Synthesis-structure-performance relationships of nanocomposite polymeric ultrafiltration membranes: A comparative study of two carbon nanofillers

Many nanoscale fillers have been impregnated in polymeric ultrafiltration membranes in order to augment performance, but their effects on membrane formation, structure, and performance remain fragmentally and poorly understood. In this work, we comparatively studied the effects of two carbon nanofillers (i.e., graphene oxide (GO) and carboxylic-functionalized carbon nanotube (c-CNT)) and established a coherent understanding of the synthesis-structure-performance relationships of such nanofiller-impregnated ultrafiltration membranes. Our results show that the morphological factor, as a result of nanoparticle properties, in addition to thermodynamic instability and rheological hindrance, is an important factor to consider when evaluating the effects of (carbon) nanofiller on membrane formation. Further, we addressed the discrepancy previously observed in rejection performance change after nanofiller addition, and demonstrated that the main benefits of adding carbon nanofillers exist in the enhancement of rejection of negatively charged molecules with increased permeability at low nanofiller mass loading. Our research findings bridge critical knowledge gaps, and provide mechanistic insights into the role and application of nanofillers in membranes.