Enric Brillas

University of Barcelona, Barcino, Catalonia, Spain

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Publications (226)430.88 Total impact

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    ABSTRACT: Pt and Pt–Ru shells on Cu cores supported on Vulcan carbon XC72R have been synthesized and tested as possible anode electrocatalysts for polymer electrolyte fuel cells. Pt(Cu)/C was prepared by Cu electrodeposition on the black carbon support at constant potential followed by Pt deposition on Cu by galvanic exchange, whereas Pt–Ru(Cu)/C was prepared by spontaneous deposition of Ru species on Pt(Cu)/C. The corresponding cyclic voltammograms in 0.5 M H2SO4 solution showed the hydrogen adsorption/desorption peaks and no Cu oxidation. The respective CO stripping peak potentials of Pt(Cu)/C and Pt–Ru(Cu)/C were about 0.1 and 0.2 V more negative than those corresponding to Pt/C and Ru-decorated Pt/C. The best conditions for CO oxidation were found for Cu deposition potentials between −0.2 and −0.4 V vs. Ag/AgCl/KCl(sat). The Pt economy of the Pt–Ru(Cu)/C system was proved for the methanol oxidation, with specific currents more than twice those obtained on the Ru-decorated commercial Pt/C catalysts.
    International Journal of Hydrogen Energy 08/2014; 39(24):12859–12869. · 3.55 Impact Factor
  • José L Nava, Ignasi Sirés, Enric Brillas
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    ABSTRACT: This paper compares the performance of 2D (plate) and 3D (mesh) boron-doped diamond (BDD) electrodes, fitted into a filter-press reactor, during the electrochemical incineration of indigo textile dye as a model organic compound in chloride medium. The electrolyses were carried out in the FM01-LC reactor at mean fluid velocities between 0.9 ≤ u ≤ 10.4 and 1.2 ≤ u ≤ 13.9 cm s(-1) for the 2D BDD and the 3D BDD electrodes, respectively, at current densities of 5.63 and 15 mA cm(-2). The oxidation of the organic matter was promoted, on the one hand, via the physisorbed hydroxyl radicals (BDD(([Symbol: see text])OH)) formed from water oxidation at the BDD surface and, on the other hand, via active chlorine formed from the oxidation of chloride ions on BDD. The performance of 2D BDD and 3D BDD electrodes in terms of current efficiency, energy consumption, and charge passage during the treatments is discussed.
    Environmental Science and Pollution Research 04/2014; · 2.76 Impact Factor
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    ABSTRACT: In recent years, new advanced oxidation processes based on the electrochemical technology, the so-called electrochemical advanced oxidation processes (EAOPs), have been developed for the prevention and remediation of environmental pollution, especially focusing on water streams. These methods are based on the electrochemical generation of a very powerful oxidizing agent, such as the hydroxyl radical ((•)OH) in solution, which is then able to destroy organics up to their mineralization. EAOPs include heterogeneous processes like anodic oxidation and photoelectrocatalysis methods, in which (•)OH are generated at the anode surface either electrochemically or photochemically, and homogeneous processes like electro-Fenton, photoelectro-Fenton, and sonoelectrolysis, in which (•)OH are produced in the bulk solution. This paper presents a general overview of the application of EAOPs on the removal of aqueous organic pollutants, first reviewing the most recent works and then looking to the future. A global perspective on the fundamentals and experimental setups is offered, and laboratory-scale and pilot-scale experiments are examined and discussed.
