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General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Pollution, Traitement et pollution des eaux, Water treatment and pollution, Eaux usées, Wastewaters, Eaux usées industrielles, Industrial wastewaters, Sciences biologiques et medicales, Biological and medical sciences, Sciences biologiques fondamentales et appliquees. Psychologie, Fundamental and applied biological sciences. Psychology, Biotechnologie, Biotechnology, Applications et implications industrielles. Aspects économiques, Industrial applications and implications. Economical aspects, Environnement et pollution, Environment and pollution, Epuration biologique des eaux, Biological treatment of waters, Métal transition, Transition metal, Metal transición, Platinoïde, Platinoid, Platinoide, Anaérobie, Anaerobe, Anaerobio, Aérobie, Aerobe, Aerobio, Bioremédiation, Bioremediation, Biorremediación, Cinétique, Kinetics, Cinética, Consommation énergie, Energy consumption, Consumo energía, DCO, Chemical oxygen demand, Eau usée industrielle, Industrial waste water, Agua servida industrial, Electrocatalyse, Electrocatalysis, Electrocatálisis, Electrode, Electrodes, Electrodo, Epuration biologique, Biological purification, Depuración biológica, Epuration eau usée, Waste water purification, Depuración aguas servidas, Iridium, Iridio, Matériau modifié, Modified material, Material modificado, Mécanisme réaction, Reaction mechanism, Mecanismo reacción, Oxydation, Oxidation, Oxidación, Platine, Platinum, Platino, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Tannerie, Tannery, Tenería, Titane, Titanium, Titanio, combination of biological and electrochemical processes, electro-oxidation, energy consumption, and tannery wastewater treatment

The paper is aimed at defining the best option of a combination of electrochemical and biological processes for tannery wastewater treatment. Kinetic data for the electrochemical process are derived from an extensive experimental study, while those relating to biological processes are taken from the authors' previously published studies or from the literature. Four different options based on a combination of electrochemical oxidation and biological treatment are defined and compared with the traditional tannery wastewater treatment with respect to the total required volume, energy need and the quantity of generated sludge.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Sciences appliquees, Applied sciences, Pollution, Traitement et pollution des eaux, Water treatment and pollution, Eaux usées, Wastewaters, Eaux usées de toute autre origine, Other wastewaters, Métal transition, Transition metal, Metal transición, Anode sacrificielle, Sacrificial anode, Anodo sacrificial, Cinétique, Kinetics, Cinética, DCO, Chemical oxygen demand, Eau usée industrielle, Industrial waste water, Agua servida industrial, Epuration eau usée, Waste water purification, Depuración aguas servidas, Fer, Iron, Hierro, Origine végétale, Plant origin, Origen vegetal, Oxydation, Oxidation, Oxidación, Précipitation chimique, Chemical precipitation, Precipitación química, Réaction Fenton, Fenton reaction, Reacción Fenton, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Spectrométrie UV visible, Ultraviolet visible spectrometry, Espectrometría UV visible, Tanin, Tannin, Tanino, Tannique acide, Tannic acid, electroprecipitation, gallotannic acid, peroxicoagulation, and tanning wastewater

Synthetic solutions containing up to 2000 ppm of gallotannic acid and real wastewater from vegetal tanning processes with values of chemical oxygen demand (COD) exceeding 100 000 ppm were decontaminated by electrolysis using a sacrificial iron anode coupled to either a titanium-platinised or an O2-diffusion cathode. Experiments were performed in the presence of oxidants and oxidation promoters such as air, oxygen and hydrogen peroxide, the latter being directly added to the solution or electrogenerated by the O2-diffusion cathode. COD and UV-visible absorbance evolution showed that tannins are removed from electrolysed solutions down to relatively low values, permitting more than 94% elimination. Partial oxidation of the mother compound generates short-chain by-products (mostly carboxylic acids) responsible for the remaining low COD values. Contaminants (tannins and non-tannins) contained in industrial wastewater were removed by combining electroprecipitation with a Fenton-assisted process; a final oxidation step, carried out on a boron-doped diamond electrode, was performed in order to decrease the COD to very low final values.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Pollution, Pollution du sol et des sédiments, Soil and sediments pollution, Décontamination. Divers, Decontamination. Miscellaneous, Métal transition, Transition metal, Metal transición, Citrique acide, Citric acid, Cítrico ácido, Cuivre, Copper, Cobre, Décontamination, Decontamination, Descontaminación, Ethylèneimine polymère, Polyethylene imine, Etilenoimina polímero, Extraction ion, Ion extraction, Extracción ión, Filtration sur membrane, Membrane filtration, Filtración membrana, Hydroxyacide, Hydroxyacid, Hidroxiácido, Lessivat, Leachate, Lixiviado, Membrane polymère, Polymeric membrane, Membrana polímero, Métal lourd, Heavy metal, Metal pesado, Pollution sol, Soil pollution, Polución suelo, Sol, Soils, Suelo, Solution aqueuse, Aqueous solution, Solución acuosa, Triacide carboxylique, Tricarboxylic acid, Triácido carboxílico, Ultrafiltration, Ultrafiltración, citric acid, contaminated soil, copper removal, polyethylenimine, and polymer-assisted ultrafiltration

