Enric Brillas

University of Barcelona, Barcino, Catalonia, Spain

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Publications (272)927.7 Total impact

  • Abdoulaye Thiam, Ignasi Sirés, Enric Brillas
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    ABSTRACT: The degradation of 130 mL of mixtures of food azo dyes E122, E124 and E129 has been studied by electro-Fenton (EF) and UVA photoelectro-Fenton (PEF) using a stirred tank reactor with either a boron-doped diamond (BDD) or Pt anode and an air-diffusion cathode. The main oxidant was hydroxyl radical formed at the anode from water oxidation and in the bulk from Fenton's reaction between added Fe(2+) and H2O2 generated at the cathode. In sulfate medium, fast decolorization was found for all systems, but the almost total mineralization was more rapidly achieved by PEF with BDD. The performance with a real water matrix was slightly worse, although the removal of total organic load was still as high as 95%. The solar PEF (i.e., SPEF) treatment of dye mixtures using a 2.5 L flow plant with a BDD/air-diffusion cell coupled to a planar solar photoreactor is also reported. Fast decolorization and almost total mineralization was found in the presence of either sulfate, perchlorate, nitrate or a mixture of sulfate + chloride ions. In chloride medium, however, the formation of recalcitrant chloroderivatives decelerated the degradation process. Greater current efficiency and lower specific energy consumption were attained in sulfate medium at lower current density and higher azo dye content. A plausible reaction sequence based on 18 aromatic intermediates identified by GC-MS and 6 short-linear carboxylic acids detected by ion-exclusion HPLC has been proposed. The SPEF process promoted the photodegradation of Fe(III)-oxalate complexes and other undetected products. Sulfate and nitrate ions were always released to the medium. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Water Research 09/2015; 81. DOI:10.1016/j.watres.2015.05.057 · 5.32 Impact Factor
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    ABSTRACT: The occurrence of food color additives in waters is becoming a hot topic due to their potential health effects, especially on children. The treatment of Ponceau 4R solutions by electro-oxidation (EO) with or without H2O2 production, electro-Fenton (EF) and photoelectro-Fenton (PEF) using small undivided and divided batch cells with either Pt or BDD as the anode has been thoroughly studied. The electrolyses were performed in different electrolytes like Na2SO4, NaCl, NaNO3 and LiClO4 in order to elucidate the changes in reactivity. Depending on the anode, cathode, process and electrolyte, the azo dye could be degraded due to the single or combined action of: (i) direct cathodic reduction and/or anodic oxidation, (ii) •OH-mediated oxidation at the anode vicinity or in the solution bulk, and (iii) active chlorine-mediated oxidation. The presence of Cl− led to the fastest decolorization, whereas it became detrimental for total organic carbon abatement. The oxidation of Cl− to active chlorine (Cl2 and HClO) and oxychlorine anions (ClO3− and ClO4−) by direct charge transfer or by M(•OH) and •OH was investigated. Color removal was much slower in SO42−, ClO4− and NO3− media, although the latter was particularly beneficial in PEF and/or using BDD. Regarding the mineralization, PEF outperformed the other technologies. Similar trends were observed in SO42− and ClO4− media, being slightly favored in NO3−. In contrast, Cl− medium tended to be detrimental due to the formation of refractory chloroderivatives, the destruction of M(•OH) to form less oxidizing (oxy) chloro radicals, oxychlorine anions and active chlorine, and the reaction between HClO and H2O2. Experiments in divided cells demonstrated the very small contribution of cathodic reduction of the dye and its by-products. Linear sweep voltammetry revealed the direct oxidation of both, Ponceau 4R and Cl− on the anode surface.
