聚吡咯膜电极选择性分离离子研究

Selective separation of ions by polypyrrole membrane electrodes

电渗析作为一种高效且环境友好的电驱动膜分离技术,可以在外加直流电场的驱动下实现离子的选择性分离,被广泛应用于水处理与资源回收,其中离子交换膜是选择性分离的关键.本研究采用电化学沉积法成功制备了聚吡咯/对甲苯磺酸(PPy/pTS)膜电极,发现其可在0.4 V与-0.8 V(vs.Ag/AgCl)下分别发生氧化和还原反应,并伴随着阴离子的嵌入和脱出,从而实现阴离子的富集与分离.采用PPy/pTS膜电极建立了膜电极电渗析器并进行Cl^(-)和SO_(4)^(2-)的分离.研究发现低pTS的掺杂量有助于提高离子分离性能,pTS浓度为0.1 mol·L^(-1)时,接收液Cl-和SO_(4)^(2-)的浓度分别为0.59 mmol·L^(-1)和0.03 mmol·L^(-1),Cl-/SO_(4)^(2-)分离因子可以达到13.92.此外,优化PPy/pTS膜电极电化学沉积时间.发现沉积时间过短(30 min)时的PPy/pTS膜电极不够致密、无法阻止离子自由扩散,而沉积时间过长(1 h)时PPy/pTS时膜电极离子扩散量低且分离效果不佳,经实验确定45 min为最佳电化学沉积时间.

As an efficient and environmental-friendly electrical membrane separation technology,electrodialysis can realize the selective separation of ions driven by an electric field.Electrodialysis is widely used in water treatment and resource recovery,in which the selective permeability of the ion exchange membrane is the key factor.In this study,a polypyrrole/p-toluenesulfonic acid(PPy/pTS)membrane electrode was successfully prepared by using electrochemical deposition.The PPy/PTS membrane electrode can be oxidized and reduced at 0.4 V and-0.8 V(vs.Ag/AgCl),respectively,accompanied by the insertion and deinsertion of anions,which realized the enrichment and separation of anions.The membrane electrode electrodialyzer was established with the PPy/pTS membrane electrode for the separation of Cl^(-)and SO_(4)^(2-).The results showed that the low doping amount of pTS contributed to improve the ion separation performance,and the concentration of Cl-and SO_(4)^(2-)in the receiving solution were 0.59 and 0.03 mmol·L^(-1),respectively.The Cl-/SO_(4)^(2-)separation factor could reach 13.92.In addition,the deposition time of the PPy/pTS membrane electrode was optimized.It was found that the PPy/pTS membrane electrode was not dense enough to prevent the free diffusion of ions when the deposition time was 30 min,and the membrane electrode ion diffusion rate was low and the separation performance was poor when the deposition time was prolonged to 1 h.Thus,45min was considered to be the optimized electrochemical deposition time.