Journal of CO2 Utilization

Hydrotalcites and zeolites are materials characterised by a high capacity for CO 2 adsorption and can therefore be useful adsorbents for the capture of CO 2 from flue gases. In this study, two types of zeolites (NaX FA and NaA FA ) were successfully synthesised from South African coal combustion fly ash. Their CO 2 adsorption properties, as well as those of a hydrotalcite (HT FA ) synthesized from the same fly ash in our previous work, were investigated and compared. In addition, this paper reports the CO 2 adsorption capacity of a novel hierarchical morphology NaX-type zeolite (NaX FA ) made from fly ash. This material was characterized by plate-like structures arranged in ball-like clusters with crystal widths of between 63 nm and 99 nm. NaX FA was characterised by very high CO 2 physisorption properties and was therefore the most suitable candidate for low temperature and pressure swing adsorption generally required in short-term CO 2 adsorption applications. In contrast, both physisorption and chemisorption properties were observed for NaA FA and HT FA . However, HT FA was the most suitable material for chemisorption of CO 2 . The findings demonstrated the suitability of utilising HT FA for both short- and long-term capture of CO 2 .

Synthesis, characterisation and CO2 adsorption potential of NaA and NaX zeolites and hydrotalcite obtained from the same coal fly ash