Enhanced Transformation of Emerging Contaminants by Permanganate in the Presence of Redox Mediators

Abstract

In this study, a permanganate/redox mediator system for enhanced transformation of a series of emerging contaminants was evaluated. The presence of various redox mediators (i.e., 1-hydroxybenzotriazole, N-hydroxyphthalimide, violuric acid, syringaldehyde, vanillin, 4-hydroxycoumarin, and p-coumaric acid) accelerated the degradation of bisphenol A (BPA) by Mn­(VII). Since 1-hydroxybenzotriazole (HBT) exhibited the highest reactive ability, it was selected to further investigate the reaction mechanisms and quantify the effects of important reaction parameters on Mn­(VII)/redox-mediator reactions with BPA and bisphenol AF (BPAF). Interestingly, not only HBT accelerated the degradation of BPA, but also BPA enhanced the decay of HBT. Evidence for the in situ formation of HBT· radicals as the active oxidant responsible for accelerated BPA and BPAF degradation was obtained by radical scavenging experiments and 31P NMR spin trapping techniques. The routes for HBT· radical formation involving Mn­(VII) and the electron-transfer pathway from BPA/BPAF to HBT· radicals demonstrate that the Mn­(VII)/HBT system was driven by the electron-transfer mechanism. Compared to Mn­(VII) alone, the presence of HBT totally inhibited self-coupling of BPA and BPAF and promoted β-scission, hydroxylation, ring opening, and decarboxylation reactions. Moreover, Mn­(VII)/HBT is also effective in real waters with the order of river water > wastewater treatment plant (WWTP) effluent > deionized water.

Synergetic Hydroxyl Radical Oxidation with Atomic Hydrogen Reduction Lowers the Organochlorine Conversion Barrier and Potentiates Effective Contaminant Mineralization

“…Then, we systematically investigated the reasons for the efficient and complete removal of 4-CN and its intermediates under the synchronous redox conditions. We first sought to experimentally verify the beneficial effects of the synchronous redox synergy between H* and •OH on the 4-CN removal . A prerequisite for realizing this goal was to ensure that the reactions of either H* or •OH singly with 4-CN indeed occurred, and the synchronous redox synergy between H* and •OH showed a stronger tendency for the 4-CN removal than when H* or •OH reacted singly with 4-CN.…”

Insights into the Electron-Transfer Mechanism of Permanganate Activation by Graphite for Enhanced Oxidation of Sulfamethoxazole

“…For meeting the requirement of environmental remediation, advanced oxidation processes (AOPs) have attracted much attention because of their high efficiency and environmental friendliness . As one of the most promising oxidants, permanganate (KMnO 4 ) is extensively investigated toward water decontamination due to its stability, relatively low cost, and environmental friendliness. − However, the stability of KMnO 4 impedes its reactivity in some cases; thus, many efforts have been made to improve the reactivity of KMnO 4 by producing highly reactive intermediate Mn species such as Mn­(III), Mn­(V), and Mn­(VI), and other reactive oxygen species. − …”

The role of trace N-Oxyl compounds as redox mediator in enhancing antiviral ribavirin elimination in UV/Chlorine process

“…In recent years, trace organic redox mediators have been proposed. Nonetheless, there are only few researches focused on this field, which has limited their applications in the improvement of pollutants degradation by AOPs [14] , [15] , [16] , [17] .…”