Passive direct air capture using calcium oxide powder
Passive direct air capture with CaO powder relies on water vapor for CO2 removal. Higher humidity levels enhance CaO hydration but hinder carbonation. Manipulating humidity levels can optimize CO2 removal efficiency.
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Passive direct air capture using calcium oxide (CaO) powder is a promising technology for removing carbon dioxide (CO2) from the atmosphere to combat climate change. The presence of water vapor is crucial for the carbonation reactions involved in this process, affecting the pathways and rates of CO2 removal. Experiments showed that higher relative humidity (RH) levels led to faster hydration rates of CaO, resulting in the formation of Ca(OH)2 (portlandite). However, passivation hindered carbonation, with the most significant carbonation observed at 80% RH. By manipulating RH levels, researchers achieved over 85% CaCO3 formation, indicating the potential for efficient CO2 removal. Separating hydration and carbonation processes allowed for nearly complete carbonation, achieving a CO2 removal rate of 1 ton for every 1.95 tons of Ca(OH)2 per day. This study sheds light on the impact of water vapor on CaO carbonation and highlights the importance of understanding these mechanisms for optimizing direct air capture technologies.
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