纳米TiO_2对钼(Ⅵ)的吸附性能

研究纳米TiO_2对Mo(VI)的吸附过程,考察溶液的pH值、时间、温度等因素对吸附的影响.结果表明:在pH 1～8范围内,纳米TiO_2对Mo(VI)的吸附率均超过99%,吸附于纳米TiO_2上的Mo(VI)可用2.0 mL的0.1 mol/L NaOH溶液定量洗脱;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22.7 kJ/mol,粒子内部扩散过程是其吸附控制步骤,但液相边界层向粒子表面的扩散过程不能忽略;吸附行为服从Langmuir和D-R等温模型.在室温下,纳米TiO_2对Mo(VI)的饱和吸附容量为12.74 mg/g,平均吸附能为17.36 kJ/mol;吸附反应焓变和熵变均为正值,自由能变为负值,说明该吸附过程为自发的吸热过程.

Adsorption properties of nano-TiO_2 for Mo(VI)

Titanium dioxide nanoparticles were employed for the sorption of Mo(VI) ions from aqueous solution. The process was studied in detail by varying the pH value, sorption time and temperature. The adsorption rate of Mo(VI) by the sorbent is over 99% at pH 1-8. Adsorbed Mo(VI) were desorbed by 2.0 mL of 0.1 mol/L NaOH. The kinetic experimental data properly correlate with the second-order kinetic model. The apparent activation energy is 22.7 kJ/mol. The overall rate process is mainly controlled by the intraparticle diffusion, while the boundary layer resistance cannot be ignored. The sorption data could be well interpreted by the Langmuir and D-R type sorption isotherms. At room temperature, the static saturated adsorption capacity is 12.74 mg/g, and the average sorption energy is 17.36 kJ/mol. The thermodynamic parameters: ΔH~Θ＞0, ΔS~Θ＞0 and ΔG~Θ＜0, which indicates a spontaneous and decalescence adsorption process.