Kinetics and Thermodynamics of Adsorption of Benzil-Bridged <i>β</i>-Cyclodextrin on Uranium(VI)

Abstract

Sulfated β-cyclodextrin (β-CD) was prepared by the reaction of β-CD with p-toluenesulfonyl chloride at low temperature in aqueous sodium hydroxide. The product was analyzed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance ( 1 H NMR). The novel benzil-bridged β-CD (BB β-CD) was acquired by the reaction of benzil with sulfated β-CD at a molar ratio of 1 : 2. UV spectrophotometry was used to study the synthetic mechanism of BB β-CD and benzil and their adsorption onto U(VI). Scanning electron microscopy (SEM) was used to analyze the surface properties of the materials. The adsorption of BB β-CD onto U(VI) was investigated as a function of pH, contact time, temperature, and interfering ions using the batch adsorption technique. It was found that the adsorption equilibrium of BB β-CD was reached faster than that of benzil. The optimum experimental conditions were pH = 4.5 and shaking for 60 min, achieving the maximum adsorption capacity of 12.16 mg•g -1 and a U(VI) removal ratio of 91.2% . Kinetic studies revealed that the adsorption reached equilibrium within 60 min for U(VI) and followed a pseudo-second-order rate equation. The isothermal data correlated with the Langmuir model better than with the Freundlich model. The thermodynamic data indicated the spontaneous and endothermic nature of the process.