Development of functionalized doped carbon nanotube/polysulfone nanofiltration membranes for fouling control

This work describes the fabrication of nitrogen doped and phosphorus doped carbon nanotube (fP‐CNT and fN‐CNT)/polysulfone blend membranes via a phase inversion method. The structural morphology, hydrophilicity, rejection, and permeability properties of the blend membranes were found to be dependent on the amount and type of functionalized CNTs (fCNTs) incorporated (i.e., fN‐CNTs, fP‐CNTs). The results showed that PSf membranes modified with P‐ or N‐doped CNTs have significantly improved hydrophilicity, thermal stability, water uptake, and surface charge compared to membranes modified with pristine fCNTs. Scanning electron microscopy studies demonstrated that the addition of the doped CNTs resulted in the formation of ‘finger‐like’ structures subsequently leading to increased membrane porosities and pore sizes. Thus, doped CNTs imparted on the transport mechanism of the parent membranes resulting in enhanced flow rates and better selectivity. This increase could be due to a combination of steric limitations from the carboxylic functional groups present in their surfaces leading to electrostatic repulsions between functional groups present in the membranes and the humic acid molecules.