A pH-responsive smart surface for the continuous separation of oil/water/oil ternary mixtures

To handle the serious issue of increasing oil spill accidents, many strategies have been proposed to either clean spilt oil or separate water/oil mixture. Especially, superhydrophilic/underwater superoleophobic smart materials have recently shown advantages in overcoming problems of oil blocking and water barriers during conventional oil/water-separating process of oil-rich mixtures with superhydrophobic/superoleophilic materials. However, to the best of our knowledge, no prior reports have detailed smart materials with the wetting properties of superhydrophobic/superoleophilic that can be applied in continuous in situ separations of oil/water/oil ternary mixtures, which are common in practical oil spill cases. Herein, we describe the fabrication and efficacy of a pH-responsive smart device for continuous in situ separations of such oil/water/oil ternary mixtures without the need for ex situ treatments. In air, the superhydrophobic/superoleophilic surface of the device allowed dichloromethane to permeate through while preventing water from passing. The superhydrophilicity/underwater superoleophobicity of the device surface following alkaline treatments prevented the passage of hexane while allowing water to penetrate the device.