A. M. Polcaro

Three-dimensional electrodes for the electrochemical combustion of organic pollutants

Abstract The ability of a fixed bed of carbon pellets to work as anode in destroying chlorophenols (ClPhs) was verified. The applied current is able to continuously regenerate the external active sites of the carbon surface on which oxygen and organic are adsorbed. The low organic coverage degree of carbon, which can be maintained during runs, hinders phenol diffusion to the interior of the pellets: only the external pores are involved in the process. Preliminary runs are also presented at dimensional stable anodes (DSA®) based on Ru–Ti oxides. The results indicate that if a divided electrochemical cell is used, the behaviour of DSA® approaches that of Ti/SnO 2 electrode: the reactant can be oxidised without accumulation of cyclic intermediates, thus limiting the toxicity of the resulting solution.

Electrochemical treatment of phenolic waters in presence of chloride with boron-doped diamond (BDD) anodes: Experimental study and mathematical model

This work deals with an experimental and numerical study on the electrochemical treatment of waters containing phenolic compounds with boron-doped diamond (BDD) anodes. Anodic oxidation of m-cresol, as a model of phenolic compound, was investigated by galvanostatic electrolyses. The electrolyses were carried out under different experimental conditions by using an impinging-jet flow cell inserted in a hydraulic circuit in a closed loop. On the basis of the experimental results a mathematical model was implemented to simulate the effect of the chemistry of organic compounds and solution on the process, in particular the effect of chlorides on the kinetics of m-cresol oxidation. The effect of hydrodynamics of the cell on the mass transfer towards the electrode surface was also considered. The model was validated through comparison with experimental data: the results showed that the proposed model well interpreted the complex effect on removal efficiency of such operative parameters as current density, hydrodynamic of the reactor and chemistry of the solution. The model predictions were utilised to obtain quantitative information on the reaction mechanism, as well as to predict the performance of the process under different operative conditions, by calculating some relevant figures of merit.

Behaviour of a carbon felt flow by electrodes Part I: Mass transfer characteristics

The properties of a carbon felt electrode have been experimentally investigated with special attention to its possible application in the electrochemical recovery of heavy metals. The mass transfer process has been studied by means of the reduction of ferricyanide and cupric ions for a flow-by electrode operating under limiting current conditions. An empirical correlation between the Sherwood and Reynolds numbers has been used to compare the experimental data with those obtained by other authors for different porous electrodes.

The influence of sulphide environment on hydrogen evolution at a stainless steel cathode in alkaline solution

Abstract The kinetics of hydrogen evolution at an AISI 316 cathode in 0.1 M NaOH have been studied by determining the steady-state polarization behaviour and the open-circuit potential decay following interruption of the polarizing current. Electrochemical data have been obtained both for the electrode in stagnant solution and for an impinging jet electrode. The results suggest that the electrode behaviour, at a high mass-transfer rate, is characterized by the kinetics of hydrogen desorption through the molecular recombination path. Moreover, it appears that, in addition to the adsorption on the surface, hydrogen penetration into the layers beneath the surface can also occur. A lowering of the charge needed to change the degree of coverage of adsorbed hydrogen from zero to one and inhibition of the molecular recombination step induced by sulphide chemisorption may explain the observed behaviour when Na 2 S is added to the electrolyte.

Competitive Sorption of Heavy Metal Ions by Soils

An experimental study is presented on heavy metal pollution of soils. In particular, Pb2+, Zn2+, Cd2+ are considered as most representing the pollution of a Sardinian (Italy) area, where important mining activities connected to the extraction of blende and galena have been carried out in the past. Results of batch experiments involving adsorption from mono-component metal solutions are examined showing that at the fixed working pH of 6.5, a fraction of metal was always retained by ion exchange; surface precipitation was assumed to be responsible for the remaining fraction of metal retained. Competitive adsorption is also investigated by performing multicomponent sorption isotherms. The aim of the work was to evaluate the exchangeable fraction of metal retained in the soil, when it is contaminated by multicomponent heavy metal solutions. A mathematical model is presented which, using only parameters from binary adsorption data, is able to predict the fraction of metal retained by ion exchange from multicom...

Electrodeposition of catalysts for hydrogenation of organic molecules : deposition mechanism of Pd on carbon felt

Abstract This paper presents experimental results on electrodeposition of palladium at controlled potential from acidic solutions containing low Pd 2+ concentration. The influence of electrode potential and fluidodynamic of solutions on the velocity of growth and distribution on the fibers of crystallization centres has been discussed,. The hydrogen evolution reaction has been used to evaluate the electrocatalytic activity of the electrodes. Their performance has been found to depend on the palladium deposition conditions.

Tritium recovery from liquid Li17Pb83 alloy blanket material

Abstract Two methods to recover the tritium from the Li 17 Pb 83 liquid breeder used in the breeding blanket design developed at JRC-Ispra for INTOR/NET [1] are outlined and discussed. They are (i) direct tritium pumping from stagnant and stirred breeder, and (ii) tritium extraction from a packed or bubble column by flushing an inert gas in counter-current to the breeder. The lack of experimental data on tritium solubility and diffusion and on other physico-chemical properties of Li 17 Pb 83 do not yet enable us to choose among the two schemes. However, at present the second appears more promising.

Electrochemical reduction of carbonyl compounds at modified carbon felt electrodes

Abstract The reduction of acetophenone and benzaldehyde at carbon felt electrodes, on which Pd and Pt were deposited under the same conditions, is comparatively investigated in ethanol—water solutions. In acid solutions, higher η F values are obtained when the active metal deposited on the fibres is palladium; a different behaviour is noticed at Pt electrocatalysts which, during the benzaldehyde reduction, show a better performance in alkaline solution. The influence of the electrolysis conditions on the selectivity of the reactions is also considered.

Electrodeposition of catalysts for Hydrogenation of Organic Molecules: hydrogenation of benzaldehyde

Abstract Electrocatalytic hydrogenation of benzaldehyde in acid hydroalcoholic solution has been studied at porous electrodes prepared by deposition of palladium on carbon felt. Preliminary results obtained by means of cyclic voltammetries, steady-state current-voltage curves and several series of preparative electrolyses are presented.

Case Studies in the Electrochemical Treatment of Wastewater Containing Organic Pollutants Using BDD

A critical review is presented in this chapter on the possible applications of boron-doped diamond (BDD) as anode material to perform oxidation of organic compounds in aqueous solution. The oxidation of model substances is studied as well as that of the main classes of pollutants, such as phenols, dyes, pesticides and drugs, surfactants, which make some problems of degradation with the traditional wastewater treatments. The presented results indicate that organic compounds refractory to other oxidation techniques are successfully oxidized at BDD, even if the reaction mechanism is differently dependent on the organic compound and the electrolyte composition. Economic considerations reveal that electrochemical oxidations at BDD are less expensive than other advanced oxidation processes, indicating that in the near future this technology can become a competitive treatment for the removal of refractory compounds from wastewater.