Understanding the influences of cations on membrane fouling was important to improve the performance of membrane filtration system, however, opposite conclusions were made in different studies. Meanwhile, although the influences of cation concentration have been studied extensively, few attentions have been paid to the cation valence. To clarify it, the effects of typical cations on membrane fouling and cleaning, as well as the related mechanisms were investigated systemically in this study. K⁺ and Ca²⁺ were chosen as the representative cations, and humic acid (HA) was chosen as the membrane foulants. The results demonstrated Ca²⁺ promoted the formation of reversible fouling, meanwhile higher removal efficiency of HA could also be achieved with the assistance of filtration cake containing HA + Ca²⁺. However, K⁺ led to the formation of more recalcitrant irreversible fouling. By comparing the concentration of cations in feed and permeate, analyzing the influence of cations on size of HA flocs, and the detailed SEM, AFM and TEM observation, it could be found that different mechanisms dominated the interaction between cations and HA. The bridging effect induced by Ca²⁺ attributed to the extension of HA molecules, while the electrostatic shielding effect induced by K⁺ led to the compression of them. Moreover, the different characteristics of hydrated Ca²⁺ and K⁺ also contributed to the different structures of foulant layers formed by HA + Ca²⁺ and HA + K⁺. Given the abundance of K⁺ and Ca²⁺ in natural water, results of this study can provide valuable advice for practical membrane filtration process.

了解阳离子对膜污染的影响对于提高膜过滤系统的性能很重要，但是，在不同的研究中却得出相反的结论。同时，尽管已经广泛研究了阳离子浓度的影响，但是对阳离子价数的关注很少。为了澄清这一点，本研究系统地研究了典型阳离子对膜结垢和清洁的影响以及相关机理。选择K ⁺和Ca ²⁺作为代表性阳离子，选择腐殖酸（HA）作为膜污染物质。结果表明Ca ²⁺促进了可逆结垢的形成，同时借助含HA + Ca ^2+的滤饼也可以实现更高的HA去除效率。但是，K ⁺导致形成更顽固的不可逆结垢。通过比较进料和渗透液中阳离子的浓度，分析阳离子对HA絮凝物尺寸的影响，以及详细的SEM，AFM和TEM观察，可以发现不同的机理主导了阳离子与HA的相互作用。Ca ²⁺引起的桥连效应归因于HA分子的延伸，而K ⁺引起的静电屏蔽效应导致其压缩。此外，水合钙的不同特征²⁺和K ⁺也有助于由HA + Ca ²⁺和HA + K ⁺形成的污垢层的不同结构。考虑到天然水中K ⁺和Ca ²⁺的含量丰富，这项研究的结果可为实际的膜过滤过程提供有价值的建议。