The fouling behaviour of a reverse osmosis (RO) membrane by three types of surfactants and a countermeasure to the fouling were studied. The filtration experiments showed that the permeability during filtration depended on the surfactant concentration and the charge of surfactant. Higher surfactant concentration deteriorated the permeability due to the concentration polarization. A negatively charged anionic surfactant, sodium lauryl sulfate (SLS), had less influence on the permeability than cationic and non-ionic surfactants. As the RO membrane used in this research had a hydrophilic and negatively charged membrane surface, adsorption of the anionic surfactant was prevented by the electrostatic force between the membrane surface and the hydrophilic group of the surfactant. To control the fouling by the cationic and non-ionic surfactants, addition of SLS to the surfactant solution was tested. Consequently, the addition of excess SLS changed the surface charge of aggregates into more negative value and the permeability during filtration was successfully improved. Furthermore, the drop in pure water permeability after filtration was not observed by the addition of excess SLS. Thus, the modification of charge of solutes to the same sign of the membrane surface charge was thought to be useful to control a membrane fouling by surfactants.

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