Restructuring the surface of polyurethane resin enforced filter media to separate surfactant stabilized oil-in-water emulsions via coalescence

Reported here is a facile resin emulsification method of treating polyurethane enforced filter media by controlling the initial level of solvent volatilization for resin solidification. The treated media are endowed with varying degrees of lipophilicity as determined by their lipophilic to hydrophilic (L/H) values. An optimized treatment condition was pinned for coalescence separation of surfactant-stabilized oil-in-water emulsions using a surfactant free emulsion as the bench mark. The starting separation efficiency was found to depend on the type of surfactant involved in the order of non-ionic surfactant Tween 80 > cationic surfactant cetyl trimethyl ammonium bromide (CTAB) > anionic surfactant sodium dodecyl benzene sulfonate (SDBS). Quartz crystal microbalance (QCM) experiments showed that Tween 80 had the largest adsorption on the polyurethane coating, while least adsorption occurred to SDBS, and mediocre adsorption to CTAB. However, Tween 80 resulted in the lowest time-weighted averaged efficiency as compared to the other surfactants that barely caused any efficiency changes with filtration time. To make the resin emulsification treatment more environmental friendly, more polar solvents were tested, and ethanol was identified as a good alternative to isopropanol.