    Electrochimica Acta 08/2015; 173:523-533. DOI:10.1016/j.electacta.2015.05.085 · 4.09 Impact Factor
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    ABSTRACT: The degradation of 100 mL of 0.245 mM of the antibiotic ciprofloxacin in 0.05 M Na2SO4 at pH 3.0 has been studied by electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF), UVA photoelectro-Fenton (PEF) and solar PEF (SPEF). Electrolyses were performed with a stirred tank reactor using either a boron-doped diamond (BDD) or Pt anode and an air-diffusion cathode. In EF, PEF and SPEF, ciprofloxacin was rapidly removed due to its oxidation with (•)OH formed from Fenton's reaction between added Fe(2+) and H2O2 generated at the cathode. The larger electrochemical incineration of the antibiotic was achieved by SPEF with BDD with 95% mineralization thanks to the additional attack by hydroxyl radicals formed from water oxidation at the BDD anode surface and the photolysis of final Fe(III)-oxalate and Fe(III)-oxamate species from sunlight. Up to 10 primary intermediates and 11 hydroxylated derivatives were identified by LC-MS, allowing the proposal of a reaction sequence for ciprofloxacin mineralization. A different behavior was found when the same antibiotic concentration was oxidized in a synthetic urine matrix with high urea content and a mixture of PO4(3-), SO4(2-) and Cl(-) ions. Since Fenton's reaction was inhibited in this medium, only EO and EO-H2O2 processes were useful for mineralization, being the organics mainly degraded by HClO formed from Cl(-) oxidation. The EO process with a BDD/stainless steel cell was found to be the most powerful treatment for the urine solution, yielding 96% ciprofloxacin removal and 98% mineralization after 360 min of electrolysis at optimum values of pH 3.0 and current density of 66.6 mA cm(-2). The evolution of released inorganic ions was followed by ion chromatography. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Water Research 06/2015; 83:31-41. DOI:10.1016/j.watres.2015.05.066 · 5.32 Impact Factor
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    ABSTRACT: The decolorization and mineralization of solutions containing 230mgL(-1) of the food azo dye Allura Red AC at pH 3.0 have been studied upon treatment by electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF). Experiments were performed with a stirred tank reactor containing a boron-doped diamond (BDD) or Pt anode and an air-diffusion cathode to generate H2O2. The main oxidants were hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between H2O2 and added Fe(2+). The oxidation ability increased in the sequence EO-H2O2<EF<PEF and faster degradation was always obtained using BDD. PEF process with BDD yielded almost total mineralization following similar trends in SO4(2-), ClO4(-) and NO3(-) media, whereas in Cl(-) medium, mineralization was inhibited by the formation of recalcitrant chloroderivatives. GC-MS analysis confirmed the cleavage of the NN bond with formation of two main aromatics in SO4(2-) medium and three chloroaromatics in Cl(-) solutions. The effective oxidation of final oxalic and oxamic acids by BDD along with the photolysis of Fe(III)-oxalate species by UVA light accounted for the superiority of PEF with BDD. NH4(+), NO3(-) and SO4(2-) ions were released during the mineralization. Copyright © 2015 Elsevier B.V. All rights reserved.
    Journal of Hazardous Materials 06/2015; 290. DOI:10.1016/j.jhazmat.2015.02.050 · 4.33 Impact Factor
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    ABSTRACT: A solution with 0.245 mM of the diazo dye Evans Blue and 0.50 mM Fe2+ as catalyst of pH 3.0 was comparatively degraded by electrochemical processes based on Fenton’s reaction chemistry like electro-Fenton (EF), photoelectro-Fenton (PEF) with a 6 W UVA light and solar photoelectro-Fenton (SPEF). Electrolytic trials were made in a 100 mL stirred tank reactor with a boron-doped diamond (BDD) anode and an air-diffusion cathode at constant current density. Organics were destroyed by OH produced at the anode surface from water oxidation and in the bulk from Fenton’s reaction between added Fe2+ and H2O2 generated at the cathode. Evans Blue decay obeyed a pseudo-first-order kinetics and was much faster than solution decolorization due to the formation of colored aromatic products. The mineralization rate rose in the sequence EF < PEF < SPEF. Almost total mineralization was rapidly achieved in SPEF at current density ⩾66.7 mA cm−2 because of the potent UV radiation from sunlight. Up to 19 aromatic intermediates and 16 hydroxylated derivatives including diazo, monoazo, biphenylic, benzenic, naphthalenic and phthalic acid compounds were detected by LC–MS. The SPEF process was performed in a 10 L flow plant with a Pt/air-diffusion cell coupled to a CPC photoreactor in order to confirm its viability at industrial scale. 88% mineralization with 42% current efficiency and 2.13 kWh kg−1 DOC energy consumption were obtained after 300 min of treatment at 55.4 mA cm−2. Nine short-linear carboxylic acids were identified as final products, oxalic, formic and oxamic acids being the most persistent. The photodecarboxylation of Fe(III)–carboxylate complexes explained the good oxidation ability of PEF and SPEF. The initial S of the diazo dye was transformed into SO42− ion, whereas its initial N was mineralized to NO3− ion but largely lost as N-volatile products.
