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Thin film nanocomposite membranes have become a feasible technology for heavy metal wastewater treatment. However, how to enhance the dispersibility and compatibility of nanomaterials in the selective layer is an important issue to improve the membrane performance of heavy metal removal. In this study, silica-poly(ionic liquid) nanoparticles were incorporated in the selective layer of TFN membranes. 1-Allyl-3-methyl imidazolium hexafluorophosphate ([AMIm]PF6) was selected to modify silica (SiO2) particles. The formed poly([AMIm]+) brushes provided charge properties to enhance dispersibility and organic part to improve compatibility in the polyamide layer of NF membranes. The resultant TFN membranes incorporated with SiO2-[AMIm]PF6 particles exhibited an increment of 34% water permeation and 41.6% MgCl2 rejection. Moreover, with an average rejection improvement of around 15% for heavy metal ions at pH = 5–6, the SiO2-[AMIm]PF6/PA membrane showed its superiority beyond the PA membrane. The electropositivity and microporous structure of the SiO2-[AMIm]PF6 particles enhanced their dispersibility and compatibility in the polyamide layer. Meanwhile, the proper pore size and structure of the SiO2-[AMIm]PF6 particles contributed to the channels for water transport and the sieving effect for most heavy metal ions. This work may facilitate the applications of TFN membranes in heavy metal wastewater treatment to alleviate the “trade-off” phenomenon.

Electrically conductive membranes have been regarded as a new alternative to overcome the crucial drawbacks of membranes, including permeability-selectivity trade-off and fouling. It is still challenging to prepare conductive membranes with good mechanical strength, high conductivity and stable separation performance by reliable materials and methods. This work developed a facile method of simultaneous phase inversion to prepare electrically conductive polyethersulfone (PES) membranes with carboxylic multiwalled carbon nanotubes (MWCNT) and graphene (Gr). The resultant MWCNT/Gr/PES nanocomposite membranes are composed of the upper MWCNT/Gr layer with good conductivity and the base PES layer providing mechanical support. MWCNT as nanofillers effectively turns the insulting PES layers to be electrically conductive. With the dispersing and bridging functions of Gr, the MWCNT/Gr layer shows an enhanced electric conductivity of 0.10 S/cm. This MWCNT/Gr/PES membrane in an electro-filtration cell achieves excellent retention of Cu(II) ions up to 98 % and a high flux of 94.5 L m−2∙h−1∙bar−1 under a low driven-pressure of 0.1 MPa. The conductive membrane also shows improved anti-fouling capability during protein filtration, due mainly to the electrostatic repulsion and hydrogen evolution reaction on the electrode. This facile strategy has excellent potential in electro-assistant membrane filtration for fouling control and effective separation.