Efficient and ultrafast adsorption of aromatic amino acids by hyper-crosslinked porous cyclodextrin polymers with high adsorption capacity

Abstract

The adsorption separation technology is of key significance in the purification of aromatic amino acids (AAAs) and the production of their derivatives. However, defects are always present in existing adsorbents for AAAs with slow adsorption rates, low adsorption capacity, and poor regeneration performance. Therefore, there is an urgent need to develop more efficient adsorbents for AAAs to improve separation and purification efficiency and productivity. In this study, partially benzylated cyclodextrin-based hyper-crosslinked porous polymers (PBCD-B-D) were prepared, among which the one with β-cyclodextrin as monomer (PBβ-CD-B-D) exhibited an extremely rapid adsorption process, a high adsorption capacity for AAAs, and a good selectivity toward AAAs over other amino acids. Specifically, the adsorption of AAAs reached equilibrium within one minute, while the equilibrium adsorption capacities of PBβ-CD-B-D for Trp and Phe were up to 524.58 mg·g⁻¹ (almost the highest till now) and 189.48 mg·g⁻¹, respectively. The pseudo-second-order kinetic model and the Freundlich model were better suited for describing the adsorption process. The comprehensive analysis of experimental results suggested that host–guest cooperation and π-π interactions may be the two dominant factors affecting the adsorption of AAAs on PBβ-CD-B-D. In addition, PBβ-CD-B-D exhibited good reusability, with the adsorption capacity remaining at 83.67 % after 4 adsorption–desorption cycles. Due to its low cost, good reusability, and excellent adsorption performance, PBβ-CD-B-D has great potential for application in the adsorptive removal and recovery of AAAs.