    Journal of electroanalytical chemistry 06/2015; 747. DOI:10.1016/j.jelechem.2015.03.032 · 2.87 Impact Factor
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    ABSTRACT: The degradation of solutions with 0.260 mM of the diazo dye Congo Red at pH 3.0 has been studied by electrochemical advanced oxidation processes (EAOPs) like anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) with a 6 W UVA light. Experiments were made in a 100 mL stirred tank reactor with a boron-doped diamond (BDD) anode and an air-diffusion cathode at constant current density (j). In these systems, organics were mainly destroyed by OH formed at the anode surface from water oxidation and/or in the bulk from Fenton’s reaction between added Fe2+ and cathodically generated H2O2. The oxidation power of the EAOPs increased in the sequence AO- H2O2 < EF < PEF. Almost total mineralization was attained after 360 min of PEF at j ≥ 66.7 mA cm−2 due to the parallel photolytic action of UVA light. In all the EAOPs, increasing j enhanced the degradation process, but with a loss of mineralization current efficiency and higher energy consumption. Congo Red decay always obeyed a pseudo-first-order kinetics. The study of the Congo Red degradation in a 2.5 L solar flow plant with a Pt/air-diffusion cell confirmed the viability of the solar PEF (SPEF) treatment at industrial scale. Optimum conditions were found for 0.260 mM of Congo Red with 0.50 mM Fe2+ at 100 mA cm−2, yielding almost total mineralization in 240 min with about 49% current efficiency and 0.45 kWh (g DOC)−1 energy consumption. LC-MS analysis of treated solutions allowed the identification of 21 aromatic intermediates and 13 hydroxylated derivatives, including diazo, monoazo, biphenyl, benzene, naphthalene and phthalic acid compounds. Tartatic, tartronic, acetic, oxalic and oxamic acids were detected as final carboxylic acids in all the EAOPs. The fast photodecarboxylation of the Fe(III)-carboxylate complexes explained the higher oxidation ability of the photo-assisted methods of PEF and SPEF. The initial N of the dye was mainly lost as N-volatile products and mineralized to NO3− ion and in lesser extent to NH4+ ion, whereas its initial S was converted into SO42− ion.
    Applied Catalysis B Environmental 06/2015; 168-169:559-571. DOI:10.1016/j.apcatb.2015.01.019 · 6.01 Impact Factor
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    ABSTRACT: Here, 2.5 L of solutions of the pharmaceutical ranitidine (RNTD) at pH 3.0 have been comparatively degraded by electro-Fenton (EF) and solar photoelectro-Fenton (SPEF) processes using a pre-pilot flow plant with a Pt/air-diffusion cell. RNTD was oxidized by hydroxyl radicals coming from water oxidation at the Pt anode and Fenton’s reaction between added Fe2+ and H2O2 generated at the air-diffusion cathode. In SPEF, the cell was coupled to a flat solar photoreactor to irradiate the solution with sunlight. The potent combined action of hydroxyl radicals and photolysis by sunlight explains the higher oxidation ability of SPEF compared to EF, attaining 80% mineralization as maximal. The optimum Fe2+ content as catalyst was 0.50 mM. The effect of current density and drug concentration on the degradation rate of RNTD, mineralization current efficiency and energy consumption for EF and SPEF was examined. The RNTD decay always followed a pseudo-first-order kinetics, having a greater oxidation rate for SPEF by the additional generation of hydroxyl radicals induced by photolysis of Fe(III) species. Malic, pyruvic, acetic, oxalic, oxamic and formic acids were detected as final carboxylic acids. The three latter acids were the main components of the final treated solution in EF because their Fe(III) complexes were not destroyed by generated hydroxyl radicals. The quick photolysis of such Fe(III)-carboxylate species by sunlight explains the greater oxidation power of SPEF. The initial S atom of RNTD was released as sulfate ion, whereas its initial N atoms were converted into ammonium ion along with a smaller proportion of nitrate ion.
    Separation and Purification Technology 05/2015; 146. DOI:10.1016/j.seppur.2015.03.046 · 3.07 Impact Factor
  • Enric Brillas, Ignasi Sirés
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    ABSTRACT: Electrochemical technology has attracted increasing interest in recent years as an environment-friendly solution to many industrial problems and challenges. First, we give an overview on the fundamentals of electrochemical processes for the removal of pharmaceuticals from water, particularly electrochemical oxidation and Fenton-based processes, such as electro-Fenton, and ultraviolet (UV) and solar photoelectro-Fenton, that have improved performance. We also mention other less studied methods, although the main focus is on reactivity elucidation by chromatography with UV or conductivity detection, especially by mass spectrometry techniques (e.g., coupled to gas chromatography or liquid chromatography), in order to discuss the degradation pathways of pharmaceuticals on the basis of the reactive species electrogenerated in each technology. In some cases, simultaneous assessment of toxicity adds crucial information for the future integration of these technologies in water-treatment facilities where pharmaceuticals and their byproducts can occur.
