Measuring hydraulic layer resistance and correlated effects in colloidal fouling of salt-retaining membranes
Measuring hydraulic layer resistance and correlated effects in colloidal fouling of salt-retaining membranes
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DOI：
10.2166/ws.2016.181
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发表时间：
2017-07-01
影响因子：
--
通讯作者：
Gimbel, R.
中科院分区：
文献类型：
--
作者：
Keller, M.;Panglisch, S.;Gimbel, R.
胶体污染是膜基海水淡化工艺效率降低的主要原因之一。水力、渗透和电动等阻力机制的同步以及众多的耦合效应使得分析它们各自对污染程度的贡献变得复杂。一种新的测量方法，使用死角过滤测试池，可以完全做到这一点，而不考虑任何同时发生的浓度极化现象。第一个结果表明，完全发育的胶体层的水力阻力并不完全取决于其成分的物理化学性质，而似乎强烈依赖于其形成的特定方式（例如，在层堆积或不同粒径的过滤过程中普遍存在的离子强度）。这种依赖时间的效应在很大程度上是不可逆的，因此很可能是由于污染层结构的持续变化。一个次要的可逆离子强度效应也可以证明。无论离子强度是增加还是减少，这种影响的程度是相同的。结果进一步表明，通常应用的模型，如Kozeny-Carman方程，缺乏一个与粒径相关的参数，该参数导致胶体污染层阻力随着污染物粒径的减小而不成比例地降低。
Colloidal fouling is one of the main reasons for the reduced efficiency of membrane-based water desalination processes. The synchrony of several resistance mechanisms like hydraulic, osmotic, and electro-kinetic as well as numerous coupling effects complicate the analysis of their individual contributions to the fouling extent. A new measuring approach using a dead-end filtration test-cell allows exactly this, irrespective of any simultaneously occurring concentration polarization phenomena. First results show that the hydraulic resistance of a fully developed colloidal layer is not exclusively determined by the physicochemical properties of its constituents but seems to be strongly dependent on the specific way of its formation (e.g. ionic strength prevailing during layer build-up or filtration sequence of different particle sizes). This time-dependent effect is largely irreversible and therefore most likely due to persistent changes in fouling layer structure. A minor reversible ionic strength effect could also be demonstrated. The extent of this effect is identical irrespective of whether the ionic strength is increased or decreased. Results further indicate that commonly applied models like the Kozeny-Carman equation are lacking a size-dependent parameter that causes a disproportionate decrease of colloidal fouling layer resistance with decreasing foulant particle size.