Fabrication of polydopamine functionalized halloysite nanotube/polyetherimide membranes for heavy metal removal

Polydopamine modified halloysite nanotubes (HNTs) were synthesised through a one step facile procedure and employed as a well dispersed hydrophilic additive to enhance the filtration properties of polyetherimide (PEI) membranes. The nanocomposite membranes were prepared by an immersion precipitation method with different amounts of modified HNTs (MHNTs) in the casting solution. The good dispersion of MHNTs throughout the membranematrix was confirmed by elemental mapping analysis. The prepared nanocomposite membranes were extensively studied in terms of their porosity, morphology, membrane hydraulic resistance and hydrophilicity. The permeation experiments showed that the modified membranes exhibited higher water flux than a pristine PEI membrane. The antifouling and anti-biofouling behaviour of the modified membranes was investigated in detail. The results revealed that a membrane with a 3 wt% MHNT dosage showed a higher Fouling Resistance Ratio (FRR) of 74.5% with reversible membrane fouling of 64.3%. Moreover, the membrane showed excellent resistance to microbial growth on the membrane surface. The well performing membrane was subjected to heavy metal ion rejection. Results indicated that membranes had the capacity to adsorb Pb2+ and Cd2+. Overall, PEI-MHNTs nanocomposite membranes could have great potential to improve antifouling, anti-biofouling and filtration properties.