Degrading two endocrine-disrupting chemicals from water by UV irradiation with the presence of nanophotocatalysts

Abstract

The photocatalytic degradation of two selected endocrine-disrupting chemicals (EDCs) namely phenol and resorcinol was investigated in TiO₂ and ZnO aqueous suspensions under UV irradiation. These catalysts were investigated for crystallinity, surface area, and optical properties. The effects of various operating parameters including the photocatalyst dosage, solution pH, initial substrate concentration, and the presence of second substrate on photocatalytic degradation were studied. Under optimized conditions, ZnO showed greater degradation and mineralization activities as it absorbed more light quanta than TiO₂. Several degradation intermediates were detected using HPLC, which allowed the proposal of tentative pathways for the photocatalytic degradation of phenol and resorcinol. By investigating the effect of various radical scavengers, it showed that the photocatalytic degradation of phenol and resorcinol took place mainly via the hydroxyl radicals. The ZnO photocatalyst was also reused for several times and without considerable loss of activity. Compared to the single solutions, the degradation efficiencies of binary solutions decreased. The difference between the observed rate constants of phenol and resorcinol in binary solutions became lesser compared to the cases in single solutions. Furthermore, the photocatalytic degradation of either single or binary substrate in aqueous solutions satisfactorily obeyed the pseudo-first-order kinetics.

Keywords:

• Photocatalysis
• Phenol
• Resorcinol
• Endocrine-disrupting chemicals
• Degradation intermediates
• Binary solutions

Acknowledgments

This study was supported under Research Universiti (RU) Grants (Nos. 854001 and 814004) from Universiti Sains Malaysia. The authors gratefully acknowledged the financial support from the Malaysia Government through the MyPhD scheme.