    Environmental Science and Pollution Research 04/2014; · 2.76 Impact Factor
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    ABSTRACT: The degradation of 230 mL of a 0.6-mM sulfanilamide solution in 0.05 M Na2SO4 of pH 3.0 has been studied by electro-Fenton process. The electrolytic cell contained either a Pt or boron-doped diamond (BDD) anode and a carbon-felt cathode. Under these conditions, organics are oxidized by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between initially added (and then electrochemically regenerated) Fe(2+) and cathodically generated H2O2. From the decay of sulfanilamide concentration determined by reversed-phase liquid chromatography, an optimum Fe(2+) concentration of 0.20 mM in both cells was found. The drug disappeared more rapidly using BDD than Pt, and, in both cases, it was more quickly removed with raising applied current. Almost total mineralization was achieved using the BDD/carbon-felt cell, whereas the alternative use of Pt anode led to a slightly lower mineralization degree. In both cells, the degradation rate was accelerated at higher current but with the concomitant fall of mineralization current efficiency due to the greater increase in rate of the parasitic reactions of hydroxyl radicals. Reversed-phase liquid chromatography allowed the identification of catechol, resorcinol, hydroquinone, p-benzoquinone, and 1,2,4-trihydroxybenzene as aromatic intermediates, whereas ion exclusion chromatography revealed the formation of malic, maleic, fumaric, acetic, oxalic, formic, and oxamic acids. NH4 (+), NO3 (-), and SO4 (2-) ions were released during the electro-Fenton process. A plausible reaction sequence for sulfanilamide mineralization involving all detected intermediates has been proposed. The toxicity of the solution was assessed from the Vibrio fischeri bacteria luminescence inhibition. Although it acquired its maximum value at short electrolysis time, the solution was completely detoxified at the end of the electro-Fenton treatment, regardless of the anode used.
    Environmental Science and Pollution Research 04/2014; · 2.76 Impact Factor
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    ABSTRACT: Dairy wastewater is characterized by a high content of hardly biodegradable dissolved, colloidal, and suspended organic matter. This work firstly investigates the performance of two individual electrochemical treatments, namely electrocoagulation (EC) and electro-oxidation (EO), in order to finally assess the mineralization ability of a sequential EC/EO process. EC with an Al anode was employed as a primary pretreatment for the conditioning of 800 mL of wastewater. A complete reduction of turbidity, as well as 90 and 81 % of chemical oxygen demand (COD) and total organic carbon (TOC) removal, respectively, were achieved after 120 min of EC at 9.09 mA cm(-2). For EO, two kinds of dimensionally stable anodes (DSA) electrodes (Ti/IrO2-Ta2O5 and Ti/IrO2-SnO2-Sb2O5) were prepared by the Pechini method, obtaining homogeneous coatings with uniform composition and high roughness. The (·)OH formed at the DSA surface from H2O oxidation were not detected by electron spin resonance. However, their indirect determination by means of H2O2 measurements revealed that Ti/IrO2-SnO2-Sb2O5 is able to produce partially physisorbed radicals. Since the characterization of the wastewater revealed the presence of indole derivatives, preliminary bulk electrolyses were done in ultrapure water containing 1 mM indole in sulfate and/or chloride media. The performance of EO with the Ti/IrO2-Ta2O5 anode was evaluated from the TOC removal and the UV/Vis absorbance decay. The mineralization was very poor in 0.05 M Na2SO4, whereas it increased considerably at a greater Cl(-) content, meaning that the oxidation mediated by electrogenerated species such as Cl2, HClO, and/or ClO(-) competes and even predominates over the (·)OH-mediated oxidation. The EO treatment of EC-pretreated dairy wastewater allowed obtaining a global 98 % TOC removal, decreasing from 1,062 to <30 mg L(-1).
    Environmental Science and Pollution Research 03/2014; · 2.76 Impact Factor
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    ABSTRACT: Background Based on the promising results obtained at laboratory scale upon a two-step electrochemical treatment of Tartrazine solutions by electrocoagulation (EC) coupled with electrochemical advanced oxidation processes (EAOPs), this work addresses its scale-up to degrade 1.85 dm3 solutions of this dye. Monopolar and bipolar configurations have been compared in EC. The effect of supporting electrolyte, pH, applied current, dye concentration and electrolysis time has been assessed. ResultsEC with four Fe electrodes was firstly optimized for the treatment of 278 mg dm−3 Tartrazine solutions. The bipolar configuration in series led to an enhanced coagulation due to the larger electrode consumption. Solutions with 0.05 mol dm−3 NaCl at pH 6.3 were quickly decolorized with 60% total organic carbon removal, being more convenient than Na2SO4 and NaNO3 electrolytes due to the synergistic action of coagulation and oxidation by active chlorine. Among the EAOPs, carried out with a Ti/IrO2-RuO2 anode and an air-diffusion cathode to electrogenerate H2O2, electro-Fenton (EF) with 0.5 mmol dm−3 Fe2+ was much better than electro-oxidation owing to the oxidative action of active chlorine and •OH formed in the bulk from Fenton's reaction. Photoelectro-Fenton (PEF) was even superior by the additional photolysis of by-products under incident UVA photons. Conclusions The use of an EC reactor in bipolar configuration for 12.5 min at 1.50 A followed by PEF treatment for 360 min at 1.50-2.00 A ensured a mineralization > 90%, which encourages further optimization at larger scale for the treatment of a variety of organic pollutants in real wastewaters.
