纳米TiO_2对镉(Ⅱ)的吸附性能

Adsorption properties of nano-TiO_2 for Cd(Ⅱ)

通过吸附实验研究纳米TiO2对Cd(Ⅱ)的吸附行为,考察溶液的pH值、吸附时间和温度等因素对吸附的影响。结果表明:在pH为4～7范围内,纳米TiO2对Cd(Ⅱ)的吸附率均超过97%,吸附于纳米TiO2上的Cd(Ⅱ)可用7.0 mL 0.1 mol/L HCl于70℃恒温水浴中定量洗脱;该吸附过程符合准二级反应动力学模型,其反应的表观活化能为3.16 kJ/mol,粒子内部扩散过程是其吸附过程的速率控制步骤,但液相边界层向粒子表面的扩散过程亦不能忽略;等温吸附数据与Langmuir和D-R等温模型拟合较好。在室温下,纳米TiO2对Cd(Ⅱ)的饱和吸附容量为6.34 mg/g,平均吸附能为11.54 kJ/mol;吸附反应的焓变和熵变均为正值,自由能为负值,说明该吸附过程为自发的吸热过程。

The titanium dioxide nanoparticles were employed for the sorption of Cd（Ⅱ） ions from aqueous solution.The process was studied by varying the pH,sorption time and temperature.The adsorption rate of Cd（Ⅱ） by the sorbent is over 97% at pH of 4-7.The adsorbed Cd（Ⅱ） are desorbed by 7.0 mL 0.1 mol/L HCl in constant temperature water bath at 70 ℃.The kinetic experimental data properly correlate with the second-order kinetic model.The apparent activation energy is 3.16 kJ/mol.The overall rate process is mainly controlled by the intraparticle diffusion,while the boundary layer resistance cannot be ignored.The sorption data can be well interpreted by the Langmuir and D-R type sorption isotherms.At room temperature,the static saturated adsorption capacity is 6.34 mg/g,and the average sorption energy is 11.54 kJ/mol.The thermodynamic parameters： ΔHΘ0,ΔSΘ0 and ΔGΘ0,which indicates a spontaneous and decalescence adsorption process.