巯基硅烷改性多壁碳纳米管的合成及其对Cd2+的吸附性能研究

利用3-巯丙基三甲氧基硅烷(MPTMS)作硅烷偶联剂对多壁碳纳米管(MWCNTs)进行改性,制备巯基硅烷改性多壁碳纳米管(SHMWCNTs),并进行了SH-MWCNTs对Cd~(2+)的批量吸附实验.同时,利用扫描电镜(SEM)、X射线光子能量仪(EDS)、红外光谱(FT-IR)对SHMWCNTs进行表征,探究了溶液初始pH、吸附剂投加量、吸附时间、溶液初始Cd~(2+)浓度等因素对吸附效果的影响,分析了吸附动力学特征及吸附等温线特征,初步探讨了吸附机理.SEM、EDS与FT-IR图谱显示,MPTMS已成功接枝到MWCNTs表面,表明SH-MWCNTs制备成功.吸附时间为90 min,pH为4时的吸附效果最佳,吸附量随SH-MWCNTs投加量、Cd~(2+)浓度的增加而增大.吸附动力学和吸附等温线研究表明,SHMWCNTs对Cd~(2+)的吸附动力学符合准二级线性方程,吸附等温线符合Freundlich、Langmuir 2种模型,吸附以单分子层吸附为主,也存在层间扩散的多层吸附.

Synthesisof sulphydryl silane-modified multiwall carbon nanotubes and its cadmium adsorption capacity

To enhance heavy metal adsorption capacity of multi-walled carbon nanotubes (MWCNTs), sulphydryl multi-walled carbon nanotubes (SH-MWCNTs) were synthesized using 3-mercaptopropyl trimethoxysilane as silane coupling agent to modify MWCNTs. Scanning Electron Microscope, Energy Dispersive X-Ray Spectrometer and Fourier Transform Infrared Spectrometer were employed to characterize the physical and chemical properties of SH-MWCNTs. It was found that sulphydryl groups were successfully grafted onto the surface of MWCNTs. A batch equilibration method was used to determine the effect of modification on Cd²⁺ adsorption capacity of the MWCNTs, under various initial solution pH, adsorbent dosage, adsorption time, and initial Cd²⁺ concentrations. The characteristics of adsorption isotherms and adsorption kinetics were analyzed to reveal associated mechanisms. The results show that adsorption of Cd²⁺ increased with the application rate of SH-MWCNTs and initial Cd²⁺ concentration in solution. The greatest adsorption of Cd²⁺ on SH-MWCNTs occurred at the initial pH 4 after 90 min. The adsorption kinetics corresponded to the pseudo-second order linear equations. The adsorption isotherms demonstrated that the adsorption of Cd²⁺ to the SH-MWCNTs was well described by both Freundlich and Langmuir models. Monolayer adsorption was the main adsorption process, although there were also multilayer adsorptions.