    Journal of Chemical Technology & Biotechnology 02/2014; · 2.50 Impact Factor
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    ABSTRACT: In this paper we report the spectral properties of the stable radical adducts 1·-3· which are formed by an electron donor moiety, the carbazole ring, and an electron acceptor moiety, the polychlorotriphenylmethyl radical. The molecular structure of radical adduct 1· in the crystalline state shows a torsion angle of approximately 90deg between the phenyl and the carbazole rings due to steric interactions. They exhibit a charge transfer band in the visible range of the electronic spectrum. All of them are chemically oxidized with copper(II) perchlorate to the respective cation species which show a strong charge transfer band into the near-infrared region of the spectrum. Radical adducts 1·-3· and the corresponding stable oxidized species 1+- 3+ are real organic mixed-valence compounds due to the open-shell nature of their electronic structure. Charge transfer bands of the cation species are stronger and batochromically shifted with respect to those of the neutral species due to the greater acceptor ability of the positively charged central carbon atom of the triphenylmethyl moiety. The cationic species 1+-3+ are diamagnetic due to the absence of signal in the EPR spectrum in acetonitrile solution at room temperature, but they show an intense and unique band in frozen solutions (183 K).
    The Journal of Organic Chemistry 01/2014; · 4.56 Impact Factor
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    ABSTRACT: Here, 2.5 L of solutions of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide of pH 3.0 have been degraded by electrochemical oxidation (EO) and electro-Fenton (EF) using a recirculation flow plant equipped with a single Pt/air-diffusion or BDD/BDD cell containing electrodes of 20 cm2 area. In EO, organics were mainly oxidized by ●OH formed at the anode surface from water oxidation, whereas in EF they were also destroyed in the bulk by ●OH generated from Fenton’s reaction between added Fe2+ and H2O2 produced at the cathode. In both treatments, the use of a single BDD/BDD cell always allowed larger decontamination due to the higher ability of ●OH at the BDD surface to mineralize organic intermediates. The most potent EF process with this cell gave 59% mineralization with 23% efficiency and 0.42 kWh g-1 TOC specific energy after 300 min at 0.5 A. The coupling of Pt/air-diffusion and BDD/BDD cells with equal individual current in EF led to similar mineralization degree to that found for the Pt/air-diffusion one at the same total current, but in much shorter time. The effect of current on the mineralization rate, mineralization current efficiency and specific energy of each method was examined. The influence of herbicide concentration on the EF performance of the coupled cell at 2.0 A/2.0 A was also studied and 83% mineralization was obtained as maximal for 276 mg L-1 2,4-D. The herbicide decay always obeyed a pseudo-first-order reaction. A mixture of short-linear carboxylic acids was detected in all final electrolyzed solutions, which were the major organic by-products generated using the single BDD/BDD cell but formed in minor proportion in the EF processes with the Pt/air-diffusion and coupled ones.
