Theoretical assessment of dilute acetone removal from aqueous streams by membrane distillation

The removal of dilute acetone from aqueous streams by air-gap membrane distillation is theoretically assessed. A combined heat and mass transfer model that includes temperature and concentration polarization effects as well as temperature and concentration variation along the module length is employed to predict the flux and selectivity of acetone under the relevant process operating conditions. Three mass transfer solutions are heeded in the model: the exact Stefan-Maxwell, the approximate Stefan-Maxwell, and the Fickian binary solution. Although, behaviorally, the three solutions exhibit the same trends, quantitatively some differences exist between the Fickian- based solution on the one hand and the Stefan-Maxwell solutions on the other hand. The exact and approximate solutions of the Stefan-Maxwell equation showed a similar capability in predicting the process achievement under all process conditions. Predictions showed that acetone selectivity and flux were strongly dependent on feed conditions and air-gap width.