Amphiphile grafted membranes for the separation of oil-in-water dispersions.

Perfluorinated end-capped polyethylene glycol surfactants were covalently attached to fritted glass membranes as a means to improve the separation of oil-in-water emulsions. Hexadecane was used as representative oil for the oil-in-water emulsions; membrane pore size was varied between 10 and 174 microm. Membranes were characterized with respect to contact angle, permeability of bulk fluids, and separation efficiency. Performance was compared to similar metrics applied to unmodified membranes. Modified membranes demonstrated static hexadecane contact angles which were higher than static water contact angles converse to their unmodified counterparts. The relative hydrophilicity and corresponding oleophobicity of the modified membranes resulted in greater water permeability as compared to hexadecane permeability. The presence of the perfluorinated constituent of the amphiphile retarded the flow of hexadecane. For modified membranes, suspended hexadecane coalesced at the membrane surface, was undercut by water, and floated to the surface such that only trace amounts of oil were present in the permeate. Therefore, modified membranes resisted fouling from oil due to the self-cleaning properties of the attached amphiphile.