Fabrication of a novel acid-resistant nanofiltration membrane with dual-charged functional layer for metal ions recovery

Acid-resistant nanofiltration membranes contribute to an irreplaceable role in treating acidic solutions and recycling metal ions. Herein, an acid-resistant NF membrane with positively charged surface and negatively charged interlayer was exquisitely designed and fabricated via a two-step reaction process for metal ions recovery. Briefly, the negatively charged terephthalaldehyde/polyethyleneimine interlayer was obtained by the first-step reaction between terephthalaldehyde and polyethyleneimine, and the positively charged surface endowed acid resistance of polyethyleneimine/cyanuric chloride was acquired subsequently via the second-step reaction on the interlayer. The results clearly indicated the membrane possessed splendid performance because there was no obvious difference in separation performance before and after immersing in 0.1 mol·L-1 HNO3 solution for 60 days, and the rejections of MgCl2 and Na2SO4 can reach 96.34% and 60.15%, respectively. It exceeded 80% that the rejections of divalent ions in the real acidic leaching solutions of waste lithium battery. The fabricated membrane exhibited attractive separation performance and great feasibility for recovery of metal ions in acidic conditions.