关键词: β-环糊精, 木粉, 接枝, 吸附, Pb²⁺, 动力学, 热力学

Abstract: β-cyclodextrin/wood flour (β-CD/WF) grafted copolymer was prepared by esterification- crosslinking technology, i.e., grafting β-CD onto poplar wood flour in the presence of citric acid. The properties of this grafted copolymer were characterized by FT-IR, TGA and the technique of phenolphthalein probe respectively. The adsorption property of this copolymer for Pb²⁺ in a batch adsorption system as a function of contact time, pH and initial Pb²⁺ concentration was investigated in this study. The results showed that β-CD was not only grafted onto the surface of wood flour but also demonstrated an encapsulation activity. The kinetic data were analyzed by the pseudo-first,second-order kinetics and intraparticle diffusion, and the equilibrium data were analyzed using Langmuir and Freundlich isotherm models. The results showed that adsorption equilibrium was reached within 30 min at 298 K under the proper pH between 4.0 and 8.0 , and the adsorption capacity increased with the rise of initial Pb²⁺ concentration. It was found that the adsorption kinetics followed the second-order model. This suggested that the adsorption of Pb²⁺ by copolymer was a chemisorption process, and the intraparticle diffusion was not the primary rate-determining step. Besides, Langmuir model fitted the equilibrium data better than the Freundlich isotherm. It reflected the adsorption of Pb²⁺ on copolymer was monolayer adsorption. The thermodynamic properties, ΔG^Θ, ΔH^Θ and ΔS^Θ showed that adsorption of Pb²⁺ onto β-CD/WF flour grafted copolymer was endothermic and spontaneous in the temperature range of 293-313 K.

Key words: β-cyclodextrin, wood flour, grafting, adsorption, Pb²⁺, kinetics, thermodynamics