Hydrotalcites and zeolites are materials characterised by a high capacity for CO₂ adsorption and can therefore be useful adsorbents for the capture of CO₂ 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 CO₂ 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 CO₂ 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 CO₂ physisorption properties and was therefore the most suitable candidate for low temperature and pressure swing adsorption generally required in short-term CO₂ 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 CO₂. The findings demonstrated the suitability of utilising HT_FA for both short- and long-term capture of CO₂.

水滑石和沸石是具有高CO ₂吸附能力的材料，因此可以用作从烟道气中捕获CO _2的有用吸附剂。在这项研究中，成功地从南非燃煤飞灰中合成了两种沸石（NaX _FA和NaA _FA）。在我们以前的工作中，对它们的CO ₂吸附特性以及由相同粉煤灰合成的水滑石（HT _FA）的特性进行了研究和比较。此外，本文报道的CO ₂的新的分级形态的NaX型沸石的吸附容量（NaX的_FA）由粉煤灰制成。这种材料的特征是板状结构排列成球状簇，晶体宽度在63 nm至99 nm之间。NaX _FA具有很高的CO ₂物理吸附特性，因此是短期和短期CO ₂吸附应用中通常需要的低温和变压吸附的最合适的候选物。相反，对于NaA _FA和HT _FA均观察到了物理吸附和化学吸附特性。然而，HT _FA是最适合化学吸附CO _2的材料。研究结果证明了使用高温超导_FA的适宜性用于短期和长期捕获CO ₂。