Enhanced antibiofouling of RO membranes via polydopamine coating and polyzwitterion immobilization

• Polydopamine (PDA) was coated on RO membrane as a precursor layer.
• Polyzwitterion was covalently immobilized on PDA coating layer.
• Antibiofouling properties of modified membranes were successfully improved.
• Stability of immobilized polyzwitterion was improved by PDA precursor layer.

It has been reported that polyzwitterions (PZs) can significantly improve the antibiofouling properties of membrane surfaces. In addition, it is known that polydopamine (PDA) can deposit non-selectively from solution onto virtually any solid surface and creates a versatile surface for further modification through its reactive groups. In this paper, we attempted to use a PDA coating as a precursor layer to enhance the durability and antibiofouling potential of a PZ-immobilized membrane. The deposition of PDA and PZ was confirmed by X-ray photoelectron spectroscopy. The hydrophilicity was not markedly increased by surface modification. Moreover, the membrane surface charge density was changed from negative to neutral by PZ immobilization. Nevertheless, an improvement in antibiofouling properties was confirmed by cross-flow filtration of a bacterial (Pseudomonas putida) suspension. The high antiadhesion properties of membranes modified with a PDA coating and/or PZ immobilization was confirmed by scanning electron microscope surface images after 1200 min filtration of the bacterial suspension. Moreover, the PDA precursor layer was confirmed to increase the stability of a PZ layer immobilized on the membrane surface by bacterial suspension filtration experiments after one month of immersion in 2 M NaCl aqueous solution.