    TrAC Trends in Analytical Chemistry 05/2015; DOI:10.1016/j.trac.2015.01.013 · 6.61 Impact Factor
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    ABSTRACT: The current study has proved the technical feasibility of including electrochemical advanced oxidation processes (EAOPs) in a multistage strategy for the remediation of a sanitary landfill leachate that embraced: (i) first biological treatment to remove the biodegradable organic fraction, oxidize ammonium and reduce alkalinity, (ii) coagulation of the bio-treated leachate to precipitate humic acids and particles, followed by separation of the clarified effluent, and (iii) oxidation of the resulting effluent by an EAOP to degrade the recalcitrant organic matter and increase its biodegradability so that a second biological process for removal of biodegradable organics and nitrogen content could be applied. The influence of current density on an UVA photoelectro-Fenton (PEF) process was firstly assessed. The oxidation ability of various EAOPs such as electro-Fenton (EF) with two distinct initial total dissolved iron concentrations ([TDI]0), PEF and solar PEF (SPEF) was further evaluated and these processes were compared with their analogous chemical ones. A detailed assessment of the two first treatment stages was made and the biodegradability enhancement during the SPEF process was determined by a Zahn-Wellens test to define the ideal organics oxidation state to stop the EAOP and apply the second biological treatment. The best current density was 200 mA cm-2 for a PEF process using a BDD anode, [TDI]0 of 60 mg L-1, pH 2.8 and 20 °C. The relative oxidation ability of EAOPs increased in the order EF with 12 mg [TDI]0 L-1 < EF with 60 mg [TDI]0 L-1 < PEF with 60 mg [TDI]0 L-1 ≤ SPEF with 60 mg [TDI]0 L-1, using the abovementioned conditions. While EF process was much superior to the Fenton one, the superiority of PEF over photo-Fenton was less evident and SPEF attained similar degradation to solar photo-Fenton. To provide a final dissolved organic carbon (DOC) of 163 mg L-1 to fulfill the discharge limits into the environment after a second biological process, 6.2 kJ L-1 UV energy and 36 kWh m-3 electrical energy were consumed using SPEF with a BDD anode at 200 mA cm-2, 60 mg [TDI]0 L-1, pH 2.8 and 20 °C.
    Water Research 05/2015; DOI:10.1016/j.watres.2015.05.036 · 5.32 Impact Factor
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    Carlos A Martinez-Huitle, Enric Brillas
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    ABSTRACT: As the environment preservation gradually becomes a matter of major social concern and more strict legislation is being imposed on effluent discharge, more effective processes are required to deal with non-readily biodegradable and toxic pollutants. Synthetic organic dyes in industrial effluents cannot be destroyed in conventional wastewater treatment and consequently, an urgent challenge is the development of new environmentally benign technologies able to mineralize completely these non-biodegradable compounds. This review aims to increase the knowledge on the electrochemical methods used at lab and pilot plant scale to decontaminate synthetic and real effluents containing dyes, considering the period from 2009 to 2013, as an update of our previous review up to 2008. Fundamentals and main applications of electrochemical advanced oxidation processes and the other electrochemical approaches are described. Typical methods such as electrocoagulation, electrochemical reduction, electrochemical oxidation and indirect electro-oxidation with active chlorine species are discussed. Recent advances on electrocatalysis related to the nature of anode material to generate strong heterogeneous radical dotOH as mediated oxidant of dyes in electrochemical oxidation are extensively examined. The fast destruction of dyestuffs mediated with electrogenerated active chlorine is analyzed. Electro-Fenton and photo-assisted electrochemical methods like photoelectrocatalysis and photoelectro-Fenton, which destroy dyes by heterogeneous radical dotOH and/or homogeneous radical dotOH produced in the solution bulk, are described. Current advantages of the exposition of effluents to sunlight in the emerging photo-assisted procedures of solar photoelectrocatalysis and solar photoelectro-Fenton are detailed. The characteristics of novel combined methods involving photocatalysis, adsorption, nanofiltration, microwaves and ultrasounds among others and the use of microbial fuel cells are finally discussed.
