Mechanism and experimental study on the photocatalytic performance of Ag/AgCl @ chiral TiO2 nanofibers photocatalyst: the impact of wastewater components

Abstract

The effect of the water matrix components of a secondary effluent of a urban wastewater treatment plant on the photocatalytic activity of Ag/AgCl @ chiral TiO2 nanofibers and the undergoing reaction mechanisms were investigated. These effects were evaluated through the water components-induced changes on the net rate of hydroxyl radical (˙OH) generation and modeled using a relative rate technique. Dissolved organic matter DOM (k=-2.8×10(8) M(-1) s(-1)) scavenged reactive oxygen species, Cl(-) (k=-5.3×10(8) M(-1) s(-1)) accelerated the transformation from Ag to AgCl (which is not photocatalytically active under visible-light irradiation), while Ca(2+) at concentrations higher than 50 mM (k=-1.3×10(9) M(-1) s(-1)) induced aggregation of Ag/AgCl and thus all of them revealed inhibitory effects. In contrast, NO3(-) (k=6.9×10(8) M(-1) s(-1)) and CO3(2-) (k=3.7×10(8) M(-1) s(-1)) improved the photocatalytic activity of Ag/AgCl slightly by improving the rate of HO˙ generation. Other ubiquitous secondary effluent components including SO4(2-) (k=3.9×10(5) M(-1) s(-1)), NH3(+) (k=3.5×10(5) M(-1) s(-1)) and Na(+) (k=2.6×10(4) M(-1) s(-1)) had negligible effects. 90% of 17-α-ethynylestradiol (EE2) spiked in the secondary effluent was removed within 12 min, while the structure and size of Ag/AgCl @ chiral TiO2 nanofibers remained stable. This work may be helpful not only to uncover the photocatalytic mechanism of Ag/AgCl based photocatalyst but also to elucidate the transformation and transportation of Ag and AgCl in natural water.

Keywords: Ag; AgCl; Photocatalytic performance; Transformation; Wastewater components.