Preparation of β-cyclodextrin-reduced graphene oxide aerogel and its application for adsorption of herbicides

Herbicides are the primary pesticides that can easily pollute water bodies, attracting significant attention from researchers regarding the effective removal of herbicide residues from the water environment. In this study, a beta-cyclodextrin-reduced graphene oxide (beta-CD-BTCA-rGO) aerogel was prepared following the self-assembly hydrothermal method using 1,2,3,4-butane tetracarboxylic acid (BTCA) as crosslinkers. The self-assembly process involved the cross-linking of "soft" beta-cyclodextrin (beta-CD) with "hard" graphene oxide (GO) nanosheets, forming a stable beta-CD-BTCA-rGO aerogel. The prepared beta-CD-BTCA-rGO aerogel demonstrated excellent adsorption performance. The adsorption capacities were 62.3 and 46.8 mg/g for sulfentrazone and quinclorac, respectively, surpassing the traditional reduced graphene oxide (rGO) aerogel and citric acid cross-linked (beta-CD-CA-rGO) aerogel. Correspondingly, its adsorption capacity for quinclorac was 1.8 times and 12 times that of rGO aerogel and beta-CD-CA-rGO aerogel, respectively. Quantum chemical calculations at the density functional theory (DFT) level, utilizing the Fukui function to predict chemical reaction sites, indicated that BTCA, as crosslinkers, formed stable chemical bonds (ester bonds) with GO through hydroxyl and carboxyl surface functional groups, leading to the formation of stable porous aerogels. Furthermore, the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap was quantitatively measured for various adsorption mechanisms, revealing that electrostatic adsorption was the main force of the adsorption on the aerogels. The beta-CD-BTCA-rGO aerogels prepared in this study demonstrated economic feasibility as adsorbents and exhibited good reproducibility. Consequently, beta-CD-BTCA-rGO aerogels hold promising application prospects in the remediation of pesticide pollution in water systems.