The removal of heavy metals from aqueous systems such as wash-solutions of contaminated soil by using Polymer-Assisted Ultrafiltration (PAUF) has been studied. For the extraction of metal ions from contaminated soil citric acid is used as a chelating agent. Cu2+ as metal ion and the polymer polyethylenimine (PEI) as ligand were used in the various experiments. Optimal chemical conditions for copper complexation by citric acid were determined by means of complexation tests. The results showed that citric acid is able to chelate copper ions at pH 5.5, while decomplexation occurs at pH ≤ 2. Maximum bonding capacity (saturation condition) was 0.625 mg Cu2+ per mg citric acid, meaning 2 mol Cu2+ per mol citric acid. Complexation tests in the system polyethylenimine-citric acid-copper showed that the polymer is able to complex the copper-citric acid chelate at pH = 6 while release occurs at pH < 3. The saturation condition was 0.333 mg Cu2+ per mg PEI. The ultrafiltration tests, carried out at three trans-membrane pressures (2, 3 and 4 bar), showed the possibility of using the PAUF technique for copper ion removal from aqueous solutions.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Généralités, General, Sciences appliquees, Applied sciences, Pollution, Traitement et pollution des eaux, Water treatment and pollution, Eaux usées, Wastewaters, Procédés généraux d'épuration, General purification processes, Consommation énergie, Energy consumption, Consumo energía, Effet concentration, Concentration effect, Efecto concentración, Effet milieu, Medium effect, Efecto medio, Efficacité, Efficiency, Eficacia, Electrode, Electrodes, Electrodo, Epuration eau usée, Waste water purification, Depuración aguas servidas, Fer II Ion, Iron II Ions, Hierro II Ión, Graphite, Grafito, Hydrogène Peroxyde, Hydrogen Peroxides, Hidrógeno Peróxido, Hydroxyle, Hydroxyl, Hidroxilo, Hypophosphite, Hypophosphites, Hipofosfito, Mécanisme réaction, Reaction mechanism, Mecanismo reacción, Oxydation, Oxidation, Oxidación, Phosphore Composé, Phosphorus Compounds, Fósforo Compuesto, Radical libre, Free radical, Réaction Fenton, Fenton reaction, Reacción Fenton, Réaction radicalaire, Free radical reaction, Reacción radicalar, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Solution aqueuse, Aqueous solution, Solución acuosa, electro-Fenton, ferrous ions, hydrogen peroxide, hydroxyl radical, molar ratio, and oxidation

An electro-Fenton treatment of a solution containing phosphorus compounds using a graphite electrode is described. Different operating conditions are tested to investigate the influence of the reagent ratio on the oxidative efficiency. Results show that electro-Fenton's reagent is able to provide a powerful conversion of the phosphorous compounds into phosphate. As hydrogen peroxide is continuously provided by the cathodic reduction of oxygen, the crucial step appears to be the iron dosage whose optimal concentration is found in the range 50-150 mg 1-1. Quantitative oxidation is not reached for concentration lower than 50 mg 1-1. Nonetheless, an excess of both iron and hydrogen peroxide in the bulk is found to negatively affect the oxidation yield because of the occurrence of undesired side reactions.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Halogène Composé organique, Halogen Organic compounds, Halógeno Compuesto orgánico, Métal transition, Transition metal, Metal transición, Acétonitrile, Acetonitrile, Acetonitrilo, Argent, Silver, Plata, Composé organique volatil, Volatile organic compound, Compuesto orgánico volátil, DMF, N,N-Dimethylformamide, Dimetilformamida, Dégradation chimique, Chemical degradation, Degradación química, Déshalogénation, Dehalogenation, Deshalogenación, Effet milieu, Medium effect, Efecto medio, Electrocatalyse, Electrocatalysis, Electrocatálisis, Electrode, Electrodes, Electrodo, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Réduction chimique, Chemical reduction, Reducción química, Solvant organique, Organic solvent, Solvente orgánico, Ammonium(tétraéthyl) tétrafluoroborate, Ethane(polychloro), Méthane(polychloro), electrocatalysis, electrochemical degradation, polychloroethanes, polychloromethanes, silver, and volatile organic halides