    Applied Catalysis B: Environmental 05/2015; 166-167:603. DOI:10.1016/j.apcatb.2014.11.016 · 5.63 Impact Factor
  • 04/2015; 5(2):815-837. DOI:10.3390/catal5020815
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    ABSTRACT: The degradation of 2.5L of Allura Red AC solutions in sulfate medium containing 0.50mM Fe(2+) has been studied by solar photoelectro-Fenton (SPEF) using a flow plant equipped with a Pt/air-diffusion cell and a solar photoreactor. Comparative electro-Fenton treatment yielded rapid total decolorization but poor mineralization, since most products were slowly destroyed by OH formed from Fenton's reaction between Fe(2+) and H2O2 generated at the air-diffusion cathode. In contrast, the potent action of UV radiation from sunlight in SPEF allowed the rapid photolysis of recalcitrant intermediates, thus giving rise to a quick mineralization. Sulfate and nitrate ions, along with a large proportion of volatile N-derivatives, were always released. The increase in current density and decrease in azo dye concentration accelerated the decolorization and mineralization in SPEF, although lower current efficiency and greater specific energy consumption were obtained. The most cost-effective SPEF treatment was found for 460mgL(-1) azo dye in 0.05M Na2SO4 at 50mAcm(-2), which yielded 95% mineralization with 81% current efficiency and 8.50kWhm(-3). No significant effect of sulfate concentration was found. Up to 16 aromatic intermediates and 11 short-chain carboxylic acids, including oxalic and oxamic as the most persistent ones, were detected by GC-MS and HPLC. The large oxidation ability of SPEF can be explained by the quick photolysis of Fe(III)-oxalate complexes and other undetected intermediates. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Chemosphere 04/2015; 136:1-8. DOI:10.1016/j.chemosphere.2015.03.047 · 3.50 Impact Factor
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    ABSTRACT: The degradation of 10 dm3 of solutions of the heterocyclic antibiotic metronidazole in 0.10 mol dm−3 Na2SO4 of pH 3.0 has been comparatively studied by electro-Fenton (EF) and solar photoelectro-Fenton (SPEF). Experiments were performed in a solar flow plant equipped with a Pt/air-diffusion cell and coupled to a compound parabolic collector (CPC) photoreactor. A very weak mineralization was found for the EF process in the dark, indicating a large recalcitrance of heterocyclic compounds to be destroyed by hydroxyl radicals formed at the Pt anode from water oxidation and mainly in the bulk from Fenton's reaction between added Fe2+ and cathodically generated H2O2. The quick photolysis of intermediates by UV radiation from sunlight enhanced largely the mineralization process by SPEF. The effect of applied current density and Fe2+ and drug contents on the SPEF treatment was examined. The best process was found for 1.39 mmol dm−3 metronidazole with 0.50 mmol dm−3 Fe2+ at 55.4 mA cm−2 giving 53% mineralization, 36% mineralization current efficiency and 0.339 kWh (g DOC)−1 in 300 min. Metrodinazole was completely removed and its decay obeyed a pseudo-first-order kinetics. LC-MS analysis allowed identifying five heterocyclic products and twelve hydroxylated derivatives. Ion-exclusion HPLC analysis revealed that final oxalic and oxamic acids were practically removed at the end of electrolysis due to the efficient photolysis of their Fe(III) complexes by sunlight. The initial N of metronidazole gave NO3− ion as main inorganic ion. A large proportion of initial N remained in solution as unidentified N-products and their major part was lost as N-volatile species. Based on the detected products, a reaction sequence for metronidazole mineralization by SPEF is proposed.
