Comparative study of naphthalene removal in different radicals-dominated systems: Kinetics, degradation intermediates, and pathways

Abstract

The investigation on naphthalene (NAP) removal has been reported by increasing literatures due to its frequent detection in contaminated sites. However, the degradation intermediates of NAP in different radicals-dominated systems, as well as the estimation of their toxicities, have not been systematically illuminated. In this work, the degradation intermediates and pathways of NAP were thoroughly compared in hydroxyl radical (HO•) and sulfate radical (SO4−•) driven systems, and the radical addition was the dominant mechanism in both two systems. The toxicological assessment of 27 NAP degradation intermediates were performed, suggesting that the acute toxicity of intermediates produced by SO4−• addition could be weakened. Moreover, a kinetic model was established to simulate the kinetics of NAP degradation at various conditions, and the simulated results were in keeping with the experimental values. The effects of chemical concentration (NAP, oxidant, HCO3−, and Cl−) and solution pH on NAP removal were elucidated. The steady-state concentrations of radicals and their contribution to NAP removal were determined by the model. Finally, the performance of significant mineralization of NAP (96.9%) in SO4−•-driven system confirmed the superiority of SO4−•-based advanced oxidation technique in the remediation of NAP-contaminated site.