Removal of 6PPD-quinone by Fe(II)-GLDA complex-activated periodate under neutral conditions

The effect of N , N -bis(carboxymethyl)glutamic acid (GLDA) on the removal of organic pollutants by Fe(II)-mediated periodate (PI) advanced oxidation process at neutral pH was investigated, in which N-(1,3-dimethylbutyl)- N ′-phenyl- p -phenylenediamine quinone (6PPD-Q) was used as the model pollutant. The results showed that the Fe(II)-GLDA complex formed by mixing GLDA with Fe(II) in a 1:1 ratio reacted with PI can degrade 6PPD-Q effectively. The presence of GLDA alters the redox potential of Fe(II)/Fe(III), which allows for a better utilization of Fe(II) under the synergistic effect of ultraviolet (UV) irradiation. Based on quenching experiments, sulfoxide probe transformation and electron spin resonance (ESR) signals, the reactive species that play a major role in this process are Fe IV O and IO 3 . The degradation products of 6PPD-Q were detected by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS) and two possible degradation pathways were proposed based on density functional theory (DFT) calculations. The toxicity of 6PPD-Q was found to be effectively reduced after degradation by Ecological Structure Activity Relationships (ECOSAR) software analysis and zebrafish experiments. This study provides some fundamental insights for the removal of organic pollutants by GLDA-enhanced Fe(II)/PI system under neutral conditions.