    Journal of Electroanalytical Chemistry. 01/2014;
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    ABSTRACT: Solutions of 236 mg dm−3 Acid Red 1 (AR1), an azo dye widely used in textile dying industries, at pH 3.0 have been comparatively treated by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) at constant current density (j). Assays were performed with a stirred tank reactor equipped with a Pt or boron-doped diamond (BDD) anode and an air-diffusion cathode for H2O2 generation from O2 reduction. The main oxidizing agents were hydroxyl radicals produced at the anode from water oxidation in all methods and in the bulk from Fenton's reaction between generated H2O2 and 0.5 mmol dm−3 Fe2+ in EF and PEF. For each anode, higher oxidation power was found in the sequence AO-H2O2 < EF < PEF. The oxidation ability of the BDD anode was always superior to that of Pt. Faster and similar decolorization efficiency was achieved in EF and PEF owing to the quicker destruction of aromatics with hydroxyl radicals produced in the bulk. The PEF process with BDD was the most potent method yielding almost total mineralization due to the additional rapid photolysis of recalcitrant intermediates like Fe(III)-carboxylate complexes under UVA irradiation. The increase in j always enhanced the decolorization and mineralization processes because of the greater production of hydroxyl radicals, but decreases the mineralization current efficiency. A total of 11 aromatic intermediates, 15 hydroxylated compounds, 13 desulfonated derivatives and 7 short-linear carboxylic acids were identified. NH4+, NO3− and SO42− ions were released during azo dye degradation. From the products detected, a comprehensive reaction sequence for AR1 mineralization is proposed. The relationship between decolorization, mineralization and products formed is finally discussed.
    Electrochimica Acta. 01/2014; 142:276–288.
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    ABSTRACT: A novel sequential electrochemical treatment consisting in an electrocoagulation (EC) pre-treatment and the subsequent advanced oxidation by photoelectro-Fenton (PEF) process with in-situ H2O2 electrogeneration and UVA light irradiation has been envisaged for the removal of organic pollutants from water, showing a high performance for the decolorization and mineralization of Tartrazine (Acid Yellow 23) solutions. EC has a dual purpose as a coagulation and catalyst source step since it allows the formation of Fe(OH)n (n = 2 or 3) coagulant and Fe3+/Fe2+ ions. The influence of the anode material (Fe and Al), supporting electrolyte, pH and current during the individual EC on the abatement of color and total organic carbon (TOC) has been assessed. EC with Fe in 0.05 M NaCl yielded the best results. Next, various single electrochemical advanced oxidation processes (EAOPs) such as electro-oxidation (EO), electro-Fenton (EF) and PEF with a Pt or boron-doped diamond (BDD) anode and an air-diffusion cathode (ADE) have been tested. PEF with BDD/ADE yielded the quickest degradation among all the EAOPs in NaCl, due to the action of oxidants like active chlorine as well as •OH formed at the anode surface from H2O oxidation and in the bulk from UV-enhanced Fenton's reaction between cathodic H2O2 and added Fe2+. Therefore, the two-step EC (Fe/steel)/PEF (BDD/ADE) process was the best EC/EAOP combination. The EC treatment in 0.05 M NaCl at natural pH 6.3 and 200 mA, followed by PEF treatment of the supernatant at pH 3.0 and 200 mA, yielded the best conditions with a total decolorization in 15 min of EC and total mineralization in ca. 300 min of PEF. GC–MS analysis showed the formation of several benzenic by-products during the application of EC/PEF. Independent electrolyses revealed the ability of EC to accumulate soluble chlorobenzene derivatives, which can be completely destroyed in the PEF step under the action of the mixture of oxidants, particularly by successive hydroxylation via •OH largely promoted in the bulk by the Fe2+ ions generated in EC.
    Applied Catalysis B: Environmental. 01/2014; s 150–151:116–125.
