PEI modified multiwalled carbon nanotube as a novel additive in PAN nanofiber membrane for enhanced removal of heavy metal ions

Both multiwalled carbon nanotubes (MWCNTs) and electrospun nanofibers are ideal nanomaterial candidates with great potential in the field of heavy metal ions remediation. In the present study, the advantages of these two nanomaterials were combined with electrospinning method to prepare a novel nanocomposite membrane (NCM) containing improved physical properties and enhanced removal efficiency for metal ions. Modified MWCNTs were initially fabricated by reacting MWCNT-COOH with polyethylenimine (PEI), which was further embedded within polyacrylonitrile (PAN) nanofibers through electrospinning. The structure, morphology and physical property of prepared MWCNT-PEI and NCM (MWCNT-PEI/PAN) were carefully characterized with FTIR, SEM, TEM, mechanical test and contact angle measurements. Compared with plain PAN membrane, the prepared NCM possesses higher mechanical strength and improved hydrophilicity, resulting in high permeation and filtration efficiency. Batch adsorption experiments demonstrated that MWCNT-PEI/PAN nanocomposite membrane exhibited higher adsorption amount for Pb2+ and Cu2+ ions compared with other nanocomposite membranes. Additionally, the adsorption processes were elaborated to follow pseudo-second-order kinetic and Langmuir isotherm, indicating the PEI groups embedded in the NCM was the main adsorption active site and chemisorption was the mainly mechanism for the uptake of heavy metal ions. The dynamic adsorption results proved that the designed NCM exhibited improved rejection ability to metal ions with a water flux at 145.8 L m−2 h−1 under 0.2 bar pressure. The NCM could treat 240 mL and 170 mL of 40 mg/L Cu2+ and Pb2+ solution while maintaining a drinking water standard of 1 mg/L and 10 µg/L, respectively. The improved membrane performance along with the excellent heavy metal removal efficiency suggests that this novel prepared NCM possess promising potential for heavy metal contaminated water treatment through the process of membrane adsorption.