磁性多壁碳纳米管吸附水中重金属离子的动力学与热力学

采用湿式化学法合成了磁性多壁碳纳米管(MWCNTs),用透射电镜、X-射线衍射、傅里叶变换红外光谱、比表面积分析仪对磁性MWCNTs的表面特性进行了表征.考察了溶液pH值、吸附时间等因素对水中镉(II)、铜(II)和锌(II)吸附过程的影响.结果表明:金属离子的吸附过程强烈依赖于pH值,金属离子的去除率随着溶液pH值的增大而增大,当溶液pH值达到一定值时,去除率达到最大,然后保持不变;吸附动力学分析与等温线拟合表明,准二级模型准确地反映了吸附过程的动力学,Freundlich等温线更好地说明了升高温度有利于吸附的事实.对热力学参数(ΔH0,ΔS0和ΔG0)的计算结果揭示了吸附过程具有自发且吸热的性质.

Kinetics and Thermodynamics of Adsorption of Heavy Metal Ions on Magnetic Multi-walled Carbon Nanotubes in Aqueous Solutions

The magnetic multi-walled carbon nanotubes （MWCNTs） were synthesized by wet chemical treatments; and the surface properties of magnetic MWCNTs were characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and specific surface area analyzer. The effects of pH values and adsorption time of the im- pact on the adsorption of Cd （ Ⅱ ）, Cu （ Ⅱ ） and Zn （Ⅱ） ions in aqueous solutions were discussed. The results showed that the adsorption was strongly dependent on pH values, that the removal rate of metal ions increased with solution pH values, and that the rate was at the maximum and remained unchanged when the solution pH value reached a certain degree. Adsorption kinetics analysis and isotherm fitting demonstrated that the pseudo second order model could accurately represent the kinetics of adsorption process, and that Freundlich isotherm better explained that the high temperature was beneficial to the adsorp- tion experiments. The calculating results of the thermodynamic parameters （ΔH0, ΔS0,ΔG0） revealed that the adsorption process was spontaneous and endothermic.