负载型纳米钛酸锶钡对水中Cd^2＋吸附行为研究

Adsorption Behavior of Immobilized Nanometer Barium-Strontium Titanate for Cadmium Ion in Water

采用络合溶胶-凝胶法制备了钛酸锶钡溶胶，将其浸渍在硅胶G上，经高温煅烧后，制得固载于硅胶G上的纳米钛酸锶钡，以X射线衍射（XRD）、扫描电镜（SEM）和傅里叶变换红外光谱（FTIR）进行了表征。以火焰原子吸收为检测手段，系统地研究了负载型纳米钛酸锶钡对水中Cd^2＋的吸附行为。结果表明，纳米钛酸锶钡能够牢固地负载于硅胶G表面。当介质的pH值为4～7时，该吸附剂对水中的Cd^2＋具有很强的吸附能力，其吸附行为符合Freundlich吸附等温模型和HO准二级动力学方程式，并分别计算了吸附过程的焓变（△H），自由能变（△G）和熵变（△S）等热力学参数，表明该吸附过程是自发的吸热物理过程。被吸附的Cd^2＋可用1mol·L^-1的硝酸完全洗脱回收。将其应用于水中痕量Cd^2＋的吸附，建立了负载型纳米钛酸锶钡吸附富集，火焰原子吸收法测定水中痕量Cd^2＋的新方法。用于自来水和地表水中镉的测定，结果满意。

Nanometer barium-strontium titanate immobilized on silica gel G was successfully prepared by the citrate acid sol-gel method and characterized using X-ray diffraction （XRD）, scanning electron microscope （SEM） and Fourier transform infrared spectrophotometer （FTIR）. By means of the determination of flame atomic absorption spectrometry（FAAS）, the adsorption behavior of immobilized nanometer-barium strontium titanate for cadmium ion was investigated. The results showed that the nanometer barium-strontium titanate was immobilized on the silica gel G firmly, gaining a new sort of adsorbent. And the cadmium ion studied could be quantitatively retained in the pH value range of 4-7. The adsorption behavior followed a Freundlich adsorption isotherm and a pseudo-second-order kinetic model. The thermodynamic constants of the adsorption process, such as enthalpy changes（△H）, Gibbs free energy changes（△G） and entropy changes（△S）, were evaluated. These showed that the adsorption of cadmium ion by immobilized nanometer barium-strontium titanate was endothermic and spontaneous physical process. The cadmium ion adsorbed could be completely eluted using 1 mol · L^-1 HNOa. A new method for the determination of trace cadmium ion in water based on this immobilized nanometer barium-strontium titanate preconcentration and FAAS determination was proposed. The method has been applied to the determination of trace cadmium ion in tap water and river water with satisfactory results.