Transient Chemiluminescence Assay for Real-Time Monitoring of the Processes of SO 3 2- -Based Advanced Oxidation Reactions.

The hydroxyl radical (·OH) is a strong oxidizing agent in situ generated in advanced oxidation processes (AOPs) and crucial for assessing the performances of AOPs toward organic contaminants' degradation. Herein, we developed a specific luminescent probe, APDI ( N ' N '-di(propylethylenediamine)-perylene-3,4,9,10-tetracarboxylic diimide), to selectively detect ·OH among diverse reactive oxygen species and other radicals. Based on the transient chemiluminescence (TCL) spectra, the in situ concentration profile of ·OH within 0.01 s interval time in classical Fenton reactions and four kinds of SO 3 2- -based AOPs was obtained, which provides insights into the high dynamic processes of the whole ·OH generation and consumption processes. Besides, compared with acidic conditions, reduced degradation efficiencies in Fe 2+ -SO 3 2- and Fe 2+ -SO 3 2- -H 2 O 2 systems were found under neutral conditions. The complete depletion of active free radicals due to SO 2 - ̇ radicals generated from Fe 2+ and SO 3 2- should account most for decreased degradation efficiencies evidenced by a new SO 2 * TCL signal discovered in the TCL spectra. In addition, similar phenomena have also been found in other M ( n -1)+ -SO 3 2- -related AOPs. As SO 3 2- and HSO 3 - often exist naturally in wastewater, more efforts are needed to improve the performance of Fe 2+ -H 2 O 2 systems. This discovery has important significance for organic contaminant degradation in a natural environment.