Filter paper with selective absorption and separation of liquids that differ in surface tension.

Superhydrophobic and superoleophilic filter paper was successfully prepared by treating commercially available filter paper with a mixture of hydrophobic silica nanoparticles and polystyrene solution in toluene. Applications of the filter paper in separating liquids with low surface tensions such as oil and ethanol from water were investigated in detail. The oil uptake ability of the superhydrophobic filter paper was evaluated and the results show that the filter paper can selectively adsorb oil floating on a water surface or in aqueous emulsions. Furthermore, filtration of mixtures of oil and water through the paper can reduce the water content in the oil. Additionally, the filter paper can also extract ethanol from homogeneous aqueous solution.