Control of organic and surfactant fouling using dynamic membranes in the separation of oil-in-water emulsions

A superhydrophilic membrane with rough and hierarchical structures is possibly fouled by surfactant-stabilized oil and organic foulants, because these foulants could not be hindered by the water layer formed on superhydrophilic membrane surface. A dynamic membrane was possibly an effective method to address this fouling problem.A microfiltration membrane, a nanofiber membrane, and a dynamic membrane were used for the separation of surfactant-free emulsions, surfactant-stabilized emulsions, and the surfactant-stabilized emulsions containing typical organic foulants. The oil rejection and membrane fouling were compared.The microfiltration membrane, nanofiber membrane, and dynamic membrane had high resistances to the fouling by surfactant-free emulsions because these membranes were underwater superoleophobic. However, these membranes showed low resistances to the fouling by surfactant-stabilized oil droplets and organic foulants. For the dynamic membrane, the oil droplets and organic foulants trapped in the separation layer could be readily removed in the detachment-washing-recoating steps; therefore, almost no physically irreversible fouling was observed in the multi-cycle filtration. With the size distributions of oil droplets in the emulsions and the particle of the dynamic membrane, the rejection of oil by the dynamic membrane could be calculated by simply assuming that the particle was spherical, uniform, and tightly packed.