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Received March 18, 2024
Accepted May 16, 2024
- This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Integrated Melamine Molecules on Microspherical Boehmite Particles via Spray Drying for Highly Effi cient CO 2 /N 2 Adsorption Separation
Abstract
A newly developed spherical boehmite and melamine composite with a mesoporous structure was successfully fabricated
through a spray drying system utilizing a mixture of boehmite sol and melamine. EDX–SEM, FTIR, and TGA analyses
confi rmed the integration of melamine into the boehmite network within the resulting composite. With an increase in melamine
content, the composites exhibited a gradual reduction in porosity compared to their pristine boehmite counterpart.
However, the CO 2 uptake of the composites continued to demonstrate improvement. The boehmite sample modifi ed with 5
mol% of melamine (IMB#5) demonstrated the highest CO 2 adsorption capacity at 19.2 cm 3 g −1 . This value surpassed the
original boehmite sample by 46.1% under conditions of 25 °C and 1 bar. The enhanced adsorption can be attributed to the
development of adsorptive affi nity facilitated by N-derived functional groups (–NH 2 and –CN) within the melamine structure
and their interaction with CO 2 . As a result, the CO 2 /N 2 separation factor and CO 2 /N 2 adsorptive selectivity using the ideal
adsorbed solution theory (IAST) over the IMB#5 sample were 113.3 and 3182, respectively, approximately 3 times and 9.2
times higher than those for the boehmite sample. Density functional theory (DFT) calculations were conducted to investigate
the interaction of melamine on the boehmite surface, as well as the selective adsorption of CO 2 and N 2 gaseous molecules on
the boehmite/melamine composite. It is shown that the melamine mainly interacts with the boehmite via a strong binding of
the N atom of the triazine ring with the Al atom of the boehmite. The adsorption of CO 2 has lower binding enthalpies and
free energies than that of N 2 . These fi ndings indicate that utilizing continuous spray drying holds promise as an eff ective
pathway for scaling up the production of mesoporous boehmite/melamine composite spheres as CO 2 selective adsorbents.