Abstract:

Donnan dialysis is a selective membrane process driven by an electrochemical potential. It can be used for arsenate [As(Ⅴ)] removal from drinking water. In this study, the effects of the intermembrane As(Ⅴ) mobility, membrane affinity to As(Ⅴ), membrane effective area and its thickness on As(Ⅴ) removal kinetics were investigated based on the analysis of the process variables in an As(Ⅴ) dialytic model. The results indicated that when the rotation rate was higher than 200 r·min^-1, the intermembrane diffusion was the rate-limiting step for the As(Ⅴ) mass transfer in the Donnan dialysis process. Higher intermembrane mobility, larger membrane area and thinner membrane accelerated the As(Ⅴ) removal on the same degree. However, they did not change the residual As(Ⅴ) concentration in the feed solution at the Donnan equilibrium. The conditions of both feed and stripping solutions affected the As(Ⅴ) concentration gradient across the membrane. Besides the As(Ⅴ) flux, they also altered the Donnan equilibrium. Membrane module of the high packed density and in-situ As(Ⅴ) removal from stripping solution were proposed for the development of novel arsenic removal device based on Donnan dialysis.

Key words: dialysis, membrane, diffusion, mass transfer, arsenate, drinking water

摘要：

道南渗析(Donnan dialysis)是电化学势差驱动的选择性膜过程,可用于饮用水中砷酸根离子[As(Ⅴ)]的去除。通过对膜相As(Ⅴ)传质模型中参数的系统分析讨论了As(Ⅴ)膜相自扩散系数、膜对As(Ⅴ)的选择性、膜面积和膜厚度等对道南渗析除砷过程的影响。结果表明,当转速高于200r·min^-1时膜相传质为道南渗析除砷的速率限制步骤。提高膜相自扩散系数、增大膜有效面积、减小膜厚度能同等程度地改善As(Ⅴ)渗析传质效果,但这些参数并不影响道南平衡达到时料液中As(Ⅴ)的残余浓度。改变料液和解吸液的溶液条件直接影响膜相As(Ⅴ)浓度梯度,不仅影响As(Ⅴ)渗析通量,也会改变道南平衡。选择高填充密度的膜组件、及时去除解吸液中富集的As(Ⅴ)是提高道南渗析除砷装置运行效率的有效手段。

关键词: 渗析, 膜, 扩散, 传质, 砷, 饮用水