Polyethyleneimine/4,4′-Bis(chloromethyl)-1,1′-biphenyl nanofiltration membrane for metal ions removal in acid wastewater

The metal ions separation in acid wastewater is of great significance. Nanofiltration (NF) is an effective method to solve this problem. In this work, an acid-resistant PEI/BCMP NF membrane was obtained by chemically crosslinking polyethyleneimine (PEI) and 4,4′-Bis(chloromethyl)-1,1′-biphenyl (BCMP) on the polyethersulfone ultrafiltration (PESU) membrane. Concentration and heat treatment conditions for the membrane preparation were analyzed in detail. The PEI/BCMP membrane formed with 0.6% (m/v) PEI and 0.02% (m/v) BCMP at 80 °C for 10 min exhibited excellent performance. The membrane prepared in the state could be applied in acidic metal salt solutions. The Donnan effect caused the high selectivity for metal cations. At the same time, the loose structure improved the permeability. In the acidic (HCl) solution, the PEI/BCMP membrane showed a strong selectivity for metal ions (FeCl 3 99.5%, CuCl 2 92.2%, ZnCl 2 91.3%). After a long time operation, the membrane performance is still stable.