An Fe(III)/H₂O₂ Fenton-like process enhanced by Rifampicin: The role of hydroquinone moiety

The co-catalytic effect of hydroquinone/quinone electron shuttle has received great attention in the area of Fenton-like reaction. However, the crucial roles of phenolic or hydroquinone moieties in the chemical structures of organic pollutants have always been overlooked. In this study, we discovered that the introduction of rifampicin (RIF), a representative of rifamycin antibiotics, could trigger complete degradation of atrazine (ATZ) in the Fe(III)/H₂O₂ system. By exploring the influences of initial Fe(III), H₂O₂, RIF concentrations and pH values on ATZ degradation efficiency, key components affecting metal ion valence transitions in the system were identified. Quenching experiments, probe tests and EPR analysis verified that •OH served as the primary active species, while HO₂•/O₂^•- was also generated. Through monitoring Fe(II) concentration variations and employing mass spectrometric analyses, the oxidation pathway of RIF was elucidated: When mixed with Fe(III), the naphthohydroquinone moiety of RIF immediately acted as a direct electron donor to reduce Fe(III) to Fe(II), while itself being oxidized to RIF-Q. Upon H₂O₂ addition, it rapidly triggered the classical Fenton reaction with Fe(II) to generate •OH, enabling ATZ degradation. Simultaneously, RIF-Q underwent further oxidative breakdown, with some degradation products retaining the capacity to continuously donate electrons to Fe(III), thereby promoting its reduction. This study provides new insights for the co-catalytic effect of pollutant-derived electron shuttles on the transition of metal ion valences.