Adsorption Capacity Enhancement on Coal Fly Ash for Carbon Capture in Humid Flue Gas: A Critical Review

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Adsorption-based carbon capture has emerged as a pivotal sustainable technology for realizing the vision of carbon neutrality owing to its low energy consumption and structurally straightforward design. However, the low adsorption capacity and high preparation costs of adsorbents have hindered scalable industrial applications. Recent studies have demonstrated the feasibility of preparing carbon dioxide adsorbents from industrial waste for the scalable capture of carbon dioxide in humid flue gas. In this review, we focus on the utilization of coal fly ash from coal-fired power plants to fabricate adsorbents with high adsorption capacity and low cost for use in humid flue gases. We review the progress in various carbon dioxide adsorption materials derived from fly ash including metal oxides, zeolites, silica aerogels, and amine-based composite adsorbents. We envision that the preparation strategy for fly ash-derived adsorbents with high adsorption capacity will yield increasing numbers of robust structures suitable for humid flue gas conditions, and the high adsorption capacity of these challenging humid flue gases will predict long-term stable adsorption performance for application in humid air. To bring coal fly ash-based carbon capture solutions to broader markets, further research is imperative in the fields of deciphering competitive adsorption mechanisms, designing efficient adsorbents, and developing low-cost and compact adsorption-based carbon capture systems.