The electroreduction of polychloromethanes and polychloroethanes has been studied by means of cyclic voltammetry (CV) and preparative electrolysis experiments in acetonitrile (ACN), dimethylformamide (DMF) and their admixtures with water. Silver has been used as cathode material, on account of our extended experience on its well established electrocatalytic activity toward reductive dehalogenation reactions of organic compounds. Polychloromethanes and -ethanes are common chlorinated solvents pertaining to the large family of volatile organic halides (VOH), whose high toxicity, or even carcinogenicity, demands careful treatment of contaminated soils, drinking waters and gaseous emissions. The results confirm the electrocatalytic role of silver and suggest a general route for the development of appropriate degradation processes.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Pollution, Traitement et pollution des eaux, Water treatment and pollution, Eaux usées, Wastewaters, Eaux usées de toute autre origine, Other wastewaters, Agent surface anionique, Anionic surfactant, Agente superficie aniónico, Bore, Boron, Boro, Cinétique, Kinetics, Cinética, Composé quaternaire, Quaternary compound, Compuesto cuaternario, Condition opératoire, Operating conditions, Condición operatoria, Diamant synthétique, Synthetic diamond, Diamante sintético, Débit, Flow rate, Gasto, Electrode, Electrodes, Electrodo, Epuration eau usée, Waste water purification, Depuración aguas servidas, Etain Oxyde, Tin Oxides, Estaño Óxido, Matériau dopé, Doped materials, Oxydation, Oxidation, Oxidación, Ruthénium Oxyde, Ruthenium Oxides, Rutenio Óxido, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Sodium Sulfate, Sodium Sulfates, Sodio Sulfato, Titane Oxyde, Titanium Oxides, Titanio Óxido, Sodium benzènesulfonate(4-dodécyl), BDD anode, Ti-Ru-Sn oxide anode, anionic surfactant, car wash wastewater, and electrochemical oxidation

This study was performed to investigate the electrochemical oxidation of anionic surfactants. In particular, a synthetic solution of sodium dodecyl benzene sulfonate and a real car wash wastewater were treated by galvanostatic electrolysis using a Ti-Ru-Sn ternary oxide and a boron-doped diamond (BDD) anode. Measurements of the Chemical Oxygen Demand (COD) and the concentration of the anionic surfactants were used to follow the oxidation. Using the Ti-Ru-Sn ternary oxide anode, the complete removal of COD and sodium dodecyl benzene sulfonate was obtained only in the presence of chloride ions that act as inorganic mediators. The oxidation rate was almost independent of current density and electrolyte flow rate. In the case of BDD the mineralisation of the sodium dodecyl benzene sulfonate was achieved in all experimental conditions due to reaction with hydroxyl radicals electrogenerated on the diamond surface during electrolysis. The COD removal rate increased with increase in electrolyte flow rate, indicating that the oxidation was mass-transfer controlled. Comparison of the results of the two electrodes showed that chlorine mediated oxidation at the Ti-Ru-Sn ternary oxide anode allowed a faster COD removal of both the synthetic solution and real car wash wastewater.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Métal transition, Transition metal, Metal transición, Anode, Anodo, Charbon actif, Activated carbon, Carbón activado, Composé organique, Organic compounds, Compuesto orgánico, Désactivation, Deactivation, Desactivación, Effet milieu, Medium effect, Efecto medio, Iridium Oxyde, Iridium Oxides, Iridio Óxido, Matériau électrode, Electrode material, Material electrodo, Microscopie électronique balayage, Scanning electron microscopy, Microscopía electrónica barrido, Morphologie, Morphology, Morfología, Oxydation, Oxidation, Oxidación, Phénol, Phenol, Fenol, Platine, Platinum, Platino, Plomb Oxyde, Lead Oxides, Plomo Óxido, Polluant, Pollutant, Contaminante, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Réflexion totale atténuée, Total attenuated reflection, Reflexión total atenuada, Régénération, Regeneration, Regeneración, Sodium Chlorure, Sodium Chlorides, Sodio Cloruro, Sodium Sulfate, Sodium Sulfates, Sodio Sulfato, Solution aqueuse, Aqueous solution, Solución acuosa, Spectrométrie IR, Infrared spectrometry, Espectrometría IR, Spectrométrie UV, Ultraviolet spectrometry, Espectrometría UV, Structure surface, Surface structure, Estructura superficie, Sulfurique acide, Sulfuric acid, Sulfúrico ácido, Tantale Oxyde, Tantalum Oxides, Tantalio Óxido, Titane, Titanium, Titanio, Transformation Fourier, Fourier transformation, Transformación Fourier, Voltammétrie cyclique, Cyclic voltammetry, Voltametría cíclica, PbO2, Pt, Ti/IrO2/ Ta2O5, activated carbon, anode, deactivation, electro-oxidation, phenol, regeneration, and voltammetry

