Fabrication of photo-responsive chitosan imprinted aerogels for selective adsorption and green desorption of dysprosium ions

The development of smart responsive materials is crucial for not only achieving high-performance adsorption of rare earth elements but also enabling green regeneration. Herein, we report the fabrication of ultraviolet (UV)-light responsive imprinted chitosan-based aerogel (UV-IA) and near-infrared (NIR)-light responsive imprinted chitosan-based aerogel (NIR-IA) for the selective adsorption and eco-friendly desorption of Dy(III). Both light-responsive imprinted chitosan-based aerogels were prepared by low-temperature thermally induced phase separation (LT-TIPs), and NIR-IA was prepared by adding the photo-thermal conversion material croconaine. The chitosan aerogels with nanofiber network pore structure were prepared by LT-TIPs. The adsorption capacities of 10   mg of UV-IA and NIR-IA were 76.32   mg   g -1 and 76.11   mg   g -1 under the condition of pH 5.0 and room temperature, respectively. The selective adsorption effect of UV-IA and NIR-IA on dysprosium ions was obviously better than other competitive ions, and their adsorption separation constants can reach 2408.45   mL   g -1 and 2623.29   mL   g -1 , respectively. The results showed that cinnamic acid in UV-IA changed to cis structure under UV irradiation, while croconaine in NIR-IA decomposed the chitosan/cinnamic acid conjugate by applying heat to it under NIR irradiation. These changes caused the imprint sizes of UV-IA and NIR-IA to be changed, realizing the green desorption of Dy(III). The best desorption rate of 88.64% was achieved by UV-IA. These materials provide a promising approach for the green and economical separation and recovery of Dy(III) from secondary resources.