Simplified flux prediction in direct-contact membrane distillation using a membrane structural parameter

• Membrane structural parameters were evaluated for use in predicting water flux. • Membrane constant containing non-coupled membrane properties was introduced. • Membrane constant requires simple measurements and inexpensive analytical equipment. • Membrane constant correlates well with experimental water flux. • Comprehensive collection of MD membrane properties and water fluxes made available. a b s t r a c t a r t i c l e i n f o A priori water flux prediction is desirable when conducting membrane distillation (MD) studies, however existing models are complicated with inconsistent mass transfer mechanism assumptions. To develop a simplified model that can be used to predict the relative magnitudes of water fluxes for a group of MD membranes, correlation analyses were performed between water flux and 28 structural parameters. Four parameters were found to be highly correlated with water flux: ε/δ, ε/τδ, 1/τδ, and C m. C m is a newly introduced structural parameter that contains non-coupled membrane properties but still carries the physical meaning of a relationship between δ (thickness) and ε (porosity) and is determined by simple and reliable measurements using inexpensive analytical equipment. The correlation result between water flux and C m suggests that C m is a good structural parameter for MD flux prediction. The flux prediction errors for membranes with pore sizes from 0.1 to 0.9 μm were generally smaller for the model developed with C m than for the dusty gas model. In addition to the new structural parameter and model, this study also makes available to the literature a detailed collection of MD membrane properties and their water flux values that will assist others in membrane selection, development, and application.