Effect of hydrophilization additive and reaction time on separation properties of polyamide nanofiltration membrane

Thin film composite (TFC) nanofiltration membrane can be optimized in terms of flux and rejection by controlling the hydrophilization additive [3,5-diaminobenzoic acid (BA)] content and reaction time in the interfacial polymerization (IP) process. By using the Donnan steric pore flow model (DSPFM), uncharged solute was passed through the membrane to determine the pore size (r(p)) as well as the effective thickness/porosity (Deltax/A(k)). The coating condition was related to the performance of NaCl permeation using the fitted r(p) and Deltax/A(k) data. It was found that the pore size was reduced as reaction time was increased. Cross-linking reduced the porosity of polypiperazinamide membrane but it was noticed that by adding a small amount of BA, the porosity was increased at Ion-er reaction time. A small amount of BA could increase both the flux and rejection especially at higher pressure.