改性MCM-41的制备及其吸附Cr_2O_7^(2-)的热力学研究

Synthesis of thiol-functionalized mesoporous silica and the thermodynamics of the adsorption of Cr_2O_7^(2-)

以微硅粉为硅源,CTAB和PEG-6000为模板剂,采用水热法制备得到MCM-41介孔分子筛。以该MCM-41为载体,采用后接枝法将巯丙基三甲氧基硅烷引入到MCM-41的表面和孔道内,合成了巯基功能化的MCM-41介孔分子筛(SH-MCM-41),并采用XRD、N2吸附-脱附曲线和FT-IR对样品进行了表征。以巯基功能化的样品为吸附剂,对含Cr2O2-7的溶液进行了静态吸附实验,研究了pH值和初始浓度对吸附剂吸附性能的影响,探讨了吸附过程的热力学。结果表明,吸附剂吸附量随初始浓度和温度升高而增加,当pH值为1时吸附容量最大,达25.5mg/g。不同温度下Langmuir方程均呈现很好的拟合度,热力学平衡方程计算得ΔG<0,ΔH=14.2kJ/mol,ΔS>0,表明该吸附过程是自发的、吸热、熵增加的过程。

Using the silica fume as silica source,CTAB and PEG-6000 as template agent,the MCM-41 meso-porous silica materials were successfully synthesized.3-Mercaptopropyl trimethoxysilane was introduced into the network of MCM-41 through post-grafting and thiol-functionalized MCM-41 mesoporous silica (SH-MCM-41)was obtained.The SH-MCM-41 was characterized by XRD,N2 adsorption-desorption isotherm,and FT-IR.Cr2 O2-7 adsorption characteristics in water solution have been studied in static experiments with the SH-MCM-41 as adsorbent.The influence of solution pH value and initial metal ion concentration was investigated. And the thermodynamics of Cr2 O2-7 adsorption onto SH-MCM-41 was also studied.It was showed that adsorp-tion capacity of Cr2 O2-7 increased with increasing initial metal ion concentration and temperature.And its high-est value was 25.5 mg/g at pH 1.Experimental data fitted well to the Langmuir model at all temperatures studied.The thermodynamic equilibrium functions were also determined.ΔG<0,ΔH=14.2 kJ/mol,ΔS>0, so the adsorption was spontaneous,endothermic and entropy increasing.