GENERAL TREATMENT OF LIQUID-PHASE BOUNDARY-LAYER RESISTANCE IN THE PERVAPORATION OF DILUTE AQUEOUS ORGANICS THROUGH TUBULAR MEMBRANES

In the present study, pervaporation of dilute volatile aromatic solutes from water is investigated. The study draws particular attention to the importance of liquid phase boundary layer resistance on transport in the pervaporation of solutes which form highly nonideal mixtures with water. Identifying the controlling resistance is a critical factor in module design and process efficiency. The simulation procedure employed to describe solute transport was based on solving the continuity equation for the given solute. Solute diffusivity values in the aqueous phase play a crucial role in determining the theoretical fit of the experimental data. The theoretical predictions were found to correlate with the experimental data reasonably well. The dimensionless Z number was found to be a useful parameter in terms of which the experimental and theoretical results were represented. Another important parameter was identified and expressed as the dimensionless E parameter, which is the relative liquid phase resistance in relation to the membrane resistance and which represents effects due to solute/membrane interactions, the extent of solute non-ideality in the aqueous phase and membrane module dimensions. The central aim of the research study was to show that for transport processes involving a liquid phase, the liquid-phase boundary resistance is an important factor affecting the overall solute yield and process efficiency.