O objetivo deste trabalho é discutir a oxidação eletroquímica do ácido oxálico (AO), analisando a influência do NaCl e NaBr. Experimentos foram realizados em eletrodos de diamante dopados com boro (DDB), em meio alcalino. Eletrodos DDB têm uma baixa adsortividade superficial, portanto sua grande estabilidade frente à oxidação permite que a reação ocorra com reagentes e intermediários não adsorvidos. O processo é significativamente acelerado pela presença de sal de halogênio na solução; curiosamente, o processo mediado não depende da densidade de corrente aplicada. Com base nos resultados, o brometo foi selecionado como um mediador apropriado durante a oxidação de AO em DDB. Br -age primeiramente no volume da solução, com a formação de oxidantes fortes, enquanto a ação do Cl -mostrou melhoras mais baixas na oxidação do AO em BDD, com relação aos resultados relatados usando eletrodo de Pt. Finalmente, os parâmetros de eficiência de remoção e consumo de energia para a incineração eletroquímica de AO foram calculados.Aim of this work is to discuss the electrochemical oxidation of oxalic acid (OA), analyzing the influence of NaCl and NaBr. Experiments were carried out at boron-doped diamond (BDD) electrodes, in alkaline media. BDD electrodes have a poor superficial adsorptivity so their great stability toward oxidation allows the reaction to take place with reactants and intermediates in a non-adsorbed state. The process is significantly accelerated by the presence of a halogen salt in solution; interestingly, the mediated process does not depend on applied current density. Based on the results, bromide was selected as a suitable mediator during OA oxidation at BDD. Br -primarily acts in the volume of the solution, with the formation of strong oxidants; while Cl -action has shown lower improvements in the OA oxidation rate at BDD respect to the results reported using Pt electrode. Finally, the parameters of removal efficiency and energy consumption for the electrochemical incineration of OA were calculated.Keywords: indirect oxidation, mediators, oxalic acid, halides, boron doped diamond IntroductionElectrochemical treatment is one of the methods used for the removal of organic and inorganic impurities from water and waste water. Consequently, several research groups are attempting to use electrochemical methods as an effective method for detoxification of wastewaters containing biorefractory pollutants. [1][2][3][4][5][6][7][8] The literature has shown that, the electrochemical oxidation represents an alternative in wastewater treatment, [6][7][8][9] and this process can be subdivided in two main categories: "Direct" and "Indirect" as schematized in Table 1. According to information in Table 1, while the electron transfer takes place between electrodes and decomposable species in direct electrochemical oxidation, indirect oxidation mainly uses electrochemically oxidized species as mediators for the destruction of organic compounds. Reactive and high-valent metal ions which are electrochemically generated from stable...

In this paper are presented data on the preparation and characterization of different oxide electrodes. RuO2–TiO2, IrO2–TiO2, and SnO2–Sb2O5 mixed-oxide films have been taken as model systems. For the first, the traditional preparation method based on the pyrolysis of precursor salt deposits was adopted. For the SnO2-based films, the spray pyrolysis preparation has been used. The characterization of RuO2–TiO2 films confirms the existence of a solid solution between the two component oxides over a wide composition range. Rutherford backscattering spectrometry confirms the occurrence of segregation of titanium oxide species in the outermost part of the films. Nuclear reaction analysis indicates that large amounts of carbon and hydrogen impurities are trapped in the oxide films. SnO2-based films were found to be less porous and chemically more simple. The differences between the two systems have been discussed in terms of the preparation method and the differences in chemical properties of the precursors. Keywords: oxide film electrodes, mixed-oxide films, Rutherford backscattering spectrometry, nuclear reaction analysis.

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IrO 2 and Ta 2 O 5 mixed oxide coatings were deposited on Ti supports in order to fabricate dimensionally stable electrodes used in chloro-alkali technology. Secondary ion mass spectrometry (SIMS) and electrochemical experiments were carried out in order to characterize these materials. Electrochemical tests found the highest electrocatalytic activity for 50% IrO 2 -50% Ta 2 O 5 electrodes. SIMS analyses are in harmony with these results, and it is shown that IrO 2 is more diluted on the surface for noble metal oxide concentrations higher than 50%. Finally, it was observed by SIMS that support material migration was favoured at the highest concentrations of Ta 2 O 5 stabilizer.

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