Testing the applicability limits of a membrane distillation process with ceramic hydrophobized membranes: The critical wetting temperature

The new concept of the critical wetting temperature (TC wetting) of a hydrophobic membrane is introduced. It represents the maximum temperature at which a hydrophobic membrane can operate in no-wetting conditions with a specific liquid. The concept relies on the theoretical premises of the Laplace-Young equation. The existence of the critical wetting temperature is experimentally documented for the case of carbon-based titania membranes hydrophobized with FAS, by measuring the minimum Liquid Entry Pressure values as a function of temperature, in the range from 20 °C to 136 °C. In that case, the TCwetting was obtained close to 130 °C with pure water. The new parameter should be included in the membrane characterization protocols, since the evaluation of TC wetting is crucial to define which are the applicability limits of a membrane contactor. In alternative to various LEP measurements as a function of temperature, the measure of the minimum Liquid Entry Temperature at very low pressures can represent a more efficient method for the TCwetting evaluation.