Recent advances in carbon dioxide capture using calcium oxide promoted with molten salts: A comprehensive review

The buildup of carbon dioxide (CO₂) concentration in the atmosphere is one of the serious challenges the world is currently facing. The increased frequency of natural disasters has been linked to global warming and climate change, driven by the continuous increase in the atmospheric level of CO₂. Accordingly, mitigating CO₂ emissions through the development of effective and feasible CO₂ capture technologies is inevitable. Calcium oxide (CaO)-based sorbents have emerged as a practical option for CO₂ capture due to their wide availability, low cost and high CO₂ uptake capacity. Optimum design of CaO supports and the promotion of CaO with various alkali salts could potentially result in a significant enhancement of CO₂ capture, bringing these attractive materials a step closer to practical applications. The key objective of this article is to comprehensively review recent advances in CO₂ capture using CaO-based sorbents supported on various materials and promoted with different molten salts. The scope of this review article also includes the discussion of promoter families and loadings, sorbent synthesis strategies (e.g., co-precipitation, sol–gel, wet mixing/impregnation, combustion) and the role of supports that form stabilizing phases. Additionally, the effects of operating conditions on shaping the performance of CaO-based adsorbents in capturing CO₂ are assessed. Furthermore, the mechanistic models used to interpret CaL kinetics are surveyed and discussed. Moreover, long-cycle stability across different synthesis recipes and conditions of CaO-based adsorbents are discussed, and practical trade-offs and research gaps are highlighted. By mitigating CO₂ emissions via robust, regenerable sorbents, molten salt-promoted CaO remains a promising route for scalable and cost-effective post-combustion capture.