β-环糊精聚合物微球对Zn^(2+)的吸附行为及机理

Adsorption Behavior and Mechanism of Zinc(Ⅱ) on β-Cyclodextrin Polymer Microspheres

以β-环糊精为原料,环氧氯丙烷为交联剂,采用反相乳液聚合得到一种交联β-环糊精聚合物(β-CDP)微球,研究其对Zn2+的静态吸附行为,测定吸附等温线,分析吸附热力学性质和动力学特征,并用红外光谱仪、X射线衍射仪和综合热重仪对β-CDP微球吸附Zn2+前后对照分析,探讨吸附机理。结果表明:在实验条件范围内,β-CDP微球对Zn2+吸附等温线同时符合Langmuir等温方程和Freundlich等温方程;在不同温度下,β-CDP微球吸附Zn2+的吸附焓变(ΔH)、熵变(ΔS)、吉布斯自由能(ΔG)均为负值,吸附是自发的放热过程;β-CDP微球主要通过物理吸附和配位吸附等方式吸附Zn2+,这些吸附作用增强了交联链的热稳定性、破坏了β-CDP微球的结晶结构。

The static adsorption behavior of Zn2＋ on β-cyclodextrin polymer（β-CDP） microspheres prepared by crosslinking of β-cyclodextrin with epichlorohydrin and subsequent reversed-phase emulsion polymerization was investigated,and the isothermal adsorption curves and the adsorption thermodynamics and kinetics characteristics were measured at different temperatures.Meanwhile,structural changes in β-CDP microspheres before and after Zn2＋ adsorption were examined through FT-IR spectroscopic and X-ray diffraction（XRD） observations and thermogravimetric analysis（TGA）,and the adsorption mechanism was also discussed.The results showed that the adsorption of Zn2＋ on β-CDP microspheres complied with both Langmuir and Freundlich isotherm adsorption equations.The enthalpy change（ΔH）,entropy change（ΔS） and free energy change（ΔG） for Zn2＋ adsorbed by β-CDP microspheres at different temperatures were all negative,meaning that the adsorption of Zn2＋ on β-CDP microspheres is a spontaneous and exothermic process.β-CDP microspheres adsorbed Zn2＋ mainly through physical adsorption,coordination adsorption,and so on,which could enhance the thermostability of crosslinked chains and damage the crystal structure of β-CDP microspheres.