Fouling-resistant membranes for separation of oil-in-water emulsions

Separation by membrane technology of oily wastewater, especially emulsified oil/water mixtures, has become a topic of intensive study in recent years, and membrane fouling remains a challenge. In this work, porous polycarbonate membranes were coated with poly(diallyldimethylammonium chloride)/polystyrene sulfonate (PDDA/PSS) multilayers via the facile layer-by-layer deposition technique to improve their fouling resistance for separation of oil-in-water emulsions stabilized by ionic surfactants. The permeation flux for the virgin membrane was found to decrease by ∼90% in 10 cycles due to fouling. The membranes coated with PSS-capped PEMs were used to separate emulsions stabilized by sodium dodecyl sulfate, an anionic surfactant, whereas the ones modified with PDDA-capped PEMs were effective for separation of emulsions stabilized by cetyltrimethyl ammonium bromide, a cationic surfactant. Both retained up to 80% of their original permeation flux after 10 separation cycles. The purity of the filtrates was greater than 99.98%.