Miao Rui, Wu Ying, Wang Pei, Wu Gongzheng, Wang Lei, Li Xingfei, Wang Jiaxuan, Lv Yongtao, Liu Tingting
Key Laboratory of Membrane Separation of Shaanxi Province, Xi'an University of Architecture and Technology, Xi'an 710055, China E-mail:
Water Sci Technol. 2018 May;77(9-10):2265-2273. doi: 10.2166/wst.2018.141.
To reveal the mechanisms of the influence of Ca on membrane fouling with humic acid (HA), the adhesion forces of HA with both other HA molecules and the membrane, the HA fouling layer structure, HA fouling experiments, and the HA rejections at a wide range of Ca dosages were investigated. The results indicated that the effect of Ca on HA fouling can be divided into three stages. At lower ionic strength (IS) of CaCl, the change in electrostatic forces is the main factor in controlling HA fouling behavior; i.e., increasing Ca dosages resulted in more serious membrane fouling. When the IS of CaCl reached 10 mM, HA aggregates became the dominant factor in the fouling process, which could result in a porous fouling layer accompanied by less membrane fouling. Interestingly, much weaker membrane fouling was observed when the IS increased to 100 mM and the HA rejection began to decline. This was because a stronger hydration repulsion force was generated, which could weaken the compactness of the fouling layer and the adhesion forces of HA with both the membrane and HA, while enabling smaller-sized HA to pass more easily into the permeate, which led to less membrane fouling and a lower HA rejection.
为揭示钙对腐殖酸（HA）膜污染的影响机制，研究了HA与其他HA分子及膜之间的粘附力、HA污染层结构、HA污染实验以及在不同钙投加量下的HA截留率。结果表明，钙对HA污染的影响可分为三个阶段。在氯化钙离子强度（IS）较低时，静电力的变化是控制HA污染行为的主要因素，即增加钙投加量会导致膜污染更严重。当氯化钙的IS达到10 mM时，HA聚集体成为污染过程中的主导因素，这可能导致形成多孔污染层，同时膜污染程度降低。有趣的是，当IS增加到100 mM且HA截留率开始下降时，观察到膜污染程度明显减轻。这是因为产生了更强的水化排斥力，它可以削弱污染层的致密性以及HA与膜和HA之间的粘附力，同时使较小尺寸的HA更容易进入渗透液，从而导致膜污染减轻和HA截留率降低。