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    ABSTRACT: Comparison of tannery wastewater treatment results of electrocoagulation (EC), electro-oxidation (EOx), electro-Fenton (EF) and photoelectro-Fenton (PEF) processes using two current densities was performed and employed no only to assess the best electrochemical approach but also to have elements to suggest a combined and cost effective process. In this way, iron plates were used as the anode and cathode in the EC tests. For the EOx process, a boron-doped diamond (BDD) thin-film electrode was used as the anode, and an iron plate was employed as the cathode. For the EF and PEF treatments, both electrodes were of BDD and H2O2 was produced by O2 reduction at the cathode surface. Electrolytic trials were carried out in stirred open tank reactors containing 250 mL of wastewater applying either 65 or 111 mA cm−2. In PEF trials, the wastewater was irradiated using a 6 W UVA light source. The characterization of the sludge generated in the EC process showed that it was not dangerous for the environment. Total Organic Carbon (TOC) removal values were larger at the highest density. Higher mineralization on the other hand, was found in EF and PEF when the concentration of Fe2+ was 3.0 instead 1.0 mM. Comparison of the methods revealed that their efficiency to remove the organic pollutant increased in the order EOx < EC ∼ EF < PEF after 180 min of electrolysis. Furthermore, the information obtained from the study, also allowed designing a combined strategy aimed to produce an effluent suitable for discharge. The combination of EC followed by PEF was also studied. The results showed that the EC/PEF treatment gave higher organic removal than EC and was more economic than PEF, being able to yield 90% TOC reduction of the tannery wastewater.
    Journal of Electroanalytical Chemistry. 01/2014; 713:62–69.
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    ABSTRACT: Here, solutions with 0.185 mM of the herbicide diuron of pH 3.0 have been treated by electrochemical advanced oxidation processes (EAOPs) like electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and UVA photoelectro-Fenton (PEF) or solar PEF (SPEF). Trials were performed in stirred tank reactors of 100 mL and in a recirculation flow plant of 2.5 L using a filter-press reactor with a Pt or boron-doped diamond (BDD) anode and an air-diffusion cathode for H2O2 electrogeneration. Oxidant hydroxyl radicals were formed from water oxidation at the anode and/or in the bulk from Fenton’s reaction between added Fe2+ and generated H2O2. In both systems, the relative oxidation ability of the EAOPs increased in the sequence EO-H2O2 < EF < PEF or SPEF. The two latter processes were more powerful due to the photolysis of intermediates by UV radiation. In the stirred tank reactor, the PEF treatment with BDD was the most potent method, yielding 93% mineralization after 360 min at 100 mA cm−2. In the flow plant, the SPEF process attained a maximum mineralization of 70% at 100 mA cm−2. Lower current densities slightly reduced the mineralization degree in SPEF, enhancing the current efficiency and dropping the energy consumption. The diuron decay always obeyed a pseudo-first-order kinetics, with a much greater apparent rate constant in EF and SPEF compared to EO-H2O2. Oxalic and oxamic acids were detected as final carboxylic acids. Ammonium and chloride ions were also released, the latter ion being partially converted into chlorate and perchlorate ions at the BDD surface.
    Chemosphere 01/2014; 109:49–55. · 3.14 Impact Factor
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    ABSTRACT: Here, the synergetic effect of coupling solar photoelectro-Fenton (SPEF) and solar heterogeneous photocatalysis (SPC) on the mineralization of 200mL of a 20mg L(-1) atrazine solution, prepared from the commercial herbicide Gesaprim, at pH 3.0 was studied. Uniform, homogeneous and adherent anatase-TiO2 films onto glass spheres of 5mm diameter were prepared by the sol-gel dip-coating method and used as catalyst for SPC. However, this procedure yielded a poor removal of the substrate because of the low oxidation ability of positive holes and OH formed at the catalyst surface to destroy it. Atrazine decay was improved using anodic oxidation (AO), electro-Fenton (EF), SPEF and coupled SPEF-SPC at 100mA. The electrolytic cell contained a boron-doped diamond (BDD) anode and H2O2 was generated at a BDD cathode fed with an air flow. The removal and mineralization of atrazine increased when more oxidizing agents were generated in the sequence AO<EF<SPEF<coupled SPEF-SPC. Organics were destroyed by OH formed from water oxidation at the BDD anode in AO, along with OH formed from Fenton's reaction between added Fe(2+) and generated H2O2 in EF. In SPEF, solar radiation produced higher amounts of OH induced from the photolysis of Fe(III) species and photodecomposed intermediates like Fe(III)-carboxylate complexes. The synergistic action of sunlight in the most potent coupled SPEF-SPC was ascribed to the additional quick removal of several intermediates with the oxidizing agents formed at the TiO2 surface. After 300min of this treatment, 80% mineralization, 9% mineralization current efficiency and 1.93kWhg(-1) TOC energy cost were obtained. The mineralization of atrazine was inhibited by the production of cyanuric acid, which was the main byproduct detected at the end of the coupled SPEF-SPC process.
