Photocatalytic degradation of 17α-ethinylestradiol in mono- and binary systems of fulvic acid and Fe(III): Application of fluorescence excitation/emission matrixes

• EE2 photocatalytic removal is tracked by excitation/emission matrix (EEM).
• Removal of EE2 concentration correlates well with EEM changes.
• EEM changes are reflective of the formation of some fluorescent intermediates.
• EEM fluorescence is a powerful tool to monitor EE2 photocatalytic removal.
• The coexistence of FA and Fe(III) inhibits EE2 photocatalytic degradation.

Excitation/emission matrix (EEM) fluorescence spectroscopy was employed to characterize the photocatalytic degradation of 17α-ethinylestradiol (EE2) in mono- and binary systems of fulvic acid (FA) and ferric ions (Fe(III)). The decrease in fluorescence intensities of two characteristic peaks of EE2, whether at the peak maxima or regional integration, could be well described by the pseudo-first-order reaction kinetics. Photocatalysis was promoted by Fe(III) at low concentrations whereas inhibited by FA. Suppression in photocatalysis was observed in binary systems of FA and Fe(III), which can be attributed to photons competition of the FA–Fe(III) complex and aggregation of TiO2 particles. The kinetics rate constants determined by EEM, with relatively lower values, had significant linear correlations (p < 0.01) with those determined by EE2 concentration quantified using HPLC–MS. The relatively lower rate constants determined by EEM imply the formation of some fluorescent intermediates. This was verified by using the model compound phenol. The blue shifts of the fluorescent peaks of EE2 implied the decrease in aromatic moieties during photocatalysis. The results indicate that the fluorescence EEM can serve as a simple but utility tool for comparing the photocatalytic degradation kinetics and structural changes of EE2 under various conditions.

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