Delft University of Technology, P.O. Box 5048, 2600 GA Delft, The Netherlands.
Water Res. 2011 Dec 1;45(19):6289-300. doi: 10.1016/j.watres.2011.08.004. Epub 2011 Sep 8.
This paper investigates the impact of the ionic environment on the charge of colloidal natural organic matter (NOM) and ultrafiltration (UF) membranes (charge screening effect) and the calcium adsorption/bridging on new and fouled membranes (calcium bridging effect) by measuring the zeta potentials of membranes and colloidal NOM. Fouling experiments were conducted with natural water to determine whether the reduction of the charge screening effect and/or calcium bridging effect by backwashing with demineralized water can explain the observed reduction in fouling. Results show that the charge of both membranes and NOM, as measured by the zeta potential, became more negative at a lower pH and a lower concentration of electrolytes, in particular, divalent electrolytes. In addition, calcium also adsorbed onto the membranes, and consequently bridged colloidal NOM and membranes via binding with functional groups. The charge screening effect could be eliminated by flushing NOM and membranes with demineralized water, since a cation-free environment was established. However, only a limited amount of the calcium bridging connection was removed with demineralized water backwashes, so the calcium bridging effect mostly could not be eliminated. As demineralized water backwash was found to be effective in fouling control, it can be concluded that the reduction of the charge screening is the dominant mechanism for this.
本文通过测量膜和胶体天然有机物 (NOM) 的 ζ 电位，研究了离子环境对胶体天然有机物 (NOM) 和超滤 (UF) 膜的电荷（电荷屏蔽效应）以及新膜和污染膜上的钙吸附/桥接（钙桥接效应）的影响。通过使用天然水进行污染实验，确定通过用去离子水反冲洗来降低电荷屏蔽效应和/或钙桥接效应是否可以解释观察到的污染减少。结果表明，通过 ζ 电位测量的膜和 NOM 的电荷在较低 pH 值和较低电解质浓度下变得更负，特别是二价电解质。此外，钙也会吸附在膜上，通过与官能团结合，从而桥接胶体 NOM 和膜。通过用去离子水冲洗 NOM 和膜，可以消除电荷屏蔽效应，因为建立了无阳离子的环境。然而，用去离子水反冲洗只能去除有限量的钙桥接连接，因此钙桥接效应大部分不能消除。由于发现去离子水反冲洗在控制污染方面非常有效，可以得出结论，降低电荷屏蔽是主要机制。