    Chemosphere 11/2013; · 3.14 Impact Factor
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    ABSTRACT: The mineralization of sulfanilamide solutions at pH 3.0 was comparatively studied by electro-Fenton (EF) and solar photoelectro-Fenton (SPEF) using a 2.5L pre-pilot plant containing a Pt/air-diffusion cell coupled with a solar photoreactor. Organics were primordially oxidized by hydroxyl radical (OH) formed from Fenton's reaction between H2O2 generated at the cathode and added Fe(2+) and/or under the action of sunlight. A mineralization up to 94% was achieved using SPEF, whereas EF yielded much poorer degradation. The effect of current density and Fe(2+) and drug concentrations on the degradation rate, mineralization current efficiency and energy cost per unit DOC mass of EF and/or SPEF was examined. The sulfanilamide decay always followed a pseudo first-order kinetics, being more rapid in SPEF due to the additional generation of OH induced by sunlight on Fe(III) species. Catechol, resorcinol, hydroquinone and p-benzoquinone were identified as aromatic intermediates. The final solutions treated by EF contained Fe(III) complexes of maleic, fumaric, oxamic and mainly oxalic acids, which are hardly destroyed by OH. The quick photolysis of Fe(III)-oxalate complexes by sunlight explains the higher oxidation ability of SPEF. The N content of sulfanilamide was mainly mineralized as NH4(+) ion and in much lesser extent as NO3(-) ion, whereas most of its initial S was converted into SO4(2-) ion.
    Chemosphere 04/2013; · 3.14 Impact Factor
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    ABSTRACT: Solutions of methyl orange azo dye were degraded by electrochemical oxidation using a 3 L flow plant with a boron-doped diamond (BDD)/stainless steel cell operating at constant current density, ambient temperature and liquid flow rate of 12 L min−1. A 23 factorial design considering the applied current density, azo dye concentration and electrolysis time as variable independents was used to analyze the process by response surface methodology. LC–MS analysis revealed the formation of seven oxidation products from the cleavage of the NN group of the dye, followed by deamination, formation of a nitro group and/or desulfonation of the resulting aromatics.
    Journal of Industrial and Engineering Chemistry. 03/2013; 19(2):571–579.
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    ABSTRACT: The electrochemical incineration of omeprazole, a widely prescribed gastrointestinal drug which is detected in natural waters, has been studied in a phosphate buffer of pH 7.0 by anodic oxidation with electrogenerated H(2)O(2) (AO-H(2)O(2)) operating at constant current density (j). The experiments were carried out in a cell equipped with either a Pt or a boron-doped diamond (BDD) anode and an air-diffusion cathode to continuously produce H(2)O(2). In these systems, organics are mainly oxidized by hydroxyl radicals formed at the Pt or BDD surface from water oxidation. A partial total organic carbon (TOC) abatement close to 78% for omeprazole was achieved by AO-H(2)O(2) with a BDD anode after consumption of 18 Ah L(-1) at 100 mA cm(-2), whereas the alternative use of Pt did not allow mineralizing the drug. However, the drug was totally removed using both anodes, although it decayed more rapidly using BDD. In this latter system, increasing j accelerated the degradation process, but lowering the mineralization current efficiency. Greater drug content also enhanced the degradation rate with higher mineralization degree and current efficiency. The kinetics for omeprazole decay always followed a pseudo-first-order reaction and its rate constant increased with increasing j and with decreasing its concentration. Seven heteroaromatic intermediates and four hydroxylated derivatives were detected by LC-MS, while nine short-linear carboxylic acids were identified and quantified by ion-exclusion HPLC. These acids were largely accumulated using Pt and rapidly removed using BDD, thus explaining the partial mineralization of omeprazole achieved by AO-H(2)O(2) with the latter anode. The release of inorganic ions such as NO(3)(-), NH(4)(+) and SO(4)(2-) was followed by ionic chromatography. A plausible reaction sequence for omeprazole mineralization involving all intermediates detected is proposed.
