In recent years, the perspectives of application of electrochemistry for environmental pollution abatement have been thoroughly investigated. The feasibility of electrochemical incineration of organic substrates in wastewater, in particular, has drawn much attention since pioneering papers by Stucki and Comninellis in early 90’s. In these works, the influence of the nature of the electrode material on the faradaic efficiency of the anodic mineralization of organics has been considered in detail, showing that optimal conditions for the process in question are met at high-oxygen-overpotential anodes, like SnO2 and PbO2. Basing on these evidences, Comninellis has proposed a general model, which satisfactorily accounts for the different results described in the literature. More recent results, obtained at conductive diamond electrodes, characterized by very high oxygen overpotential, also fit in the model predictions quite well. Model organic substrates, like glucose, aldonic and aldaric acids, show a complex reactivity toward the anodic mineralization. In fact, in these cases, besides the central role of adsorbed hydroxyl radicals, also the mode of adsorption of the organic species has to be taken into account. Simpler molecules, like oxalic acid, also support the view that co-electrosorption of hydroxyl radicals and organic species decides of the rate of the anodic mineralization, volcano-plot-approaches of the type applied long since for ethylene electrochemical oxidation being possibly a good interpretative tool. These considerations afford further evidence to the importance of the nature of the electrode material in electrochemical incineration. Taking into consideration the role of mediators, like Cl-, of particular interest for its common presence in many different types of wastewater, interpretations may be attempted, bringing again the role of the electrode material in a prominent position. Chloride-mediated incineration can be properly accounted for by assumptions on co-adsorbed hydroxy- and chloro-radicals at the electrode surface and on the effect of this on the rate of oxygen evolution reaction.
Electrochemical incineration of organics. Combined role of mediation and electrode material
MARTINEZ, Carlos Alberto;FERRO, Sergio;DE BATTISTI, Achille
2004
Abstract
In recent years, the perspectives of application of electrochemistry for environmental pollution abatement have been thoroughly investigated. The feasibility of electrochemical incineration of organic substrates in wastewater, in particular, has drawn much attention since pioneering papers by Stucki and Comninellis in early 90’s. In these works, the influence of the nature of the electrode material on the faradaic efficiency of the anodic mineralization of organics has been considered in detail, showing that optimal conditions for the process in question are met at high-oxygen-overpotential anodes, like SnO2 and PbO2. Basing on these evidences, Comninellis has proposed a general model, which satisfactorily accounts for the different results described in the literature. More recent results, obtained at conductive diamond electrodes, characterized by very high oxygen overpotential, also fit in the model predictions quite well. Model organic substrates, like glucose, aldonic and aldaric acids, show a complex reactivity toward the anodic mineralization. In fact, in these cases, besides the central role of adsorbed hydroxyl radicals, also the mode of adsorption of the organic species has to be taken into account. Simpler molecules, like oxalic acid, also support the view that co-electrosorption of hydroxyl radicals and organic species decides of the rate of the anodic mineralization, volcano-plot-approaches of the type applied long since for ethylene electrochemical oxidation being possibly a good interpretative tool. These considerations afford further evidence to the importance of the nature of the electrode material in electrochemical incineration. Taking into consideration the role of mediators, like Cl-, of particular interest for its common presence in many different types of wastewater, interpretations may be attempted, bringing again the role of the electrode material in a prominent position. Chloride-mediated incineration can be properly accounted for by assumptions on co-adsorbed hydroxy- and chloro-radicals at the electrode surface and on the effect of this on the rate of oxygen evolution reaction.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