Electro-oxidation tests with different electrolytes (Na2SO4, NaCl, H2SO4) and anode types (Pt, Ti lined with Ir and Ta oxides, PbO2, activated carbon) were performed on aqueous solutions containing phenol to assess the mechanism and nature of electrode deactivation phenomena. For the Pt electrode, the nature of the electro-deposited organic species was investigated by ATR-FTIR and FESEM-EDS analyses, which showed adsorption of intermediate oxidation products (e.g. benzoquinone, hydroquinone) is likely responsible for the early deactivation stages. Conversely, in the longer term, formation of polymeric films is promoted. Potentiostatic tests showed that anode regeneration can be achieved by anodic polarisation above 1.1 V (vs Hg/Hg2SO4). This reactivation was found to be easier in the presence of significant amounts of chloride ions. Conversely, the deactivated state is maintained for the Ti/IrO2/Ta2O5 electrode even though anodic polarisation at high positive potentials is applied. Cyclic voltammetric curves on PbO2 electrodes did not provide satisfactory results as the intensity of the lead-dioxide reduction peak was so high that peaks for phenol oxidation were hardly detectable. Finally, the activated carbon based electrode was found to be promising as it enables simultaneous adsorption of the organic pollutant and oxidation of the pollutant itself to constitute a sort of self-regenerating adsorber unit.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Energie, Energy, Energie. Utilisation thermique des combustibles, Energy. Thermal use of fuels, Appareils de production et de conversion d'énergie: énergie thermique, énergie électrique, énergie mécanique, etc, Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc, Piles à combustible, Fuel cells, Cathode, Cátodo, Composé minéral, Inorganic compound, Compuesto inorgánico, Condition opératoire, Operating conditions, Condición operatoria, Effet température, Temperature effect, Efecto temperatura, Electrode, Electrodes, Electrodo, Electrolyte solide, Solid electrolyte, Electrólito sólido, Energie activation, Activation energy, Energía activación, Lanthane Manganite, Lanthanum Manganites, Lantano Manganito, Oxygène, Oxygen, Oxígeno, Pile combustible oxyde solide, Solid oxide fuel cell, Pila combustible oxido sólido, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Réduction chimique, Chemical reduction, Reducción química, Spectrométrie impédance électrochimique, Electrochemical impedance spectroscopy, Strontium Manganite, Strontium Manganites, Estroncio Manganito, Yttrium Oxyde, Yttrium Oxides, Ytrio Óxido, Zircone stabilisée, Stabilized zirconia, Zircona estabilizada, composite cathodes, electrochemical measurements, impedance spectroscopy, and solid oxide fuel cells

The electrochemical characteristics of composite cathodes consisting of Lanthanum Strontium Manganite (LSM) and Yttria Stabilised Zirconia (YSZ) have been analysed in order to emphasise the opportunity offered by these electrodes in the attempt to reduce the temperature of solid oxide fuel cells. Impedance analysis and potentiody-namic polarisation have been used as tools to evaluate the main electrochemical parameters and the results show that a volume ratio between LSM and YSZ close to 1 gives the best electrochemical activity because of the extension of the three phase boundary (TPB) in the electrode. Electrodes of this composition were subjected to high current load to verify the stability of the electrochemical performance and the results confirmed good cathode reliability.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Electrode gaz, Gas electrode, Electrodo gas, Electrode, Electrodes, Electrodo, Etude comparative, Comparative study, Estudio comparativo, Graphite, Grafito, Hydrogène Peroxyde, Hydrogen Peroxides, Hidrógeno Peróxido, Hydroxyle, Hydroxyl, Hidroxilo, Hypophosphite, Hypophosphites, Hipofosfito, Oxydation, Oxidation, Oxidación, Oxygène, Oxygen, Oxígeno, Phosphore Composé, Phosphorus Compounds, Fósforo Compuesto, Radical libre, Free radical, Réaction Fenton, Fenton reaction, Reacción Fenton, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Réduction chimique, Chemical reduction, Reducción química, Solution aqueuse, Aqueous solution, Solución acuosa, Fenton's oxidation, gas diffusion electrode, graphite electrode, hydrogen peroxide, and hydroxyl radical

