Zwitterionic and hydrophilic polyelectrolyte/metal ion anti-fouling layers via covalent and coordination bonds for reverse osmosis membranes

Abstract

Reverse osmosis (RO) membrane technology, as an effective and eco-friendly method, has been widely used for seawater desalination and sewage treatment. However, RO membranes inevitably suffer serious organic and biological fouling during operation. Herein, we fabricated a hydrophilic anti-fouling layer on the RO membrane surface through the synergistic effect of covalent bonds and coordination bonds. Polyethyleneimine (PEI) and polyaspartic acid (PASP) are assembled onto the RO membrane surface successively. Fe(III) is utilized to induce further cross-linking for fabricating the PEI/PASP/Fe layer. The modified membranes exhibit superior hydrophilicity, whose water contact angle declines from 86.7° to 23.6°. In addition, the water flux of the PEI/PASP/Fe membrane increases by 45.8% with an excellent desalting property. Long-term, multi-cycle membrane fouling experiments demonstrate that the modified membrane manifests not only a lower flux loss rate (DR_t) but also a higher flux recovery rate (FRR). This means that the hydrophilic layer modified membranes show excellent separation performance even under severe environments, which is expected to boost the anti-fouling research in the membrane field.