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用延展X射线吸收精细结构光谱(EXAFS)研究了不同温度对Zn(Ⅱ)-锐钛矿型TiO2吸附产物微观构型和吸附可逆性的影响机制.宏观的吸附-解吸实验表明,不同温度下的吸附等温线可以用Langmuir模型进行较好的描述(R2≥0.990).随温度升高,吸附等温线显著升高,Zn(Ⅱ)在TiO2表面的饱和吸附量由5℃时的0.125mmol·g-1增至40℃时的0.446mmol·g-1;而体系的不可逆性明显减弱,解吸滞后角θ由32.85°减至8.64°.求得体系反应的热力学参数ΔH、ΔS分别为24.55kJ·mol-1和159.13J·mol-1·K-1.EXAFS结果表明,Zn(Ⅱ)主要是通过共用水合Zn(II)离子及TiO2表面上的O原子结合到TiO2表面上,其平均Zn-O原子间距为RZn-O=(0.199±0.001)nm.第二配位层(Zn-Ti层)的EXAFS图谱分析结果表明,存在两个典型的Zn-Ti原子间距,即R1=(0.325±0.001)nm(边-边结合的强吸附)和R2=(0.369±0.001)nm(角-角结合的弱吸附).随温度升高,强吸附比例(CN1)基本不变而弱吸附比例(CN2)增加,两者比值(CN1/CN2)逐渐减小.该比值的变化从微观角度解释了宏观实验中温度升高,不可逆性减弱的吸附现象.
The effect of different temperature on the microstructure and adsorption reversibility of Zn (Ⅱ) -Anatase-type TiO2 was studied by means of extended X-ray absorption fine structure spectroscopy (EXAFS) .The macroscopic adsorption-desorption experiments showed that under different temperatures (R2≥0.990) .With the increase of temperature, the adsorption isotherm increased significantly, and the saturated adsorption capacity of Zn (Ⅱ) on the surface of TiO2 increased from 0.125 mmol · L -1 at 5 ℃ g-1 to 0.446 mmol · g-1 at 40 ℃, while the irreversibility of the system was significantly weakened and the θ of the desorption delay was reduced from 32.85 ° to 8.64 °. The thermodynamic parameters ΔH and ΔS of the system reaction were 24.55 kJ · Mol-1 and 159.13J · mol-1 · K-1.EXAFS results show that Zn (Ⅱ) is mainly bonded to the TiO2 surface by sharing hydrated Zn (II) ions and O atoms on the surface of TiO2, The O atom spacing is -0.1199 ± 0.001 nm. The results of EXAFS analysis of the second coordination layer (Zn-Ti layer) show that there are two typical Zn-Ti atomic spacings, R1 = (0.325 ± 0.001) nm (strong side-edge binding) and R2 = (0.369 ± 0.001) nm (weak angle-angle binding). With increasing temperature, the strong adsorption ratio Adsorption ratio (CN2) increases, the ratio of both (CN1 / CN2) gradually decreases. The ratio changes from macro microscopic explained the experiment temperature, irreversible adsorption phenomena diminished.