This work studies the production of hydrogen peroxide through the cathodic reduction of oxygen in acidic medium, by comparing the results obtained using a commercial graphite and a gas diffusion electrode. A low pH was required to allow the application of hydrogen peroxide generation to an electro-Fenton process. The influence of applied potential and the gas flow composition were investigated. The gas diffusion electrode demonstrates a higher selectivity for hydrogen peroxide production, without significantly compromising the iron regeneration, thus making its successful application to a cathodic Fenton-like treatment, possible. Unlike the graphite cathode, the gas diffusion cathode also proved to be effective in the air flow.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Etude des interfaces, Study of interfaces, Dépôt électrolytique, Electrodeposition, Sciences appliquees, Applied sciences, Pollution, Traitement et pollution des eaux, Water treatment and pollution, Eaux usées, Wastewaters, Procédés généraux d'épuration, General purification processes, Métal transition, Transition metal, Metal transición, Batterie acide plomb, Lead acid batteries, Carbone, Carbon, Carbono, Cinétique, Kinetics, Cinética, Dépôt électrolytique, Electrodeposition, Depósito electrolítico, Eau usée industrielle, Industrial waste water, Agua servida industrial, Electrode, Electrodes, Electrodo, Epuration eau usée, Waste water purification, Depuración aguas servidas, Graphite, Grafito, Mécanisme réaction, Reaction mechanism, Mecanismo reacción, Oxydation, Oxidation, Oxidación, Platine, Platinum, Platino, Plomb Oxyde, Lead Oxides, Plomo Óxido, Plomb, Lead, Plomo, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Récupération, Recovery, Recuperación, Réduction chimique, Chemical reduction, Reducción química, felt electrodes, lead dioxide, lead(II), lead, oxidation, and reduction

Results are reported of experiments and modelling of cathodic Pb and anodic PbO2 electrodeposition, aimed at developing a process using both reactions simultaneously for treating aqueous effluents from lead-acid battery recycling plants. Pb(II) solubilities and equilibrium potentials were calculated as functions of pH and sulfate activities. Using kinetic parameters from the literature or determined experimentally, models were developed for current density-potential and current efficiency-potential relationships, together with the current density dependence of specific electrical energy consumptions for Pb(II) recovery. Experimental current density-potential and charge efficiency-potential relationships were in broad agreement with model predictions, with near unity current efficiencies for mass transport controlled PbO2 deposition from electrolytes containing 1 mol Pb(II) m-3 at pH 12. However, charge efficiencies for cathodic deposition of lead were typically 0.2 for 1 mol Pb(II) m-3 + 1 mol O2 (aq) m-3; removal of dissolved oxygen was predicted and determined to increase current efficiencies to near unity. Pb(II) concentrations were depleted to <60 ppb in a batch recycle reactor system with graphite felt anodes and graphite or titanium felt cathodes. Simultaneous cathodic Pb and anodic PbO2 electrodeposition resulted in more rapid Pb(II) depletion than for either reaction separately.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Bore, Boron, Boro, Diamant, Diamond, Diamante, Electrode, Electrodes, Electrodo, Halogénophénols, Halophenols, Halofenoles, Matériau dopé, Doped materials, Minéralisation, Mineralization, Mineralización, Oxydation, Oxidation, Oxidación, Phénol(perchloro), Pentachlorophenol, Polluant, Pollutant, Contaminante, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, diamond electrodes, electrochemical combustion, electrooxidation, and pentachlorophenol

The influence of electrode potential on pentachlorophenol (PCP) oxidation on boron doped diamond (BDD) electrodes in a 0.1 mol L-1 Britton-Robinson buffer (pH 5.5) is described. Controlled potential electrolyses were carried at 0.9, 2.0 and 3.0 V vs Ag/AgCl and the solutions analysed by square wave voltammetry, high performance liquid chromatography, chloride ion selective electrode and spectroscopy in the ultraviolet-visible region. At low positive potential (0.9 V), the formation of an adherent film on the electrode surface involving the transference of 1 electron per PCP molecule was observed. The film was identified as the dimer 2,3,4,5,6-pentachloro-4-pentachlorophenoxy-2,5-cyclohexadienone and the current efficiency was as high as 90%. At potentials close to the onset of O2 evolution (2.0 V), the formation of the corresponding quinone (p-tetrachlorobenzoquinone) was detected at the beginning of the process. This was followed by further oxidation to the hydroxy-benzoquinone with a practically quantitative yield. Electrolyses carried out well into the region of oxygen evolution (3.0 V) lead to the electrochemical combustion of PCP to CO2 and H2O as well as to the release into solution of 5 Cl- ions per PCP molecule destroyed.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Généralités, General, Cellule électrolyse, Electrolysis cell, Célula electrolisis, Electrode tournante, Rotating electrode, Electrodo giratorio, Epuration eau usée, Waste water purification, Depuración aguas servidas, Particule, Particle, Partícula, Réacteur électrochimique, Electrochemical reactor, Reactor electroquímico, Simulation mathématique, Mathematical simulation, Simulación matemática, Traitement eau, Water treatment, Tratamiento agua, cascade of reactors, electrochemical reactor, mathematical model, rotating drum, three-dimensional electrode, and water treatment

