Chemiluminescence as a New Indicator for Monitoring Hydroxylated Intermediates in Persulfate-Based Advanced Oxidation Processes

The formation of hydroxylated intermediates is the first step in the persulfate-based advanced oxidation processes (AOPs) and depends directly on the oxidation degree of recalcitrant pollutants. Therefore, the monitoring of hydroxylated intermediates plays a vital role in persulfate-based AOPs for evaluating the oxidation degree and understanding the degradation mechanism. In this work, based on the attractive amplification of luminol chemiluminescence (CL) signals by hydroxylated intermediates, we developed a rapid, sensitive, and simple CL-based method to monitor hydroxylated intermediate (i.e., 3,5-diethyl-1,4-benzenediol) generated in persulfate-based AOPs of 1,2-divinylbenzene (DVB). The possible mechanism of the proposed CL system was that hydroxylated intermediates could be oxidized by persulfate in alkaline solution to form superoxide anion radicals and thus lead to an increase in the luminol CL. Finally, the proposed CL system was successfully applied in monitoring hydroxylated intermediates generated during persulfate-based AOPs under different degradation conditions, whose validity and reliability were verified by liquid chromatography-mass spectrometry (LC-MS) and Fourier-transform infrared spectroscopy (FT-IR). The generality of the proposed CL system was verified by monitoring hydroxylated intermediates generated in persulfate-based AOPs of methylbenzene and benzoic acid. These results suggested that this present CL system provided a promising indicator for monitoring hydroxylated intermediates in persulfate-based AOPs.