    Electrochimica Acta 03/2015; 165. DOI:10.1016/j.electacta.2015.02.243 · 4.09 Impact Factor
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    ABSTRACT: Apart from a high biodegradable fraction consisting of organic acids, sugars and alcohols, winery wastewaters exhibit a recalcitrant fraction containing high-molecular-weight compounds as polyphenols, tannins and lignins. In this context, a winery wastewater was firstly subjected to a biological oxidation to mineralize the biodegradable fraction and afterwards an electrochemical advanced oxidation process (EAOP) was applied in order to mineralize the refractory molecules or transform them into simpler ones that can be further biodegraded. The biological oxidation led to above 97% removals of dissolved organic carbon (DOC), chemical oxygen demand (COD) and 5-day biochemical oxygen demand (BOD5), but was inefficient on the degradation of a bioresistant fraction corresponding to 130 mg L(-1) of DOC, 380 mg O2 L(-1) of COD and 8.2 mg caffeic acid equivalent L(-1) of total dissolved polyphenols. Various EAOPs such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), UVA photoelectro-Fenton (PEF) and solar PEF (SPEF) were then applied to the recalcitrant effluent fraction using a 2.2 L lab-scale flow plant containing an electrochemical cell equipped with a boron-doped diamond (BDD) anode and a carbon-PTFE air-diffusion cathode and coupled to a photoreactor with compound parabolic collectors (CPCs). The influence of initial Fe(2+) concentration and current density on the PEF process was evaluated. The relative oxidative ability of EAOPs increased in the order AO-H2O2 < EF < PEF ≤ SPEF. The SPEF process using an initial Fe(2+) concentration of 35 mg L(-1), current density of 25 mA cm(-2), pH of 2.8 and 25 °C reached removals of 86% on DOC and 68% on COD after 240 min, regarding the biologically treated effluent, along with energy consumptions of 45 kWh (kg DOC)(-1) and 5.1 kWh m(-3). After this coupled treatment, color, odor, COD, BOD5, NH4(+), NO3(-) and SO4(2-) parameters complied with the legislation targets and, in addition, a total dissolved polyphenols content of 0.35 mg caffeic acid equivalent L(-1) was found. Respirometry tests revealed low biodegradability enhancement along the SPEF process. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Water Research 02/2015; 75:95-108. DOI:10.1016/j.watres.2015.02.029 · 5.32 Impact Factor
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    ABSTRACT: Tyrosol (TY) is one of the most abundant phenolic components of olive oil mill wastewaters. Here, the degradation of synthetic aqueous solutions of 0.30 mM TY was studied by a novel heterogeneous electro-Fenton (EF) process, so-called EF-pyrite, in which pyrite powder was the source of Fe(2+) catalyst instead of a soluble iron salt used in classical EF. Experiments were performed with a cell equipped with a boron-doped diamond anode and a carbon-felt cathode, where TY and its products were destroyed by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between Fe(2+) and H2O2 generated at the cathode. Addition of 1.0 g L(-1) pyrite provided an easily adjustable pH to 3.0 and an appropriate 0.20 mM Fe(2+) to optimize the EF-pyrite treatment. The effect of current on mineralization rate, mineralization current efficiency and specific energy consumption was examined under comparable EF and EF-pyrite conditions. The performance of EF-pyrite was 8.6% superior at 50 mA due to self-regulation of soluble Fe(2+) by pyrite. The TY decay in this process followed a pseudo-first-order kinetics. The absolute rate constant for TY hydroxylation was 3.57 × 10(9) M(-1) s(-1), as determined by the competition kinetics method. Aromatic products like 3,4-dihydroxyphenylethanol, 4-hydroxyphenylacetic acid, 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid and catechol, as well as o-benzoquinone, were identified by GC-MS and reversed-phase HPLC. Short-chain aliphatic carboxylic acids like maleic, glycolic, acetic, oxalic and formic were quantified by ion-exclusion HPLC. Oxalic acid was the major and most persistent product found. Based on detected intermediates, a plausible mineralization pathway for TY by EF-pyrite was proposed. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Water Research 02/2015; 74C:77-87. DOI:10.1016/j.watres.2015.02.006 · 5.32 Impact Factor
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    ABSTRACT: A UVA photoelectro-Fenton (PEF) process mediated by Fe(III)–carboxylate complexes was applied to the removal of trimethoprim (TMP) antibiotic from water using a 2.2 L lab-scale flow plant equipped with a double compound parabolic collector (CPC) and an electrochemical cell composed of a boron-doped diamond (BDD) anode and a carbon–PTFE air-diffusion cathode. The presence of Fe(III)–carboxylate complexes enhances the regeneration of Fe3+ to Fe2+, allows to maintain iron in solution at higher pH values and can decrease the formation of Fe(III)–sulfate, Fe(III)–chloride and some Fe(III)–pollutants complexes. First, the efficiency of different carboxylate ligands like oxalate, citrate, tartrate and malate was assessed, followed by the application of various initial Fe(III)-to-carboxylate molar ratios and pH values. The PEF process with Fe(III)–oxalate, Fe(III)–citrate and Fe(III)–tartrate complexes revealed similar ability to degrade the antibiotic solution with the employment of 1:3, 1:1 and 1:1 Fe(III)-to-carboxylate molar ratios, respectively, and using pH of 4.5, Fe3+ concentration of 2.0 mg L−1 (total iron emission limit for the discharge of treated effluents according to the Portuguese legislation), current density of 5 mA cm−2 and 20 °C. The PEF process mediated by Fe(III)–malate complexes was much less effective. 1:6 and 1:9 Fe(III)-to-oxalate molar ratios were required to yield similar TMP removal kinetics at pH 5.0 and 5.5 compared to pH 4.5, respectively. Additionally, the influence of initial TMP content and solution temperature on the PEF process with Fe(III)–carboxylate complexes was assessed and the role of the different reactive oxidizing species was clarified by the addition of scavenging agents. Generated low-molecular-weight carboxylic acids were monitored by ion-exclusion HPLC.