    Water Research 01/2013; · 4.66 Impact Factor
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    ABSTRACT: Here, 100 mg L−1 of dissolved organic carbon of aromatics including chloromethoxyphenols were prepared by exposition of a mixture of guaiacol, syringol, and vanillin in 200 mM NaClO at pH 3.0 and 25 °C for 14 h and further degraded by electrochemical advanced oxidation processes (EAOPs) like anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), and photoelectro-Fenton (PEF). Electrolyses were performed with a cell containing either a Pt or boron-doped diamond (BDD) anode and an air-diffusion cathode at constant current density. Oxidants were hydroxyl radicals (•OH) formed at the anode surface from water oxidation and in the bulk from Fenton’s reaction between added Fe2+ and H2O2 generated at the cathode, as well as active chlorine species produced from the anodic oxidation of HClO. Oxychlorine ions like ClO3− using Pt and ClO3− + ClO4− using BDD were detected in the electrolyzed solutions. A poor mineralization was found using the Pt/air-diffusion cell, with increasing relative oxidation ability in the sequence AO-H2O2 < EF < PEF. In contrast, overall mineralization was achieved in all EAOPs using the BDD/air-diffusion cell due to the larger amounts of highly oxidizing •OH generated at BDD. For this latter system, the effect of UVA light, current density, and NaClO and/or Fe2+ concentration on the mineralization rate was examined. Up to 11 chloroderivatives of the parent molecules including four chlorophenols, six chloromethoxyphenols, and one chloromethoxynaphthalene were identified by GC–MS. The removal of these aromatics in AO-H2O2 with Pt or BDD was monitored by UV–vis spectrophotometry, HPLC, and GC–MS.
    Electrocatalysis. 01/2013;
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    ABSTRACT: The degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has been studied by electro-oxidation (EOx) and electro-Fenton/BDD (EF/BDD) using a 3-L pre-pilot plant with a BDD/BDD cell of 64 cm2 of electrode area. Electrolyses were performed with 60 mg L−1 2,4-D in 0.05 M Na2SO4 at pH 3.0, current densities between 7.8 and 31 mA cm−2, and liquid flow rates between 4 and 10 L min−1. In these electrochemical advanced oxidation processes, the main oxidants are hydroxyl radicals (•OH) formed from water oxidation at the BDD anode and/or from Fenton’s reaction between added Fe2+ and H2O2 generated at the BDD cathode. The EOx treatment at 31 mA cm−2 yielded 70 % mineralization as maximal at 160 min, which decreased at lower liquid flow rate because it was limited by the mass transport of organics toward the anode. Faster degradation was found for EF/BDD with 0.7 mM Fe2+, leading to 81–83 % of mineralization in 120 min. High current efficiency was determined at the beginning of this process, and the lowest energy cost of 95 kWh kg−1 TOC (2.0 kWh m−3) was obtained at 7.8 mA cm−2. 2,4-D was rapidly removed by EF/BDD. Four chloroaromatic products (2,4-dichlorophenol, 4,6-dichlororesorcinol, chlorohydroquinone, and chloro-p-benzoquinone) and three hydroxylated derivatives were detected by liquid chromatography–mass spectrometry, whereas hydroquinone and p-benzoquinone were identified by reversed-phase HPLC. A reaction sequence for the degradation of 2,4-D by EOx and EF/BDD involving all detected aromatics is proposed.
