Combinational strategy of chemical graft and layer-by-layer assembly of novel nanocomposite membranes fabrication for heavy metal ion capture

Heavy metal ions (HMI), a non-degradable toxic substance, has raised widespread concerns in water purification. Membrane separation is a considerable and promising technology for removing HMIs from water, due to its environmentally friendly, clean and highly effective. This study reported a functional composite ultrafiltration membrane prepared from natural biomolecules ε-Poly-L-lysine hydrochloride (PLL), sodium lingo sulfonate (SLS) or sodium alginate (SA) based on the combination strategy of chemical graft and layer-by-layer assembly. The fabricated membrane exhibited a high pure water flux (2957 L·m −2 ·h −1 ), high capture efficiency for Cu 2+ (99.1 %) and Pb 2+ (98.9 %). Notably, the layer-by-layer assembly strategy provides abundant groups for HMI binding, ensuring the high capture efficiency. The fabricated membrane demonstrated a low flux decline (9 %), along with a high flux recovery ratio (99.2 %). Moreover, it exhibited exceptional stability and reusability across a wide pH range (pH 5–9), meanwhile maintaining a capture efficiency of approximately 99 % under near-neutral condition after undergoing 5 cycle experiments for both Cu 2+ and Pb 2+ . Our work builds a straightforward approach for UF membrane fabricating with excellent HMI capture capacity, displaying the potential application in HMI waste water purification.