Giacomo Cerisola

Electrochemical oxidation of phenol at boron-doped diamond electrode

The electrochemical behaviour of a synthetic boron-doped diamond thin film electrode (BDD) has been studied in acid media containing phenol using cyclic voltammetry and bulk electrolysis. The results have shown that in the potential region of water stability direct electron transfers can occur on BDD surface resulting in electrode fouling due to the formation of a polymeric film on its surface. During electrolysis in the potential region of oxygen evolution, complex oxidation reactions can take place due to electrogenerated hydroxyl radicals. Electrode fouling is inhibited under these conditions. Depending on the experimental conditions, the electrogenerated hydroxyl radicals can lead to the combustion of phenol or to the selective oxidation of phenol to benzoquinone. The experimental results have also been compared to a theoretical model that permits the prediction of the evolution with time of phenol concentration, during its combustion, or during its selective oxidation to benzoquinone.

Anodic oxidation of 2-naphthol at boron-doped diamond electrodes

Abstract The anodic oxidation of 2-naphthol in acid media was investigated at a synthetic boron-doped diamond thin film electrode (BDD) using cyclic voltammetry and bulk electrolysis. The results have shown that in the potential region, where the supporting electrolyte is stable, reactions involving simple electron transfer, such as oxidation of 2-naphthol to naphthoxy radical and 1,4-naphthoquinone occur. Polymeric materials, which lead to electrode fouling, are also formed in this potential region. Electrolysis at high positive potentials in the region of electrolyte decomposition causes complex oxidation reactions by electrogenerated hydroxyl radicals leading to the complete incineration of 2-naphthol. Electrode fouling is inhibited under these conditions. The experimental results have been also compared with a theoretical model. This model is based on the assumption that the rate of the anodic oxidation of 2-naphthol is a fast reaction and it is under diffusion control.

Oxidation of 4-Chlorophenol at Boron-Doped Diamond Electrode for Wastewater Treatment

The electrochem. behavior of synthetic B-doped diamond thin-film electrode (BDD) was studied in acid media contg. 4-chlorophenol (4-CP) by cyclic voltammetry, chronoamperometry, and bulk electrolysis. The results showed that in the potential region of supporting electrolyte stability occur reactions involving the oxidn. of 4-CP to phenoxy radical and 1,4-benzoquinone. Polymeric materials, which result in electrode fouling, are also formed in this potential region. Electrolysis at high anodic potentials, in the region of electrolyte decompn., complex oxidn. reactions can take place involving electro-generated hydroxyl radicals, leading to the complete incineration of 4-chlorophenol. Electrode fouling is inhibited under these conditions. The exptl. results were compared with a theor. model. This model is based on the assumption that the rate of the anodic oxidn. of 4-CP is a fast reaction. HPLC analyses revealed that the main intermediate products of 4-CP oxidn. were 1,4-benzoquinone, maleic acid, formic acid, and oxalic acid. [on SciFinder (R)]

Electro-Fenton degradation of synthetic dyes.

The electrochemical removal of a synthetic solution containing 120mgL(-1) of alizarin red has been studied by electro-Fenton process using a gas-diffusion cathode to produce in situ hydrogen peroxide by oxygen reduction. The effect of operating conditions such as Fe(2+) concentration, applied current, solution pH and temperature on the efficacy of the process was investigated. It is shown that alizarin red and its products may be effectively degraded by the OH radicals produced by the reaction between the Fe(2+) ions and the electrogenerated H(2)O(2). After 4h of electrolysis COD removal was only 45% when no ferrous ions were added to the solutions, while the presence of ferrous ion greatly improved COD removal up to more than 90%. In particular 1.0mM was the optimal concentration of ferrous ions and the single step or the stepwise addition of Fe(2+) ions enables the same COD removal. The oxidation rate increased with increasing of current density and temperature and with decreasing of pH. The UV-vis analysis indicated that the discoloration of the solution occurs simultaneous with the destruction of aromatic rings and alizarin red is oxidised firstly to colourless intermediates (mainly phthalic acid, small carbonyl species) and then to carbon dioxide.

Electrochemical treatment of wastewater containing polyaromatic organic pollutants

Disposal of industrial wastewater containing naphthalene- and anthraquinone-sulphonic acids by electrochemical methods has been studied in this paper. It was found that only a small fraction of the organics was oxidised by direct electrolyses, while complete mineralisation of the organics was obtained with the indirect process, electrogenerating hypochlorite from chloride oxidation. The effects of operating factors, such as anode materials and chloride concentration, were also investigated. The experimental data suggested that the Ti/Pt anodes had the highest electrocatalytic activity and increasing the chloride concentration in the electrolyte resulted in an increasing of COD and colour removal.

