改性加拿大一枝黄花去除水中Cr(Ⅵ)的特性分析
Adsorption of Cr(Ⅵ) from aqueous solution by modified Solidago canadensis
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摘要: 以生物入侵植物加拿大一枝黄花为原料,利用环氧氯丙烷、氢氧化钠和三乙胺对其进行化学改性,制备出含季铵基的吸附剂.采用元素分析、扫描电镜、X射线衍射、红外光谱、氮气吸附和X射线光电子能谱等手段对改性前后加拿大一枝黄花物理化学性质进行表征,并通过批实验的方法探讨了改性前后加拿大一枝黄花对Cr(Ⅵ)的吸附行为及热力学性质.结果表明,加拿大一枝黄花改性后纤维素内部产生了爆裂式膨胀,含氮量增加,引入了季铵基,吸附Cr(Ⅵ)离子能力显著提高.吸附实验结果表明,改性加拿大一枝黄花吸附去除Cr(Ⅵ)的平衡时间约为3 h,pH值为1—7范围内吸附效果较好.吸附过程符合准二级动力学模型,并均能较好地符合Langmuir和Freundlich等温吸附模型(R2> 0.95),298 K时最大吸附量为29.62 mg·g-1.应用van't Hoff 方程对吸附热力学参数进行了计算,结果表明Cr(Ⅵ)在改性加拿大一枝黄花上的吸附为熵加的自发物理吸热过程.Abstract: Solidago canadensis was modified with epichlorohydrin, sodium hydroxide and triethylamine for the removal of hexavalent chromium from aqueous solution. The modified Solidago Canadensis (MSC) was characterized by element analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), nitrogen adsorption and X-ray photoelectron spectroscopy (XPS). The adsorption of hexavalent chromium from aqueous solutions with MSC which contained amine groups was investigated under several conditions in batch methods. The results showed that the hollow shape was formed along the longitudinal cellulose strongly, and nitrogen content in MSC was increased. Batch adsorption experimental results indicated that adsorption behavior of MSC was significantly depending on pH, contact time, and initial concentration of Cr(Ⅵ). The adsorption equilibrium time was about 3 hours, and the proper pH range was 1—7. Kinetic data were best fitted with the pseudo-second-order kinetic model. The batch equilibrium data was fitted well to both Langmuir and Freundlich adsorption model (R2> 0.95). Maximum adsorption capacity of MSC for Cr(Ⅵ) was 29.62 mg·g-1 at 298 K. Thermodynamic parameters such as standard Gibbs free energy (ΔG0), standard enthalpy (ΔH0), and standard entropy (ΔS0) were evaluated by applying the van't Hoff equation. The obtained thermodynamic parameters showed that the adsorption of Cr(Ⅵ) onto MSC was a spontaneous and endothermic process.
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Key words:
- modified Solidago Canadensis /
- Cr(Ⅵ) /
- adsorption /
- isotherms /
- kinetics /
- thermodynamics.
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