Revisiting the role of H2O2 in periodate electro-activation system: The non-dependence in Bisphenol A (BPA) removal

Abstract

The existence of hydrogen peroxide (H2O2) within the electro-activation of periodate (PI) system is conventionally considered as conducive to the removal of pollutants. However, this study discovered an unusual phenomenon: the contaminants removal efficiency and the yield of strong oxidizing species such as hydroxyl radical (OH) and iodate radical (IO3) were improved when H2O2 in the solution was quenched. The study deeply explored the role of H2O2 in graphite felt-based electro-activated PI system (GF-PI), particularly in the mechanism of active species generation and contaminants removal. Bisphenol A (BPA), as the model contaminant, achieves a degradation efficiency of 82.1% and 83.9% within 40 min in w/wo H2O2 system, respectively. Meanwhile, multiple probing techniques clearly identify the variety of active species and generation pathway such as Electron paramagnetic resonance (EPR), LC-QTOF-MS, and quenching experiment. There exist two distinct pathways for PI activation, including direct cathodic electroreduction and indirect in-situ generated H2O2 catalysis. The GF-PI system incorporated both of two pathways, while the GF-PI-catalase system only had the direct activation pathway. Electrogenerated H2O2 serves as a precursor for the generation of superoxide radical anions (O2−) and singlet oxygen (1O2), yet it diminishes the efficiency of direct cathode activation due to the consumption of PI. Furthermore, the system demonstrated excellent stability, applicability, and cleanliness, effectively removing contaminations without the accumulation of iodine byproducts. The degradation intermediates products of BPA are monitored and the toxicities are evaluated. The study provides novel insights into the regulation of active species for contaminant elimination, holding significant implications for specialized sewage treatment.