Diurnal-independent, visible-light-storing of Ag2O@SrAl2O4:Eu2+,Dy3+ for the round-the-clock decomposition of ciprofloxacin

Abstract

A round-the-clock photocatalyst that can efficiently separate charge carriers will break through the practical application of photocatalytic-based advanced oxidation processes (PC-AOPs) in wastewater treatment. In this work, an energy-storable p-n heterojunction Ag2O@SrAl2O4:Eu2+,Dy3+ (Ag2O@SAED) was successfully prepared to achieve round-the-clock photocatalytic degradation of ciprofloxacin (CIP). Ag2O@SAED can efficiently degrade ∼ 80 % of CIP (with ∼ 56 % mineralization) under low power consumption of 12 W LED visible light source radiation for 2 h. In addition, surprisingly, Ag2O@SAED also shows certain energy storage properties, so that it can effectively reduce the energy consumption of the treatment process compared with conventional photocatalytic processes. Non-radical singlet oxygen (1O2) is the main reactive species, which is produced mainly from intermediate superoxide radicals (·O2−). Moreover, the site of CIP attacked by 1O2 was tentatively confirmed by Fukui index based on density functional theory (DFT) calculations. The activities of round-the-clock degradation of CIP in different water matrices were examined. The degradation efficiency in tap water, Yangtze River and wastewater plant effluent were 61.88 %, 57.61 % and 55.87 %, respectively. The synergistic effect of p-n heterojunctions is effective in degrading CIP during daytime, and the light released from SAED activates the activity of Ag2O to degrade CIP at night. This study contributes to further understanding the principles and mechanisms of round-the-clock photocatalysts for degradation of organic pollutants and provides directions for the practical application of photocatalytic technology.