The cascade variant of the vertically moving particle bed (VMPB) cell represents a novel type of electrochemical cell for technological and wastewater treatment using a rotating three-dimensional electrode. It is characterized by a high surface area, high space-time yield and simple handling. These properties have been achieved by electrode rotation, a cascade arrangement of single rotating drums and automatic particle exchange between neighbouring rotating drums. Two types of mathematical model have been developed. They differ with regard to the degree of complexity and the numerical mathematics method used to solve the equations derived. The results obtained by the two types of model are compared. The influence of the main process parameters is studied for the model case of a single drum cell. The viability of the individual model types for evaluating the influence of the operation parameters of the cell on its performance is discussed.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Etude des interfaces, Study of interfaces, Phénomènes de transport, Transport phenomena, Equation transport, Transport equation, Ecuación transporte, Nombre Schmidt, Schmidt number, Número Schmidt, Nombre transport, Transport number, Número transporte, Phénomène transport, Transport process, Fenómeno transporte, Plaque parallèle, Parallel plate, Placa paralela, Réacteur électrochimique, Electrochemical reactor, Reactor electroquímico, Simulation numérique, Numerical simulation, Simulación numérica, Transfert ion, Ion transfer, Transferencia ión, Transfert masse, Mass transfer, Transferencia masa, Transport turbulent, Turbulent transport, Transporte turbulento, Turbulence, Turbulencia, high Schmidt number, k-ω model, multi-ion mass transfer, parallel plate reactor, and turbulence

Laminar and turbulent mass transfer in a parallel plate reactor at high Schmidt number obtained from numerical simulation is compared with literature data. In a first step, the fluid flow is determined numerically in the reactor by solving the Navier-Stokes equations. For turbulent flow, a low Reynolds number k-ω model is used to calculate the turbulent viscosity. Using the obtained flow field and turbulent viscosity, the current density distribution is calculated for different flow velocities by solving the equations describing the transport of multiple ions due to diffusion, convection and migration. For the laminar case, a very good agreement with literature data is obtained. For turbulent flow, different numerical models for turbulent mass transfer are proposed in the literature. A detailed study of the behaviour close to the wall of these different turbulence models is presented, together with a comparison of the calculated results with literature correlations. This allows identification of the benefits and disadvantages of each of the turbulence models for the numerical calculation of mass transfer at high Schmidt numbers in a parallel plate reactor.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Divers (électroosmose, électrophorèse, électrochromisme, électrocristallisation, ...), Miscellaneous (electroosmosis, electrophoresis, electrochromism, electrocrystallization, ...), Sciences appliquees, Applied sciences, Pollution, Traitement et pollution des eaux, Water treatment and pollution, Eaux usées, Wastewaters, Procédés généraux d'épuration, General purification processes, Coefficient diffusion, Diffusion coefficient, Coeficiente difusión, Cuivre ion, Copper ion, Cobre ión, Echange ion, Ion exchange, Cambio iónico, Electrodialyse, Electrodialysis, Electrodiálisis, Enlèvement, Removal, Toma, Epuration eau usée, Waste water purification, Depuración aguas servidas, Méthode électrochimique, Electrochemical method, Método electroquímico, Phénomène transport, Transport process, Fenómeno transporte, Solution diluée, Dilute solution, Solución diluida, Transfert ion, Ion transfer, Transferencia ión, copper ions, electrodialysis, ion exchange, transport phenomena, and treatment of dilute solutions

Hybrid ion exchange electrodialysis processes allow the removal of metal ions from dilute waste liquids and the recovery of more concentrated solutions. The work reported here was aimed at investigating the two steps in the treatment process, namely, adsorption of metal ions onto the packed bed of resin and electromigration (i.e., the transport of these ions in the complex system under the applied electrical field). The case of copper sulfate was investigated. Dowex resins with a cross-linking degree of 2 and 8% were used. The flux of copper through the resin bed and the current efficiency for ion transfer to the cathode compartment were determined as a function of potential gradient and copper ionic fraction in the bed. Apparent diffusion coefficients of Cu2+ in the overall system were deduced from the experimental data.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Electrodes: préparations et propriétés, Electrodes: preparations and properties, Autres électrodes, Other electrodes, Bore, Boron, Boro, Couple redox, Redox couple, Pareja redox, Diamant, Diamond, Diamante, Dépôt chimique phase vapeur, Chemical vapor deposition, Depósito químico fase vapor, Electrode, Electrodes, Electrodo, Impédance électrique, Electrical impedance, Impedancia eléctrica, Matériau dopé, Doped materials, Phénomène transport, Transport process, Fenómeno transporte, Potassium Hexacyanoferrate, Potassium Hexacyanoferrates, Potasio Hexacianoferrato, Réaction réversible, Reversible reaction, Reacción reversible, Schéma équivalent, Equivalent circuit, Esquema equivalente, Transfert charge, Charge transfer, Transferencia carga, boron doped diamond, diamond electrodes, impedance spectroscopy, partial blocking, and reversible charge transfer

