle surface. This study aims to enhance the carbonation efficiency by using the alkaline activator. H 2 O and NaOH solutions (1 and 3 M) were mixed with CFA with an L/S ratio of 0.15, respectively, and were carbonated using a direct gas–solid reaction. The highest carbonation efficiency was 43.57% for CFA-NaOH 3 M, while CFA-Raw had the lowest. With the NaOH addition, the binding energy shifted to a lower value for Si 2p and Al 2p in X-ray photoelectron spectroscopy (XPS) analysis and Si–O–Al bond was also shifted to a lower wavenumber in attenuated total reflectance Fourier-transform infrared (ATR FT-IR) analysis. Both analyses show how OH – ions affect the alumino-silicate bonds and disrupt their arrangement. X-ray diffraction (XRD) analysis revealed the appearance of Na–Ca–Si-hydrate, which turned into gaylussite (another carbonate form), which increased the amount of CO 2 stored in CFA.