    Applied Catalysis B Environmental 01/2015; 162:34–44. DOI:10.1016/j.apcatb.2014.06.008 · 6.01 Impact Factor
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    ABSTRACT: Solutions of 2.5 L with 209.3 mg L À1 of the azo dye Carmoisine in 0.050 M SO 4 2À , ClO 4 À or Cl À have been comparatively treated by electrochemical oxidation with electrogenerated H 2 O 2 (EO-H 2 O 2) and electro-Fenton (EF) with 0.5 mM Fe 2+ as catalyst at constant current density. Experiments were made using a recirculation flow plant containing a reactor with a boron-doped diamond (BDD) anode and an air-diffusion cathode to allow H 2 O 2 generation. The dye and its oxidation products were oxidized by hydroxyl radical and/or HClO formed at the anode from water or Cl À oxidation, respectively, in EO-H 2 O 2 , as well as by hydroxyl radical produced in the bulk from Fenton's reaction between added Fe 2+ and generated H 2 O 2 in EF. In both methods, the decolorization process was always much faster in Cl À medium because of the quick oxidation of colored compounds by HClO, being enhanced by increasing current density and Cl À concentration. The solutions with SO 4 2À or ClO 4 À were more rapidly decolorized in EF due to the higher oxidation power of hydroxyl radicals in the bulk. Regarding the overall decontamination, a poor and similar mineralization of about 50% was obtained by EO-H 2 O 2 at 480 min in all the supporting electrolytes at 100 mA cm À2. The comparative EF treatments were always much more powerful, being SO 4 2À the most favorable medium leading to 76% mineralization with the lowest energy consumption. Up to 15 aromatic products were detected by GC–MS and short-linear carboxylic acids like tartronic, oxalic, oxamic and for-mic were quantified by ion-exclusion HPLC. The large persistence of Fe(III)-oxalate complexes accounted for the partial mineralization of the Carmoisine solution in EF. Nitrate and sulfate were the major ions released during the mineralization process.
    Separation and Purification Technology 01/2015; 140(2015):43-52. DOI:10.1016/j.seppur.2014.11.012 · 3.07 Impact Factor
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    ABSTRACT: The degradation of 20.0 mg L−1 of trimethoprim (TMP), an antibiotic commonly detected in wastewaters, in an aqueous solution with 7.0 g L−1 Na2SO4 was accomplished by electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), photoelectro-Fenton (PEF) and solar photoelectro-Fenton (SPEF), as well as by the classical Fenton and photo-Fenton processes. All experiments were performed in a novel 2.2 L lab-scale flow plant equipped with compound parabolic collectors (CPCs) and an electrochemical filter-press cell with a BDD or Pt anode and a carbon-PTFE air-diffusion cathode to electrogenerate H2O2. The effect of initial Fe2+ concentration, current density and pH on the PEF method with the BDD anode (PEF-BDD) was firstly assessed by means of TMP and dissolved organic carbon (DOC) decays, aiming to establish a treatment process using minimal iron concentration, adequate current density/H2O2 production and maximal pH. This treatment was efficiently performed using a low Fe2+ dose of 2.0 mg L−1, a low current density of 5 mA cm−2 and pH of 3.5 without iron precipitation. The relative oxidation ability of EAOPs using the BDD/air-diffusion cell increased in the order: AO-H2O2 < EF < PEF < SPEF. The EF-BDD and PEF-BDD processes were more effective than the comparable Fenton and photo-Fenton ones. The PEF-BDD process exhibited slightly faster TMP degradation than the PEF-Pt one, whereas in SPEF the influence of the anode was almost negligible. After ca. 37 kJ L−1 UV energy, 77 and 73% mineralization with 30 and 26% current efficiency and 1.2 and 0.9 kWh m−3 energy cost were obtained, respectively. It was found a slow and partial TMP mineralization mainly linked to the formation of a high content of hardly oxidizable N-derivatives, containing the major part of N. Up to 18 aromatic products and 19 hydroxylated derivatives were detected by LC-MS during TMP degradation by PEF-Pt. An additional SPEF-Pt experiment using a real wastewater matrix spiked with TMP attained slower TMP and DOC decays.