The electrochemical behaviour of reversible charge transfer reactions on boron doped diamond (BDD) was studied by cyclic voltammetry and electrochemical impedance spectroscopy using rotating disc electrodes under defined convection. Diamond films of 5 μm thickness with doping levels of 200, 3000 and 6000 ppm were prepared by hot filament chemical vapour deposition on niobium substrate. The electrochemical measurements were carried out on BDD electrodes in deaerated 0.5 M Na2SO4 + 5 mM K3[Fe(CN)6]/K4[Fe(CN)6] solution at rotation frequencies 0 < frot < 4000 rpm. Comparative measurements were carried out on an active Pt electrode. The BDD electrodes exhibit distinct irreversibilities indicated by a larger peak potential difference in the cyclic voltammograms, lower diffusion limiting current densities and an additional impedance element at high frequencies. Mechanical polishing with carbon fleece and SiC paper strongly affects the irreversible behaviour of the BDD electrodes. The experimental results are explained by a partial blocking of the diamond surface with reversible charge transfer at active sites. The impedance spectra are analysed quantitatively using a transport impedance model for reversible reactions on partially blocked electrode surfaces.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Sciences appliquees, Applied sciences, Pollution, Traitement et pollution des eaux, Water treatment and pollution, Eaux usées, Wastewaters, Procédés généraux d'épuration, General purification processes, Composé organique, Organic compounds, Compuesto orgánico, Débromation, Debromination, Desbromación, Déshalogénation, Dehalogenation, Deshalogenación, Electrolyte solide polymère, Polymer solid electrolyte, Electrólito sólido polímero, Epuration eau usée, Waste water purification, Depuración aguas servidas, Etude expérimentale, Experimental study, Estudio experimental, Halogénophénols, Halophenols, Halofenoles, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Réduction chimique, Chemical reduction, Reducción química, Phénol(2,4-dibromo), 2,4-dibromophenol (DBP), electrochemical reduction, hydrodehalogenation (HDH), and solid polymer electrolyte cells

The electrochemical hydrodehalogenation (HDH) of 2,4-dibromophenol (DBP) has been carried out by electrochemical reduction in H-cells and solid polymer electrolyte (SPE) cells using catalysed cathodes. The electrochemical process gave high conversions of up to 95%, high selectivities of up to 98%, high current efficiencies of up to 98.5% and energy consumption as low as 2.2 kW h (kg DBP)-1. The type of the catalyst plays a decisive role in the efficiency of the HDH of DBP, with palladium being an attractive material. The effect of current density, DBP concentration, supporting electrolyte and temperature, on the HDH is reported.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Sciences appliquees, Applied sciences, Pollution, Traitement et pollution des eaux, Water treatment and pollution, Eaux usées, Wastewaters, Procédés généraux d'épuration, General purification processes, Bore, Boron, Boro, Cinétique, Kinetics, Cinética, Composé organique, Organic compounds, Compuesto orgánico, Diamant, Diamond, Diamante, Electrode, Electrodes, Electrodo, Epuration eau usée, Waste water purification, Depuración aguas servidas, Matériau dopé, Doped materials, Oxydation, Oxidation, Oxidación, Phénol, Phenol, Fenol, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Traitement électrochimique, Electrochemical treatment, Tratamiento electroquímico, Transfert masse, Mass transfer, Transferencia masa, BDD anodes, mass transfer, phenol oxidation, and wastewater treatment

This work investigates the performance of BDD electrodes during oxidation of aqueous solutions of phenol. The main reaction intermediates are identified, the effect of operating conditions on the faradic yield of the process, and the degree of mineralization achievable under different experimental conditions are evaluated. Due to the crucial role of mass transfer in the process, an impinging jet cell is used for the experiments. The results indicate that if a minimum value of current density is imposed, suitable initial conditions can be set at which the removal of the reactant is always under mass transfer control and the process is carried out at a faradic yield of about unity, up to the near-complete disappearance of total organic load. High current density and high mass transfer coefficient must be used in order to carry out the process with high space-time yield. The performance of BDD is compared to that obtained at Ti/RuO2 anodes.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Sciences appliquees, Applied sciences, Pollution, Traitement et pollution des eaux, Water treatment and pollution, Eaux usées, Wastewaters, Procédés généraux d'épuration, General purification processes, Anthraquinone dérivé, Anthraquinone derivatives, Antraquinona derivado, Colorant cuve, Vat dye, Colorante cuba, Colorant indigoïde, Indigoid dye, Colorante indigo, Electrode, Electrodes, Electrodo, Graphite, Grafito, Lit fixe, Fixed bed, Lecho fijo, Lit fluidisé, Fluidized bed, Lecho fluidizado, Matériau modifié, Modified material, Material modificado, Métal noble, Noble metal, Metal noble, Prétraitement, Pretreatment, Pretratamiento, Quinone, Quinona, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Réduction chimique, Chemical reduction, Reducción química, Traitement chimique, Chemical treatment, Tratamiento químico, Traitement surface, Surface treatment, Tratamiento superficie, anthraquinone, electrochemical reduction, fixed bed, graphite, indigo, modified electrode, quinone, and vat dyes

