A dually charged nanofiltration membrane by pH-responsive polydopamine for pharmaceuticals and personal care products removal

Advantages of nanofiltration membranes are well-known in removal of trace organic pollutants such as pharmaceuticals and personal care products (PPCPs) in water. A dually charged polyelectrolyte multilayer membrane with an active skin layer was prepared by the modification of polyethersulfone (PES) ultrafiltration membrane through the layer-by-layer technique of oppositely charged polyelectrolytes of polydopamine (PDA) and quaternate chitosan (HTCC). The physicochemical properties of the nanocomposite membrane were investigated using surface morphology, hydrophilicity, surface charge and molecular weight cut off. The influence of dopamine, support salt (NaCl) concentration and self-assembled layers number was documented. The optimized membrane had a molecular weight cut off of about 935 Da and possessed a pure water permeability of 15.665L·m−2·h−1·MPa−1. The results also exhibited salt rejection ability as K2SO4 > Na2SO4 > MgSO4 > NaCl > KCl > MgCl2 at neutral pH. In addition, the optimum membrane had higher rejection to atenolol (ATE), carbamazepine (CBZ) and ibuprofen (IBU) at 76.22%, 87.29% and 89.85%, respectively. Moreover, the retention of ATE and CBZ could be increased to 81.67% and 92.50% via adjusting pH, demonstrating that the surface of modified membrane had dually charged properties.