聚偏氟乙烯共混改性膜对Zn(Ⅱ)吸附性能的研究

Adsorption Characteristics of Zn(Ⅱ) Ion onto the Polyvinylidene Fluoride Blending Modified Membrane

应用热引发聚合和相转移技术,制备了具有离子交换性能的聚偏氟乙烯共混改性膜。采用XPS、SEM和FTIR表征了PVDF共混改性膜的结构和组成,测定了共混改性膜的零电荷点(pHpzc),分析了共混改性膜对水溶液中Zn(Ⅱ)的吸附性能,研究了PVDF共混改性膜对Zn(Ⅱ)的吸附热力学和吸附动力学。结果表明,动力学吸附过程符合准二级动力学方程,等温吸附过程符合Langmuir模型。吸附过程的平均吸附能为8～16kJ/mol,表明该吸附过程为离子交换反应。热力学参数ΔG0<0、ΔH0>0、ΔS0>0,证实了吸附过程为自发的吸热过程。PVDF共混改性膜经吸附/脱附4次循环后,对水体中Zn(Ⅱ)吸附量大于0.005mg/cm2,脱附率超过95%。

A novel polyvinylidene fluoride blending modified membrane with ion-exchanging property, was prepared using thermally induced polymerization technique and phase inversion blending process. The blending modified membrane was characterized using XPS, SEM, FTIR, and point of zero charge measurement. The adsorption property, the adsorption isotherm and the batch sorption kinetics of Zn（Ⅱ） ions by the blending modified membrane were studied. The results indicated that the adsorption processes for Zn（Ⅱ） are found to follow the pseudo-second-order kinetics equation. The isotherm of adsorption of the heavy metals by the modified membrane is good agreement with that of Langmuir isotherm model. The values of the mean free energies of the adsorption process are found to be between 8 and 16 kJ/mol, which shows that the adsorption mechanism of the PVDF blending modified membrane is an ion-exchange process. The value of △H^0 is 〉0,△G^0 is 〈0, and △S^0 is 〉0, which shows that the adsorption of the modified membrane is a spontaneous and endothermic process. The experimental data also show that the PVDF modified membrane possesses an excellent adsorption/desorption property, the adsorption capacity of Zn（Ⅱ） onto the modified membrane is more than 0.005 mg/cm^2, and its desorption efficiency is still beyond to 95%, after four adsorption/desorption processes.