粉煤灰基沸石对Pb^(2+)的吸附动力学与热力学

Kinetic and Thermodynamic Study on Pb^(2+) Adsorption onto Synthesized Zeolite Based on Fly Ash

以电厂粉煤灰为原料,在传统碱熔-水热法基础上,引入脱硅工艺,制备得到SOD型沸石,运用XRD和SEM技术对合成沸石进行了表征,通过静态平衡吸附实验研究了合成沸石对Pb^(2+)的吸附动力学和热力学特性。表征结果显示,样品的XRD图谱与SOD型沸石标准卡片吻合,SEM图中可见典型的SOD型沸石形貌。结果表明,在初始Pb^(2+)质量浓度为100 mg/L、吸附温度为25℃、溶液p H值为10、投加量为2 g/L的条件下,合成沸石对Pb^(2+)的去除率即能超过99%;以Langmuir等温吸附模型拟合的最大吸附量为157.2 mg/g;吸附过程可用准二阶和Elovich动力学方程来描述;合成沸石对Pb^(2+)的吸附是自发的吸热过程;该过程以物理吸附为主,并伴随化学吸附。

On the basis of conventional alkali fusion hydrothermal synthesis method, the process of removing silicon was introduced. Zeolite SOD was prepared by this method using fly ash from power plant and characterized by X ray diffraction and scanning electron microscope. And then, the adsorption kinetics and thermodynamics characteristics of Pb^2＋ on synthetic zeolite were investigated. In addition, the change in synthetic zeolite before and after adsorption was analysed by infrared and X ray diffraction. The characterization results show that the XRD spectra of the samples were in agreement with the standard card of zeolite SOD and the typical morphology of zeolite SOD can be seen in the SEM diagram. The experimental results show that the equilibrium adsorption rate of Pb^2＋ on synthetic zeolite exceed 99% in the condition of the initial Pb^2＋ mass concentration 100 mg/L, adsorption temperature 25 ℃, solution p H 10, adsorbent dosage is 2 g/L. The theoretical maximum adsorption capacity of 157.20 mg/g is obtained by the Langmuir equation. The adsorption of Pb^2＋ on synthetic zeolite is a spontaneous endothermic process, and the physical adsorption is the main adsorption behavior accompanied with the chemical adsorption during the whole process.