Comprehensive characterization of commercial nanofiltration membranes


This paper presents a comprehensive characterization study of NF 90 (Filmtec), NF 270 (Filmtec), NF 2 (Sepro), and NF PES 10 (Microdyn-Nadir) membranes by their morphology, charge, and separation performance parameters. Extensive investigations of the relations between membrane performance and membrane charge/morphological properties were performed by various measurement methods and active layer mass transport modelling. For this purpose, a broad experimental program was exerted with saccharides and polyethylene glycol at various pressures and with single salt solutions of NaCl, CaCl2, Na2SO4, and MgSO4 at various concentrations. pH effect on membrane performances was investigated as well. A Fortran program code of a hydrodynamic model was developed in order to determine the pore sizes of the membranes using the experimental data with organics. In addition, an equation-based software, COMSOL Multiphysics, was utilized for the modelling with salt solutions. This eliminated the effort demanding program code writing for concentration and potential differential equations derived from extended Nernst-Planck (ENP) equation, which is a common method in many publications. By this model, transport phenomena inside the membrane, relation between the membrane performance and its charge, as well as performance prediction of the membranes could be quested in detail.
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