    Applied Catalysis B Environmental 11/2014; 160-161:492-505. DOI:10.1016/j.apcatb.2014.05.052 · 6.01 Impact Factor
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    ABSTRACT: Ranitidine (RNTD) is a widely prescribed histamine H2-receptor antagonist whose unambiguous presence in water sources appointed it as an emerging pollutant. Here, the degradation of 0.1mM of this drug in aqueous medium was studied by electrochemical advanced oxidation processes (EAOPs) like anodic oxidation with electrogenerated H2O2 and electro-Fenton using Pt/carbon-felt, BDD/carbon-felt and DSA-Ti/RuO2-IrO2/carbon-felt cells. The higher oxidation power of the electro-Fenton process using a BDD anode was demonstrated. The oxidative degradation of RNTD by the electrochemically generated OH radicals obeyed a pseudo-first order kinetics. The absolute rate constant for its hydroxylation reaction was 3.39×10(9)M(-1)s(-1) as determined by the competition kinetics method. Almost complete mineralization of the RNTN solution was reached by using a BDD anode in both anodic oxidation with electrogenerated H2O2 and electro-Fenton processes. Up to 11cyclic intermediates with furan moiety were detected from the degradation of RNTD, which were afterwards oxidized to short-chain carboxylic acids before their mineralization to CO2 and inorganic ions such as NH4(+), NO3(-) and SO4(2-). Based on identified products, a plausible reaction pathway was proposed for RNTD mineralization. Toxicity assessment by the Microtox® method revealed that some cyclic intermediates are more toxic than the parent molecule. Toxicity was quickly removed following the almost total mineralization of the treated solution. Overall results confirm the effectiveness of EAOPs for the efficient removal of RNTD and its oxidation by-products from water. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Chemosphere 10/2014; 117C:644-651. DOI:10.1016/j.chemosphere.2014.09.084 · 3.50 Impact Factor
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    ABSTRACT: Electrochemical advanced oxidation processes (EAOPs) have been widely investigated as promising technologies to remove trace organic contaminants from water, but have rarely been used for the treatment of real waste streams. Anodic oxidation with a boron-doped diamond (BDD) anode was applied for the treatment of secondary effluent from a municipal sewage treatment plant containing 29 target pharmaceuticals and pesticides. The effectiveness of the treatment was assessed from the contaminants decay, dissolved organic carbon and chemical oxygen demand removal. The effect of applied current and pH was evaluated. Almost complete mineralization of effluent organic matter and trace contaminants can be obtained by this EAOP primarily due to the action of hydroxyl radicals formed at the BDD surface. The oxidation of Cl(-) ions present in the wastewater at the BDD anode gave rise to active chlorine species (Cl2/HClO/ClO(-)), which are competitive oxidizing agents yielding chloramines and organohalogen byproducts, quantified as adsorbable organic halogen. However, further anodic oxidation of HClO/ClO(-) species led to the production of ClO3(-) and ClO4(-) ions. The formation of these species hampers the application as a single-stage tertiary treatment, but posterior cathodic reduction of chlorate and perchlorate species may reduce the risks associated to their presence in the environment. Copyright © 2014 Elsevier B.V. All rights reserved.
    Journal of Hazardous Materials 10/2014; 283. DOI:10.1016/j.jhazmat.2014.10.003 · 4.33 Impact Factor

Publication Stats

7k Citations
927.70 Total Impact Points

Institutions

  • 1985–2015
    • University of Barcelona
      • • Department of Physical Chemistry
      • • Departament de Química Orgànica
      Barcino, Catalonia, Spain
  • 2011
    • Universidade Federal do Rio Grande do Norte
      • Departamento de Química
      Natal, Rio Grande do Norte, Brazil
  • 2001–2004
    • University of Oviedo
      • Department of Organic and Inorganic Chemistry
      Oviedo, Asturias, Spain
  • 2002–2003
    • Cheikh Anta Diop University, Dakar
      Dakar, Dakar, Senegal
  • 1986
    • University of Cordoba (Spain)
      Cordoue, Andalusia, Spain
  • 1984
    • Autonomous University of Barcelona
      Cerdanyola del Vallès, Catalonia, Spain