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 (∼10 nm 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.