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Abstract
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Herein, for the first time, we employed three minor concentrations of Carbon Nanotubes (CNT), 2.5, 5, and 10 wt.%, as an auxiliary additive to boost the textural and structural features and CO2 capture potential of sol–gel-derived CaZrO3-CaO adsorbents. The corresponding xerogels were developed with 15/1 and 30/1 Ca/Zr molar ratios to minimize the required amount of prohibitive Zr-based precursor. For both types of CaZrO3-CaO adsorbents, 5 wt.% of CNT was recognized as the most efficient amount. In addition to 15.84 and 33.1% reduction in CaO crystallite sizes, 50.57 and 90.55% increments in pore volume values were reported for CaO adsorbents developed with 15/1 and 30/1 Ca/Zr molar ratios, respectively. Over 15 cycles under harsh CO2 capture conditions, the total amount of captured CO2 for both abovementioned types of Zr-promoted adsorbents raised from 2.01 and 1.96 to 2.92 and 3.01 g CO2/g adsorbent, sequentially. Zr-promoted CaO nanoadsorbents merged with 5 wt.% CNT showed the ultimate CO2 capture capacity of 0.164 and 0.149 g CO2/g adsorbent for xerogel prepared with 15/1 and 30/1 M ratios of Ca/Zr, respectively. Even though the xerogel containing a Ca/Zr molar ratio of 15/1 showed the best sorption durability and ultimate capture capacity, CNT more significantly affects the CaO xerogel developed with a Ca/Zr molar ratio of 30/1. It can be deduced that the low content of multi-walled CNT notably contributes to developing highly efficient and fluffy-like Zr-promoted xerogels containing minor concentrations of Zr-based species.
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