High Pressure Resistance in Omniphobic Distillation Membranes with Re-entrant Nanostructures

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Distillation of low-surface-tension liquids is challenging due to membrane wetting.
• High applied pressures typically exacerbate wetting issues in traditional membranes.

Purpose of the Study:

• To develop pressure-resistant omniphobic membranes capable of stable distillation of low-surface-tension liquids.
• To validate wettability theory under extreme pressure conditions.

Main Methods:

• Synthesized omniphobic membranes by grafting re-entrant nanostructures onto porous alumina, followed by hydrophobic modification.
• Tested membrane performance using water and a 15 wt% ethanol-water mixture, measuring liquid entry pressure and applied pressure resistance.
• Employed simulations to understand the role of re-entrant structures in enhancing wetting resistance.

Main Results:

• Developed membranes with a high liquid entry pressure of 36.2 bar for water.
• Achieved stable distillation of a low-surface-tension ethanol-water mixture at applied pressures up to 15.5 bar.
• Demonstrated over 97% salt rejection during pressure-driven distillation.
• Simulations showed re-entrant structures increased wetting pressure by 220% for low-surface-tension liquids.

Conclusions:

• Successfully demonstrated the first distillation membranes operating with low-surface-tension liquids under high applied pressures.
• The developed membranes offer a robust solution for challenging liquid separations.
• The study validates theoretical models of wettability under extreme pressure conditions.