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 HNO 3 solution for 60 days, and the rejections of MgCl 2 and Na 2 SO 4 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.