Developing cost-effective and high-performance solid amine adsorbents has considered as an important way to alleviate the greenhouse effect. How to precisely regulate its pore structure and surface interface characteristics, and how to cooperate to optimize the dynamic mass transfer and adsorption–desorption behavior of gas in the adsorbent are still challenging work. Herein, we demonstrated a facile and efficient approach to construct polyethyleneimine (PEI) impregnated halloysite nanotubes (HNTs) as an emerging nanocomposite for CO capture. Based on the natural electrostatic differences of inner and outer walls for HNTs, the hollow tubular structures of adsorbents were constructed by selective surface modification and layer-by-layer electrostatic self-assembly technology to improve the CO uptake capacity and cyclic stability, in which poly(sodium--styrene sulfonate) (PSS) and PEI were used as polyanionic and polycationic layer, respectively, to coat the inner walls of HNTs. The loading capacity of PSS-PEI composite ionic layers in HNTs and the influence of PSS polyanionic layer on PEI dispersion were specifically discussed according to the CO uptake capacity, adsorption heat, thermodynamics and kinetics of the adsorbents. The optimal PEI20-0.5PHNTs adsorbent exhibited a higher CO uptake of 0.87 mmol/g at 80 °C in the flow of 40 vol% N/60 vol% CO than that of PEI20-HNTs, owing to the high amine efficiency due to the uniform dispersion of PEI in the electrostatic composite ionic layers. Furthermore, PEI20-0.5PHNTs reached 75 % of the maximum adsorption capacity at the 5th min of the adsorption process and released the most heat during adsorption at − 18.28 kJ/mol due to the presence of electrostatic composite ionic layers. PEI20-0.5PHNTs showed excellent cyclic stability with a slight loss of 7.4 %. The electrostatic self-assembled adsorbent obtained by layer-by-layer loading of PSS and PEI based on the unique surface charge characteristics of HNTs is an inspiration for the synthesis of cost-effective solid amine adsorbents for practical CO capture and separation.

中文翻译：

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通过层层静电自组装方法的胺浸渍天然无机纳米管可有效吸附二氧化碳

开发高性价比、高性能的固体胺吸附剂被认为是缓解温室效应的重要途径。如何精确调控其孔隙结构和表面界面特性，以及如何配合优化气体在吸附剂中的动态传质和吸附-解吸行为仍然是具有挑战性的工作。在此，我们展示了一种简便有效的方法来构建聚乙烯亚胺（PEI）浸渍埃洛石纳米管（HNT）作为一种用于二氧化碳捕获的新兴纳米复合材料。基于HNT内外壁的天然静电差异，通过选择性表面改性和层层静电自组装技术构建吸附剂中空管状结构，以提高CO吸附能力和循环稳定性。 (钠--苯乙烯磺酸)(PSS)和PEI分别作为聚阴离子和聚阳离子层来涂覆HNT的内壁。根据吸附剂的CO吸收能力、吸附热、热力学和动力学，具体讨论了PSS-PEI复合离子层在HNT中的负载能力以及PSS聚阴离子层对PEI分散性的影响。最佳的 PEI20-0.5PHNTs 吸附剂在 80 °C、40 vol% N/60 vol% CO 流中表现出比 PEI20-HNTs 更高的 CO 吸收量，为 0.87 mmol/g，这是由于胺效率高，这是由于PEI在静电复合离子层中的均匀分散。此外，PEI20-0.5PHNTs 在吸附过程第 5 分钟就达到了最大吸附容量的 75%，并且由于静电复合离子层的存在，在吸附过程中释放了最多的热量，为 − 18.28 kJ/mol。 PEI20-0.5PHNT表现出优异的循环稳定性，轻微损失了7.4%。基于HNT独特的表面电荷特性，通过逐层负载PSS和PEI获得的静电自组装吸附剂，为合成用于实际CO捕获和分离的经济有效的固体胺吸附剂提供了灵感。