Anion rejection in a nitrate highly rejecting reverse osmosis thin-film composite membrane

A composite polyamide/polysulfone thin-film membrane with a high rejection towards nitrate ions has been selected to develop a reverse osmosis denitrification treatment of natural water polluted by inorganic nutrients. The model was chosen to characterize the membrane under a broad range of different operating conditions (temperatures, pressures, recycling rates and electrolyte concentrations). The Kimura-Sourirajan model can simplify the experimental work needed to select the membrane suitable for the studied process. Numerical equations to calculate the main transport parameters of the membrane (pure water permeability, mass transfer coefficients and solute transport parameter) have been obtained by a multiple regression procedure and checked with NaCl, NaNO3, KCl and K2SO4 solutions.