Thermodynamic analysis of effects of contact angle on interfacial interactions and its implications for membrane fouling control

• Total interaction energy monotonically decreases with water contact angle.
• Total interaction energy monotonically increases with glycerol contact angle.
• Water and glycerol contact angle are reliable indicators predicting interaction.
• Membrane roughness remarkably decreases interaction strength.
• Diiodomethane contact angle has minor effect on the total interaction.

Concept of hydrophobicity always fails to accurately assess the interfacial interaction and membrane fouling, which calls for reliable parameters for this purpose. In this study, effects of contact angle on interfacial interactions related to membrane fouling were investigated based on thermodynamic analysis. It was found that, total interaction energy between sludge foulants and membrane monotonically decreases and increases with water and glycerol contact angle, respectively, indicating that these two parameters can be reliable indicators predicting total interaction energy and membrane fouling. Membrane roughness decreases interaction strength for over 20 times, and effects of membrane roughness on membrane fouling should consider water and glycerol contact angle on membrane. It was revealed existence of a critical water and glycerol contact angle for a given membrane bioreactor. Meanwhile, diiodomethane contact angle has minor effect on the total interaction, and cannot be regarded as an effective indicator assessing interfacial interactions and membrane fouling.