Standardizing practices and flux predictions in membrane science via simplified equations and membrane characterization

The development of membranes and membrane-based separation processes should be accompanied by a standardization of the protocols applied for membrane characterization and for data analysis. Here, streamlined equations for the estimation of the water flux and of the observed salt permeability coefficient in pressure-driven processes deploying dense membranes are presented. Also, a protocol for the experimental characterization of the transport properties of dense membranes is presented and the results are validated against the proposed equations. The proposed water flux equation is algebraic, whereas the ordinary equation needs to be solved iteratively. Moreover, in contrast to the traditional expression for the solute transport coefficient, which requires estimation of the concentration polarization, the respective equation proposed in this study only requires bulk parameters. Dimensionless variables for water flux, driving pressure, and mass transfer are introduced, and a filtration efficiency is defined, a useful parameter in terms of process design.