Design of TiO₂ nanoparticle self-assembled aromatic polyamide thin-film-composite (TFC) membrane as an approach to solve biofouling problem

Microbial biofouling is one of the major obstacles for reaching the ultimate goal to realize high permeability over a prolonged period of reverse osmosis operation. In this study, the hybrid thin-film-composite (TFC) membrane consisted of self-assembly of TiO₂ nanoparticles with photocatalytic destructive capability on microorganisms was devised as a novel means to reduce membrane biofouling. Then, the anti-fouling and fouling mitigation on the actual commercialized TFC was verified. TiO₂ nanoparticles of a quantum size (∼10nm or less) in anatase crystal structure were prepared from the controlled hydrolysis of titanium tetraisopropoxide and characterized by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). Hybrid thin-film-composite (TFC) membrane was prepared by self-assembly of the TiO₂ nanoparticles through coordination and H-bonding interaction with the COOH functional group of aromatic polyamide thin-film layer, which was ascertained by X-ray photoelectron spectroscopy (XPS). The hybrid membrane was shown to possess the dramatic photobactericidal effect on Escherchia coli (E. coli) under UV light illumination. Finally, introduction of TiO₂ nanoparticles on the actual commercial TFC membrane and application of RO field test after exposure to microbial cells verified a substantial prevention against the microbial fouling by showing less loss of RO permeability, offering a strong potential for possible use as a new type of anti-biofouling TFC membrane.