Filter for Oil-Water Emulsions

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Image provided by Queen's University. Emulsions stabilized by surfactants are very difficult to separate because the emulsified droplets are very small and very stable. As such, conventional techniques such as gravity separation or skimming are ineffective. Filters can be effective if the pore size is smaller than the emulsified droplet but in this case the flux is low and the separation is so slow that it is impractical for most applications. Technology Overview This filter technology uses polymer-functionalized surfaces to first break the emulsion and coalesce the oil phase and then selectively permeate it through the filter. By applying this technology, filters with pore sizes hundreds of times larger than the emulsified droplets can be used to readily separate emulsions stabilized by either ionic or non-ionic surfactants without the use of pressure. Upon contact with the emulsion, the emulsion-breaking functionality of the filter competes with free surfactants for adsorption onto the emulsified droplets and draws them onto the surface of the filter where they coalesce locally. The coalesced oil then fills the pores of the filter and the superhydrophobic functionality of the other side selectively permeates the oil through the filter. This technology can be applied to both fabric and metal mesh filters and has been tested with a number of different oil-water emulsions.