Elucidating electro-oxidation kinetics of Fe(II) in the anode of air–cathode fuel cells from an Fe(II) speciation perspective

Understanding the Catalyst Regeneration Kinetics in the Chelated Iron Dehydrosulfurization Process: A Model in Terms of Fe(II) Speciation

“…The Fe­(EDTA) 2– is the most abundant species in the Fe­(II)-EDTA solution, whereas the Fe­(II)-NTA solution is dominated by the Fe­(NTA) − species. To facilitate calculation, the contributions of Fe 2+ , FeCl + , and FeSO 4 0 species to the overall Fe­(II) oxidation kinetics are ignored because of their inert activities in both the electrochemical and aerobic systems. ,,,, The Fe­(OH) 2 0 and Fe­(OH) + species are also neglected from eq owing to their low concentrations. As a result, eq is reduced to eqs and for the Fe­(II)-EDTA and Fe­(II)-NTA systems, respectively. …”

“…Figure shows the concentrations of kinetically active Fe­(II) species in a solution containing both the chelating agent and carbonate. In addition to the Fe­(OH)­(EDTA) 3– , Fe­(EDTA) 2– , Fe­(NTA) 2 4– , and Fe­(NTA) − species that are predicted to be kinetically active in this work, Fe­(OH) 2 0 , Fe­(OH) + , FeCO 3 0 , Fe­(CO 3 ) 2 2– , and Fe­(OH)­(CO 3 ) − species are also included in Figure because of their high reactivity in the oxidation. ,,, Fe­(EDTA) 2– and Fe­(NTA) − are the most abundant species dominating the EDTA- and NTA-chelated Fe­(II) systems, respectively. The Fe­(OH)­(EDTA) 3– , Fe­(NTA) 2 4– , and FeCO 3 0 species also exist at relatively higher concentrations in solution.…”

“…The oxidation kinetics of micromolar Fe­(II) at any given pH can be described by a general equation as where [Fe­(II)] T denotes total Fe­(II) concentration and k app is an apparent oxidation rate constant. At a fixed applied potential, the electrochemical oxidation of Fe­(II) on any certain electrode is assumed to follow a pseudo-first-order kinetics with respect to total Fe­(II) as where k ′ is a pseudo-first-order rate constant that is dependent upon the electrode property and solution composition. Similarly, in the O 2 -saturated solution where ambient O 2 concentration, [O 2 ], is in excess of [Fe­(II)] T , the aerobic oxidation kinetics of Fe­(II) is also expressed by eq where k ′ = k app [O 2 ] …”

“…Owing to the importance of iron cycling on natural aquatic systems, over the years, a large number of studies have been undertaken to elucidate the Fe­(II) oxidation kinetics in freshwater and saltwater environments. − These studies have shown convincingly that the chemical oxidation of Fe­(II) to Fe­(III) is a complex process involving a variety of Fe­(II) species with different kinetic activities. The Fe­(II) oxidation with O 2 in natural waters follows the Haber–Weiss mechanism, with reactions and being rate-limiting: …”

Emerging Strategies for Mitigating Acid Mine Drainage Formation and Environmental Impacts: A Comprehensive Review of Recent Advances

“…Efficiently removes organic compounds, destroys pathogens, and reduces contaminant levels. (Sun et al, 2015b;Sun et al, 2013;Tu et al, 2017;Zhai et al, 2013;Evangelou and Zhang, 1995) Electro-Fenton Generates oxidizing agents using electricity and Fe 2+ catalysts for contaminant breakdown.…”