黄原胶-丙烯酰胺接枝共聚物吸附Cu(Ⅱ)的热力学、动力学性质

摘要

Graft copolymer of xanthan gum and acrylamide (XG-g-AM) was used to adsorb Cu (Ⅱ) from aqueous solution.Thermodynamics and kinetic characteristics of the adsorption process were investigated based on the adsorption experiment.The molecular structures of XG-g-AM before and after adsorption were characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD).The results show that the adsorption pattern of XG-g-AM for Cu (Ⅱ) fits with both the Langmiur and Freundlich adsorption isotherm equation within the temperature range of 298～ 318K.Thermodynamic parameters,the change of free energy (ΔG),enthalpy (ΔH) and entropy (ΔS),indicate that the adsorption is a spontaneous,endothermic and entropy increase process.Moreover,temperature increase can benefit the adsorption.Kenetic experiments show that the adsorption process corresponds with pseudo-second order kinetic model.XG-g-AM adsorbs Cu (Ⅱ) by means of physical adsorption and coordination adsorption.The crystal structure of XG-g-AM was destroyed after adsorbing Cu (Ⅱ) and the crystallinity of XG-g-AM decreased.Cu (Ⅱ) congregate on XG-g-AM in the form of non crystalline state.%利用黄原胶-丙烯酰胺接枝共聚物(XG-g-AM)吸附溶液中的Cu(Ⅱ),通过静态吸附实验研究了吸附过程中的热力学和动力学性质,使用红外光谱仪和X射线衍射仪对XG-g-AM吸附Cu(Ⅱ)前后的分子结构进行了表征.研究结果表明:在298～318K温度范围内,吸附行为可同时用Freundlich等温式和Langmuir等温式进行描述,吸附为自发的、吸热的熵增加过程,温度升高有利于吸附.吸附过程符合伪二级动力学模型.XG-g-AM通过物理和配位吸附方式吸附Cu(Ⅱ),吸附Cu(Ⅱ)后,XG-g-AM的结晶结构被破坏,结晶度下降.Cu(Ⅱ)以非结晶态形式在XG-g-AM上聚集存在.