Surface chemistry, topology and desalination performance controlled positively charged NF membrane prepared by polydopamine-assisted graft of starburst PAMAM dendrimers

A novel and facile method to prepare surface chemistry, topology and separation performance controlled positively charged nanofiltration membranes by polydopamine-assisted grafting of starburst PAMAM onto polyethersulfone (PES) membranes was introduced. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM), zeta potential and water contact angle measurements were applied to characterize the morphology and chemical composition changes of the resultant membranes. The result of the salt rejections followed the sequence: R (MgCl2) > R (MgSO4) > R (NaCl) > R (Na2SO4), which indicated a PAMAM grafting membrane with a positively charged surface. The MgCl2 rejections of the resultant membrane increased with increasing PAMAM generation numbers (G0, G1 and G2) and reached 83.67%, 90.53% and 93.15%, respectively. The resultant membrane possessed a good structural stability and anti-fouling properties, which were determined by the long-term testing. This facile, mild and highly controllable polydopamine-assisted PAMAM grafting modification may find broad applicability in preparing positively charged NF membranes with tunable properties to meet potential needs.