    Electrocatalysis. 01/2013;
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    ABSTRACT: The mechanism of the oxygen reduction reaction (ORR) on nanoparticulated Pt/C-Nafion electrodes prepared in one step has been studied to simulate the reaction in the cathode of a Polymer Electrolyte Fuel Cell (PEFC). The kinetic parameters have been obtained by hydrodynamic polarization in O2-saturated 0.01–1.00 M H2SO4 and temperatures in the range 25.0–50.0 °C. The ORR current density was maximum and practically independent of the ionomer fraction in the rage 10–55 wt% Nafion. The poorer proton conductivity for lower Nafion fractions and the formation of catalyst areas completely surrounded by Nafion together with adsorption of Pt sites by sulfonate groups for higher Nafion fractions, explain the minor ORR activity in these conditions. The ionomer influence on the O2 diffusion at high overpotentials for Pt/C-Nafion was negligible when the Nafion content was smaller than 20 wt%. The higher kinetic current density for Pt/C-Nafion (100 mA cm−2) with respect to smooth Pt-Nafion (40 mA cm−2), together with the smaller activation energy of the former (25 ± 4 kJ mol−1) with respect to the latter (42 ± 5 kJ mol−1) highlighted the better properties attained by the nanosize effect. A remarkable novel result is that the reaction order of H+ in HClO4 is close to unity, whereas in sulfuric acid it is significantly smaller and changes with potential, what has been related to the sulfate adsorption. The anomalous dependence of the charge transfer coefficient with temperature was then explained by the thermal change of the double layer structure and the variation of the coverage of adsorbed species on Pt. The more sensitive effect for Pt/C-Nafion than for smooth Pt-Nafion was ascribed to the stronger interaction between the components when the nanoparticles are involved.
    International Journal of Hydrogen Energy 12/2012; 37(23):17828–17836. · 3.55 Impact Factor
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    ABSTRACT: The modification of carbon-supported Pt nanoparticles, high performance (HP) 20% Pt on Vulcan XC-72 carbon black (Pt/C electrocatalyst), by spontaneous deposition of Ru species is examined employing electrochemical and structural techniques. Thin-layer electrodes were prepared by applying aqueous catalyst inks of Pt/C on glassy carbon (GC) disks. Ru deposition was carried out by immersion of the prepared electrode in deaerated RuCl3/HClO4 solutions. The subsequent cyclic voltammetry experiments of the modified electrocatalysts (Ru(Pt)/C) were performed in 0.5 M H2SO4 to determine the Ru coverage and the electroactive surface. CO stripping voltammetry showed the promotional effect of Ru(Pt)/C for the CO oxidation compared to Pt/C. The structural characterization of the modified electrocatalysts was performed by transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analyses, fast Fourier transform (FFT), selected-area electron diffraction (SAED), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). TEM observations revealed no appreciable signals of Ru agglomerates, and EDX confirmed the regular incorporation of Ru species to the nanoparticles. XRD analyses showed the characteristic profile of the Pt face-centered cubic (FCC) structure and the absence of crystalline Ru or Ru oxides. The application of the Williamson–Hall models indicated that Ru incorporation did not significantly affect the internal strain of the Pt nanoparticles, the increase of the crystallite size being attributed to an epitaxial growth of the Ru deposit. XPS measurements reported the presence of nonreducible RuO2 and hydrous RuO2 (RuOxHy) as the main Ru species in Ru(Pt)/C, the hydrous species justifying the promotional effect for the CO oxidation.
    The Journal of Physical Chemistry C. 08/2012; 116(34):18469–18478.

Publication Stats

2k Citations
430.88 Total Impact Points

Institutions

  • 1985–2014
    • University of Barcelona
      • • Department of Physical Chemistry
      • • Departament de Química Orgànica
      Barcino, Catalonia, Spain
  • 2013
    • Universidade Tiradentes
      • Institute for Technology and Research (ITP)
      Aracaju, Estado de Sergipe, Brazil
  • 2012
    • Universidade Federal de São Carlos
      • Departamento de Química (DQ)
      São Carlos, Estado de Sao Paulo, Brazil
  • 2010–2011
    • Polytechnic University of Catalonia
      Barcino, Catalonia, Spain
  • 2008
    • Università degli Studi di Genova
      • Department of Chemistry and Industrial Chemistry
      Genova, Liguria, Italy
    • University of Milan
      Milano, Lombardy, Italy
  • 2001–2004
    • University of Oviedo
      • Department of Organic and Inorganic Chemistry
      Oviedo, Asturias, Spain
  • 1984–1998
    • Autonomous University of Barcelona
      • Departamento de Química
      Cerdanyola del Vallès, Catalonia, Spain