mSiO2-IDA对Cu2+、Cd2+金属离子的吸附

在介孔二氧化硅（mSiO₂）的表面接枝了亚氨基二乙酸官能团（IDA）合成了mSiO₂-IDA吸附剂，研究了mSiO₂-IDA对Cu²⁺、Cd²⁺两种金属离子的吸附效果。通过元素分析仪（EA）、傅里叶红外型光谱仪（FT-IR）等表征手段表明IDA成功地接枝到mSiO₂的表面，考察了溶液的pH、初始浓度和吸附时间对吸附Cu²⁺、Cd²⁺的影响。结果显示，当pH=5，t=30 min时，2 g/L mSiO₂-IDA对溶液中的Cu²⁺、Cd²⁺去除率分别达到97.9%和92.1%。通过吸附动力学数据可知，拟二级动力学方程能更好地描述mSiO₂-IDA对Cu²⁺、Cd²⁺的吸附过程，它属于Langmuir等温吸附模型；多功能光电子能谱仪（XPS）研究显示mSiO₂-IDA对Cu²⁺、Cd²⁺的吸附机制并不相同。

Adsorption of Cu2+ and Cd2+ onto mSiO2-IDA

Because of the non-degradability of heavy metal ions and their serious injury to the human body, removal of heavy metal ions in industrial waste water has become very urgent. The adsorption method is widely used due to simple operation, low cost, and less secondary pollution. Mesoporous SiO₂ with a high specific surface, good thermal stability and mechanical property becomes a good metal adsorbent. In this study, mesoporous SiO₂ functionalized by iminodiacetic acid (IDA) (mSiO₂-IDA) was prepared to explore the adsorption of Cu²⁺ and Cd²⁺. The prepared mSiO₂-IDA was analyzed and characterized by elemental analysis (EA) and FT-IR spectroscopy, which confirmed that IDA was successfully grafted on the surface of mSiO₂. The effect of solution pH, initial metal ion concentration and time on the adsorption of Cu²⁺ and Cd²⁺ onto mSiO₂-IDA was studied. The capacity of adsorption changed with the increase of pH, the maximum adsorption appeared at pH=5. Then the kinetics of adsorption at pH=5 was studied. The adsorption rates and capacity reached the maximum within 30 min. Besides, the adsorption capacity of mSiO₂-IDA at different initial concentrations was studied. Adsorption capacity increased with the increase of initial concentrations and the highest adsorption capacities were 49.0 mg/g and 43.5 mg/g for Cu²⁺ and Cd²⁺ respectively. It was concluded that the removal efficiency of Cu²⁺ and Cd²⁺ achieved 97.9% and 92.1% within 30 min respectively at pH=5 by 2 g/L mSiO₂-IDA. Meanwhile, in order to determine the adsorption rate constant and explore adsorption mechanism of mSiO₂-IDA to Cu²⁺ and Cd²⁺, their data of adsorption kinetics were fitted. The adsorption behavior was better described by pseudo-second-order equation, and the adsorption isotherm followed Langmuir one. As revealed by X-ray photoelectron spectroscopy (XPS), the adsorption mechanisms of Cu²⁺ and Cd²⁺ onto mSiO₂-IDA are different. mSiO₂-IDA showed a good adsorption performance to Cu²⁺ and Cd²⁺.