Removal of organic pollutants from industrial wastewater by electrogenerated Fenton's reagent.

This study was performed to investigate the treatment of an industrial wastewater mainly containing naphthalene- and anthraquinone-sulphonic acids, by electrogenerated Fentons reagent. The hydrogen peroxide was produced in situ by electrochemical reduction of oxygen on graphite-felt cathodes and the Fe2+ ions were also regenerated by cathodic reduction of Fe3+. The influence of cathode potential, Fe2+ concentration and electrode surface pre-treatment on chemical oxygen demand (COD) removal and colour fading were studied. Results indicated that the higher COD removal was obtained in the presence of 3 mM of ferrous ions working at a constant potential of -1 V vs. SCE. Moreover, it was shown that both chemical and electrochemical pre-treatments of the cathode surface resulted in a decrease of COD depletion.

Electrochemical treatment of wastewaters containing organic pollutants on boron-doped diamond electrodes: Prediction of specific energy consumption and required electrode area

A theoretical analysis is presented for the prediction of the specific energy consumption and the required electrode surface for the electrochemical combustion of organic compounds on synthetic boron-doped diamond (BDD) thin film electrodes. The model is formulated for a perfect mixed electrochemical reactor operated as a batch recirculation system under galvanostatic conditions. The anodic oxidation of organics is assumed to be under diffusion control. An experimental validation with the anodic oxidation of phenol and under different experimental conditions is also provided.

Influence of anode material on the electrochemical oxidation of 2-naphthol: Part 1. Cyclic voltammetry and potential step experiments

Abstract The anodic oxidation of 2-naphthol has been studied by cyclic voltammetry and chronoamperometry, using a range of electrode materials such as Ti–Ru–Sn ternary oxide, lead dioxide and boron-doped diamond (BDD) anodes. The results show that polymeric films, which cause electrode fouling, are formed during oxidation in the potential region of supporting electrolyte stability. IR spectroscopy verified the formation of this organic film. While the Ti–Ru–Sn ternary oxide surface cannot be reactivated, PbO2 and BDD can be restored to their initial activity by simple anodic treatment in the potential region of electrolyte decomposition. In fact, during the polarization in this region, complex oxidation reactions leading to the complete incineration of polymeric materials can take place on these electrodes due to electrogenerated hydroxyl radicals. Moreover, it was found that BDD deactivation was less pronounced and its reactivation was faster than that of the other electrodes.

Characterisation of composite SOFC cathodes using electrochemical impedance spectroscopy. Analysis of Pt/YSZ and LSM/YSZ electrodes

The performance of composite electrodes as a function of the electrode composition is investigated experimentally through electrochemical impedance spectroscopy (EIS). In particular, two different composite cathodes are analysed, i.e. Pt/YSZ and LSM/ YSZ. Typical impedance spectra have been obtained and used to evaluate the overall electrode polarisation resistance Rp. The qualitative features are similar for both cathodes; in particular, in both cases the electrode performance (expressed in terms of R p 1 ) shows a dome-shaped curve as a function of the electrode composition. Nevertheless, the quantitative aspects are very different; in particular, the maximum value of R p 1 is much higher for the LSM/YSZ electrode than for the Pt/YSZ one (22 vs. 1.5 S cm 2 ). Also, the composition which gives the maximum performance and the experimental values of the percolation thresholds are different. The reasons for the discrepancies are analysed and discussed. # 2002 Elsevier Science Ltd. All rights reserved.

Electrochemical oxidation of 2-naphthol with in situ electrogenerated active chlorine

Abstract The electrochemical oxidation of 2-naphthol mediated by active chlorine electrogenerated in situ on a Ti–Ru–Sn ternary oxide has been studied by galvanostatic electrolysis under different experimental conditions. Measurements of chemical oxygen demand (COD), HPLC and GC analyses have been used to follow the oxidation. In the absence of NaCl, only a small fraction of 2-naphthol was oxidized by direct electrolysis, while its complete mineralization was obtained in the case of chlorine-mediated electrolysis. In particular, the rate of naphthol oxidation was found to increase with chloride concentration, pH and to be independent of current density. Analysis of oxidation product has shown that initially organochlorinated compounds have been formed which have been further completely oxidized.