(589d) Controlling Membrane Flux By Changing the Contact Angle of Liquids

This research presents the quantitative relationship between flux through membranes and the contact angles of permeating liquids on the solid material of which the membranes are made. We chose the membrane materials so that the contact angle of water on the flat surface of the membrane materials were 40, 60, 80, and 120 degrees. The pore sizes of the membranes were kept the same at 50 μm. Membrane samples were placed at the bottom of a glass column to measure the hydraulic head at which the liquids started to penetrate/permeate. In a similar way, we measured flux through membranes with a constant hydraulic head.

We observed that the increase in the contact angles increased the height at which water started to penetrate. This result was compared with the equation which calculates the force needed to penetrate pores that accounts for the adhesion energy, Laplace pressure, and cohesion. Our results revealed that, at different contact angles, the dominating forces that controlled the permeation through membrane pores were different; cohesion of water controlled the permeation at low contact angles and adhesion between water and membrane materials controlled permeation at high contact angles. We also found that the flux was controlled by adhesion between water and membrane materials.

This signifies that permeation or flux through a membrane can be controlled in situ by controlling the contact angle of water on the membranes. We propose a novel method to control the contact angle of water in-situ as a framework for creating a new type of control valve using in situ change of contract angle.