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| Analysis of interfacial interactions in reverse osmosis membrane fouling by humic acid Effect of solution pH |
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Abstract The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) approach was applied for better understanding of the basic interfacial interactions (i.e. van der Waals interaction, electrostatic interaction and acid-base interaction) involved in reverse osmosis(RO)membrane fouling by humic acid at different pHs. Based on the theoretical calculations with three representative RO membranes, the electrostatic interaction was found to be negeligible in membrane fouling. The van der Waals interaction favored fouling, whereas acid-base interaction could prevent it. The contribution of van der Waals interaction was higher in the cohesion stage than that in the adhesion stage. The acid-base interaction was dominant in both stages. Membrane fouling became less serious as solution pH increased. The surface free energy was affected by solution pH mainly via the alternation of acid-base energy. Correlation analysis of the corresponding fouling data proved that XDLVO approach could successfully describe the characteristics of RO membrane fouling by humic acid and quantitatively evaluate the involved interfacial interactions. The contact angle of RO membrane measured by pure water turned out to be an inappropriate parameter for accurate prediction of membrane fouling.
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Received: 02 September 2010
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