Modified β-Cyclodextrin hydrogel for selective adsorption and desorption for cationic dyes

The treatment of dye wastewater is one of most important environmental problems in the world. In this work, the beta-cyclodextrin (beta-CD) was simply modified and copolymerized with acrylamide and acrylic acid to prepare a novel composite hydrogel as an efficient adsorbent for selective adsorption of cationic dyes. During the adsorption performance tests, the material exhibited excellent removal efficiency of towards of methylene blue (MB), reaching 94.9% in 30 min, and showed excellent selective adsorption in methylene blue/Congo red (CR), methyl blue/methyl orange (MO), methyl green (MG)/ Congo red, methyl green/methyl orange mixture solutions. Studies on the adsorption kinetics suggested that the adsorption behavior follows Pseudo-second-order kinetics model, while the adsorption isotherm of the hydrogel was more consistent with the Freundlich isotherm. In addition, desorption performance of these hydrogels was also investigated in detail, with the screening of the desorption conditions. Under the economical and eco-friendly conditions, it was found that the efficiency of desorption can reach 88% in 75% ethanol solution of oxalic acid, and the adsorption capacity of hydrogel in the next cycle of adsorption still reached 93.4%. Overall, the hydrogel is a potential adsorbent for the efficient cleaning of wastewater and recycling of dyes.