Cyclodextrin-Grafted Double-Network Polysaccharide Hydrogels-Derived Porous Carbon Spheres for Enhanced Polycyclic Aromatic Hydrocarbons Adsorption

Efficient separation of polycyclic aromatic hydrocarbons (PAHs) from fluid catalytic cracking (FCC) diesel is crucial for fuel upgrading and resource recovery. Natural polysaccharides offer sustainable adsorbents. In this study, chitosan (CS) and hyaluronic acid (HA) were used to construct a double-network hydrogel framework via electrostatic self-assembly, aiming to overcome the poor mechanical stability of a single network. However, the interpenetrating network often suffers from densification, which compromises porosity and mass transfer. To mitigate this issue and introduce specific host–guest recognition sites, β-cyclodextrin (β-CD) was grafted onto the HA backbone, creating a functional biopolymer (HA-CD). Its rigid macrocyclic structure acted as a molecular spacer within the CS network, alleviating densification and forming stable hierarchical channels. The β-CD functionalized HA-CD/CS is formed by ionic cross-linking and could be shaped into spheres for easy handling. Furthermore, to enhance PAHs adsorption performance, the hydrogel was pyrolyzed to generate porous carbon spheres with a high specific surface area and abundant micropores. The HA-CD/CS-1000 demonstrated excellent adsorption capacities for PAHs (e.g., 102.01 mg/g for anthracene) and good selectivity. This work presents a green pathway from tunable biobased hydrogels to functional porous carbons, offering a promising material platform for the selective recovery of aromatic contaminants from complex hydrocarbon streams.