(752c) Separation of Oil-in-Water Emulsions Stabilized By Different Types of Surfactants Using Electrospun Fiber Membranes with Surface Modification

The compositions and properties of discharged oil-in-water emulsions in industry vary widely according to their sources. Such variety poses a challenge for membrane separations. Electrospun fiber membranes have gained attention in emulsion separation due to their high permeability and improved robustness against fouling, but the interaction between the emulsion and the membrane, and the fouling mechanism that results, remains unclear. Therefore, this work seeks to understand membrane-foulant interactions and fouling mechanisms, and to develop novel membranes through surface modification to reduce the adverse effects of membrane fouling.

Electrospun polyamide membranes were challenged by model emulsions of dodecane stabilized by anionic, cationic, non-ionic and zwitterionic surfactants, in both dead-end and cross-flow filtration configurations. Analysis of permeate flux and oil rejection revealed that the types of surfactants influenced the membrane fouling in both dead-end and cross-flow systems but in different ways. Fouling in dead-end filtration was found to be a function of the electrostatic interactions between the oil droplets and the membrane, while fouling in cross-flow filtration was mainly determined by the hydrophilic/hydrophobic interactions due to the adsorption of surfactants at the interfaces. Blocking filtration models were used to corroborate these findings and to illustrate the transition between modes of fouling in dead-end filtration.

In order to modify the membrane-foulant interactions and thereby enhance separation performance for specific types of oil-in-water emulsions, surface modification on the electrospun polyamide membranes was performed by plasma treatment followed by deposition of a polycationic branched polyethylenimine from solution. The permeate fluxes of the modified membranes were shown to improve when the membrane was oppositely charged to the emulsified oil droplets, while retaining the oil rejection. Membrane fouling was successfully reduced .