Enhancing Fenton-like process at neutral pH by Fe(III)-GLDA complexation for the oxidation removal of organic pollutants

N,N-bis(carboxymethyl)glutamic acid (GLDA) was utilized in this study to significantly enhance the Fe(III) mediated Fenton-like oxidation removal of organic pollutants at neutral pH, in which ciprofloxacin (CIP) was used as the model pollutant. The CIP degradation rate in the GLDA/Fe(III)/H2O2 system reached 96.5% within 180 min and was nearly 14 times higher than that in the Fe(III)/H2O2 system. This enhancement was contributed to the acceleration of the cycle of Fe(III)/Fe(II) caused by GLDA, which was verified by UV-vis spectroscopy, cyclic voltammetry, and radical quenching experiments. The results proved that the GLDA could complex with Fe (III) and greatly modify the redox potential of Fe(III)/Fe(II). Moreover, radical quenching experiments confirmed that center dot OH and O-2(center dot-) were the mainly species for CIP degradation, and O-2(center dot-) was responsible for 81.9% center dot OH generation. In addition, H2O2 utilization kinetic modeling was also investigated. The optimum parameters of the 100 mu M Fe(III)-GLDA complex and 15 mM H2O2 were attained by lot-size optimization experiments. Two possible CIP degradation pathways were proposed on the basis of the intermediates identified by MS/MS. The GLDA/Fe(III)/H2O2 system performed better than common chelating agents at the same condition, manifesting good potential for environmental concerns.

Automated summary

Utilizing N,N-bis(carboxymethyl)glutamic acid (GLDA) in Fe(III) mediated Fenton-like oxidation significantly enhances the removal of organic pollutants at neutral pH. The acceleration of the Fe(III)/Fe(II) cycle caused by GLDA contributes to the increased degradation rate of pollutants, especially ciprofloxacin (CIP), in the GLDA/Fe(III)/H2O2 system. The complexation of GLDA with Fe(III) modifies the redox potential and enhances the generation of hydroxyl radicals, leading to efficient pollutant degradation.