Naproxen as a Turn-On Chemiluminescent Probe for Real-Time Quantification of Sulfate Radicals

Current techniques for identifying and quantifying sulfate radicals (SO₄^·-) in SO₄^·--based advanced oxidation processes (SR-AOPs) are unsatisfactory due to their low selectivity, poor reliability, and limited feasibility for real-time quantification. In this study, naproxen (NAP) was employed as a turn-on luminescent probe for real-time quantification of SO₄^·- in SR-AOPs. The chemiluminescence(CL) yield (Φ_CL) of the reaction of NAP with SO₄^·- was first determined to be 1.49 × 10^-5 E mol^-1 with the bisulfite activation by cerium(IV) [Ce(IV)/BS] process. Then, the maximum peak concentrations of SO₄^·- in the Ce(IV)/BS-NAP process was quantified to be ∼10^-11 M based on the derived equation. Since Φ_CL of the reaction of NAP with SO₄^·- was much greater than that with other reactive oxidizing species (ROS), the developed CL method worked well in selective quantification of SO₄^·- in various SR-AOPs (e.g., the activation of peroxymonosulfate and persulfate by iron processes). Finally, the electron transfer from NAP to SO₄^·- was proposed to be the critical step for CL production. This work provides a novel CL method for real-time quantification of SO₄^·-, which facilitates the development of SR-AOPs and their application in water and wastewater treatment.