Photodegradation mechanism for bisphenol A at the TiO2/H2O interfaces

Bisphenol A (BPA) can be decomposed photocatalytically under UV-illumination in aqueous TiO2 dispersion. The two methyl groups in BPA were initially attacked with .OH and/or .OOH radicals having strong oxidizing power, followed by the cleavage of the two phenyl moieties. Finally, the photomineralization to CO2 gas occurred via oxidative processes involving carboxylic acids and aldehydes. The decomposition of structurally similar substances of 4,4'-ethylidenebisphenol (EBP) and 4,4'-methylenebisphenol (MBP) was compared. The decomposition of BPA gave more kinds of intermediates such as 4-isopropylphenol, 4-ethylphenol, etc. On the other hand, that of EBP gave mainly 4-isopropylphenol and that of MBP gave a predominant product of 4-hydroxybenzaldehyde. These photooxidative pathways were proposed on the base of the evidence of oxidative intermediate formation.