Reducing agents required in the dyeing process for vat and sulfur dyes cannot be recycled and lead to problematic waste products. The electrochemical reduction of indigo on a fixed bed cathode consisting of graphite granules has been investigated by spectrophotometric experiments in laboratory cells. Experiments yield information about the kinetics and show the possibility of this process for production of water soluble leuco indigo, which offers environmental benefits. The influence of noble metals deposited on the granules and of different pretreatment methods of the graphite is demonstrated. In addition, the immobilization of quinoid molecules on the graphite surface has been investigated.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Sciences appliquees, Applied sciences, Pollution, Traitement et pollution des eaux, Water treatment and pollution, Eaux usées, Wastewaters, Procédés généraux d'épuration, General purification processes, Bore, Boron, Boro, Cinétique, Kinetics, Cinética, Diamant, Diamond, Diamante, Electrode, Electrodes, Electrodo, Epuration eau usée, Waste water purification, Depuración aguas servidas, Halogénophénols, Halophenols, Halofenoles, Matériau dopé, Doped materials, Mécanisme réaction, Reaction mechanism, Mecanismo reacción, Oxydation, Oxidation, Oxidación, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Phénol(chloro), boron-doped diamond, chlorophenols, electrochemical oxidation, and wastes

The electrochemical oxidation of 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol aqueous wastes using boron-doped diamond electrodes was studied. This treatment led to complete mineralization of the wastes regardless of the operating conditions. A simple mechanistic model is consistent with the voltammetric and electrolysis results. According to this model, the electrochemical treatment of chlorophenol aqueous wastes involves the anodic and cathodic release of chlorine followed by the formation of non-chlorinated aromatic intermediates. Subsequent cleavage of the aromatic ring gives rise to non-chlorinated carboxylic acids. Chlorine atoms arising from the hydrodehalogenation of the chlorophenols are converted into more oxidized molecules at the anode. These molecules react with unsaturated C4 carboxylic acid to finally yield trichloroacetic acid through a haloform reaction. The non-chlorinated organic acids are ultimately oxidized to carbon dioxide and the trichloroacetic acid into carbon dioxide and volatile organo-chlorinated molecules. Both direct and mediated electrochemical oxidation processes are involved in the electrochemical treatment of chlorophenols.

General chemistry, physical chemistry, Chimie générale, chimie physique, Electrical engineering, Electrotechnique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Electrochimie, Electrochemistry, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Electrolyse, Electrolysis, Electrólisis, Electrolyte solide polymère, Polymer solid electrolyte, Electrólito sólido polímero, Membrane échangeuse ion, Ion exchange membrane, Membrana cambiadora iónica, Réaction électrochimique, Electrochemical reaction, Reacción electroquímica, Synthèse chimique, Chemical synthesis, Síntesis química, SPE electrolysis method, electro-organic synthesis, electro-osmotic stream, ion exchange membrane, and solid polymer electrolyte

The application of ion exchange membranes as solid polymer electrolytes (SPE) in fuel cells is state-of-the-art. This technology needs no supporting electrolyte; consequently it can be applied for electro-organic syntheses in order to save process steps. In this case the process is not predetermined to a maximized energy efficiency so that the selection of the cell design, of the electrode materials and of the operating conditions can be focused on a high selectivity of the electrode reactions. The electro-osmotic stream, which is caused by the solvation shells of the ions during their migration through the membrane, and hence is a typical property of SPE technology, has a significant effect on the electrode reactions. It generates enhanced mass transfer at the electrodes, which is beneficial for reaction selectivity. It can be influenced by the choice of, and possibly by the preparation of, the membrane. An additional remarkable advantage of SPE technology is the exceptional long durability of oxide coated electrodes. By combination of several process engineering methods stable operation of SPE cells has been realized, even for examples of non-aqueous reaction systems. Experiments up to 6000 h duration and in cells of up to 250 cm2 membrane area show the potential for industrial application.