Enhanced Direct Electron Transfer Mediated Contaminant Degradation by Fe(IV) Using a Carbon Black-Supported Fe(III)-TAML Suspension Electrode System

Abstract

Iron complexes of tetra-amido macrocyclic ligands (Fe-TAML) are recognized to be effective catalysts for the degradation of a wide range of organic contaminants in homogeneous conditions with the high valent Fe(IV) and Fe(V) species generated on activation of the Fe-TAML complex by hydrogen peroxide (H2O2) recognized to be powerful oxidants. Electrochemical activation of Fe-TAML would appear an attractive alternative to H2O2 activation, especially if the Fe-TAML complex could be attached to the anode, as this would enable formation of high valent iron species at the anode and, importantly, retention of the valuable Fe-TAML complex within the reaction system. In this work, we affix Fe-TAML to the surface of carbon black particles and apply this “suspension anode” process to oxidize selected target compounds via generation of high valent iron species. We show that the overpotential for Fe(IV) formation is 0.17 V lower than the potential required to generate Fe(IV) electrochemically in homogeneous solution and also show that the stability of the Fe(IV) species is enhanced considerably compared to the homogeneous Fe-TAML case. Application of the carbon black-supported Fe-TAML suspension anode reactor to degradation of oxalate and hydroquinone with an initial pH value of 3 resulted in oxidation rate constants that were up to three times higher than could be achieved by anodic oxidation in the absence of Fe-TAML and at energy consumptions per order of removal substantially lower than could be achieved by alternate technologies.

Critical Role of Mineral Fe(IV) Formation in Low Hydroxyl Radical Yields during Fe(II)-Bearing Clay Mineral Oxygenation

“…This result suggests that structural Fe­(II), rather than aqueous Fe 2+ dominated the formation of PMSO 2 [i.e., Fe­(IV)]. Many previous studies have demonstrated the formation of aqueous Fe­(IV) during the oxidation of Fe 2+ in advanced oxidation processes. − Our results extended the generation of Fe­(IV) from homogeneous Fe 2+ systems to structural Fe­(II) associated with clay minerals.…”

Enhanced sodium ion storage in MnO2 through asymmetric orbital hybridization induced by spin-paired ion doping

“…The electronic structures of transition metals (TMs) are intimately connected to the conguration of atomic orbital hybridization. [14][15][16] Novel methodologies to regulate the d orbitals of TMs have recently been exploited. [17][18][19] For example, Liu et al designed asymmetrically coordinated Fe-N 3 C 2 to promote Fe (3d)-S (2p) orbital hybridization, engendering a robust chemical affinity for lithium polysuldes.…”

CuO/g-C3N4 Nanocomposites for Enhanced Glyphosate Degradation: The Vital Role of High-Valent Copper

“…A conventional Fenton reaction is mainly based on the generation of free radicals for the degradation of organic pollutants. , However, treatment of practical organic wastewater with free radicals could face a range of challenges, such as natural matrix in water, inorganic ions and even the pH of solution, , which would greatly inhibit the degradation efficiency of organic pollutants. Recently, high-valent metal species, such as high-valent iron (Fe(IV) and Fe(V)), − cobalt (Co(IV)), and copper (Cu(III)) , generated in peroxide activated by metal catalysts have been proved to show excellent oxidation ability toward organic pollutants compared to radicals. At the same time, they also had the advantage of higher resistance to environmental interference and even exhibited excellent removal properties on trace pollutants. − …”