Novel binding procedure of TiO2 nanoparticles to thin film composite membranes via self-polymerized polydopamine

This study presents a novel and versatile approach to robustly bind TiO2 nanoparticles on thin film composite (TFC) membranes by using polydopamine, which is capable to self-polymerize on membranes as well as on the surfaces of nanoparticles. The traditional self-assembly method is used as a reference. The binding performance of both methods is investigated by rinsing and wiping tests and evaluated by scanning electronic microscopy (SEM). In addition, the effects of the concentration of TiO2 nanoparticles in the suspension as well as the polymerization time of dopamine on the binding performance are studied. It was observed that, for the same modification and rinsing conditions, the polydopamine method is able to bind significantly more TiO2 on the membrane surface. According to the wiping test, the quantity of nanoparticles embedded in the polydopamine layer does not change. However, the traditional self-assembly method cannot stand the wiping force and no nanoparticles are left after wiping. The interesting hydrophilicity and the filtration performance of each modification step is further investigated. The polydopamine significantly increases the water contact angle of the polyamide thin film composite (TFC) membranes. The membranes modified by the traditional self-assembly method exhibit a significant flux loss compared to the original membranes. On the contrary, the polydopamine method can keep the membrane performance. Thus, this procedure can be considered as a novel and versatile method to bind TiO2 nanoparticles on TFC membranes, and it can be easily adapted for a variety of membranes to bind nanomaterials without a complex surface pretreatment.