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Here, we comprehensively investigated methanol electrooxidation on Cu-based catalysts, allowing us to build the first microfluidic fuel cell (µFC) equipped with a Cu anode and a metal-free cathode that converts energy from methanol. We applied a simple, fast, small-scale, and surfactant-free strategy for synthesizing Cu-based nanoparticles at room temperature in steady state (ST), under mechanical stirring (MS), or under ultrasonication (US). The morphology evaluation of the Cu-based samples reveals that they have the same nanoparticle (NP) needle-like form. The elemental mapping composition spectra revealed that pure Cu or Cu oxides were obtained for all synthesized materials. In addition to having more Cu2O on the surface, sample US had more Cu(OH)2 than the others, according to X-ray diffractograms and X-ray photoelectron spectroscopy. The sample US is less carbon-contaminated because of the local heating of the sonic bath, which also enhances the cleanliness of the Cu surface. The activity of the Cu NPs was investigated for methanol electrooxidation in an alkaline medium through electrochemical and spectroelectrochemical measurements. The potentiodynamic and potentiostatic experiments showed higher current densities for the NPs synthesized in the US. In situ FTIR experiments revealed that the three synthesized NP materials eletcrooxidize methanol completely to carbonate through formate. Most importantly, all pathways were led without detectable CO, a poisoning molecule not found at high overpotentials. The reaction path using the US electrode experienced an additional round of formate formation and conversion into carbonate (or CO2 in the thin layer) after 1.0 V (vs. Ag/Ag/Cl), suggesting improved catalysis. The high activity of NPs synthesized in the US is attributed to effective dissociative adsorption of the fuel due to the site's availability and the presence of hydroxyl groups that may fasten the oxidation of adsorbates from the surface. After understanding the surface reaction, we built a mixed-media µFC fed by methanol in alkaline medium and sodium persulfate in acidic medium. The µFC was equipped with Cu NPs synthesized in ultrasonic-bath-modified carbon paper as the anode and metal-free carbon paper as the cathode. Since the onset potential for methanol electrooxidation was 0.45 V and the reduction reaction revealed 0.90 V, the theoretical OCV is 0.45 V, which provides a spontaneous coupled redox reaction to produce power. The µFC displayed 0.56 mA cm-2 of maximum current density and 26 µW cm-2 of peak power density at 100 µL min-1. This membraneless system optimizes each half-cell individually, making it possible to build fuel cells with noble metal-free anodes and metal-free cathodes.

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This study unveils a novel role of bare graphite as a catalyst in glycerol electrooxidation and hydrogen evolution reactions, challenging the prevailing notion that current collectors employed in electrolyzers are inert. Half-cell experiments elucidate the feasibility of glycerol oxidation and hydrogen production on bulk graphite electrodes at potentials exceeding 1.7 V. The investigation of varying glycerol concentrations (0.05 to 1.5 mol L-1) highlights a concentration-dependent competition between glycerol electrooxidation and oxygen evolution reactions. Employing an H-type glycerol electrolyzer, polarization curves reveal significant activation polarization attributed to the low electroactivity of the anode. Glycerol electrolysis at different concentrations yields diverse product mixtures, including formate, glycolate, glycerate, and lactate at the anode, with concurrent hydrogen generation at the cathode. The anolyte composition changes with glycerol concentration, resulting in less-oxidized compounds at higher concentrations and more oxidized compounds at lower concentrations. The cell voltage also influences the product formation selectivity, with an increased voltage favoring more oxidized compounds. The glycerol concentration also affects hydrogen production, with lower concentrations yielding higher hydrogen amounts, peaking at 3.5 V for 0.05 mol L-1. This model quantitatively illustrates graphite's contribution to current and product generation in glycerol electrolyzers, emphasizing the significance of background current and products originating from current collectors if in contact with the reactants. These results have an impact on the efficiency of the electrolyzer and raise questions regarding possible extra non-noble "nonparticipating" current collectors that could affect overall performance. This research expands our understanding of electrocatalysis on graphite surfaces with potential applications in optimizing electrolyzer configurations for enhanced efficiency and product selectivity.

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Fuel cell technology has developed due to diminishing dependence on fossil fuels and carbon footprint production. This work focuses on a nickel-aluminum bronze alloy as an anode produced by additive manufacturing as bulk and porous samples, studying the effect of designed porosity and thermal treatment on mechanical and chemical stability in molten carbonate (Li2CO3-K2CO3). Micrographs showed a typical morphology of the martensite phase for all samples in as-built conditions and a spheroid structure on the surface after the heat treatment, possibly revealing the formation of molten salt deposits and corrosion products. FE-SEM analysis of the bulk samples showed some pores with a diameter near 2-5 µm in the as-built condition, which varied between 100 and -1000 µm for the porous samples. After exposure, the cross-section images of porous samples revealed a film composed principally of Cu and Fe, Al, followed by a Ni-rich zone, whose thickness was approximately 1.5 µm, which depended on the porous design but was not influenced significantly by the heat treatment. Additionally, by incorporating porosity, the corrosion rate of NAB samples increased slightly.

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In this study, graphite, graphene, and hydrophilic-treated graphene electrodes were evaluated in a dual-chamber microbial fuel cell (DC-MFC). Free-oxygen conditions were promoted in anodic and cathodic chambers. Hydrochloric acid at 0.1 M and pH 1.1 was used as a catholyte, in addition to deionized water in the cathodic chamber. Domestic wastewater was used as a substrate, and a DuPontTM Nafion 117 membrane was used as a proton exchange membrane. The maximum power density of 32.07 mW·m-2 was obtained using hydrophilic-treated graphene electrodes and hydrochloric acid as catholyte. This power density was 1.4-fold and 32-fold greater than that of graphene (22.15 mW·m-2) and graphite (1.02 mW·m-2), respectively, under the same operational conditions. In addition, the maximum organic matter removal efficiencies of 69.8% and 75.5% were obtained using hydrophilic-treated graphene electrodes, for hydrochloric acid catholyte and deionized water, respectively. Therefore, the results suggest that the use of hydrophilic-treated graphene functioning as electrodes in DC-MFCs, and hydrochloric acid as a catholyte, favored power density when domestic wastewater is degraded. This opens up new possibilities for improving DC-MFC performance through the selection of suitable new electrode materials and catholytes.

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H2S is a gaseous compound that contributes to air pollution. In this work, the electrochemical oxidation treatment of gaseous streams polluted with H2S is evaluated using a jet mixer and electrochemical cell device, in which the performance of electrolytic and electro-Fenton assisted absorption processes are compared. Results demonstrate the feasibility of both processes to remove H2S, reaching coulombic efficiencies of nearly 100% in the electrolytic assisted absorption, and 70-80% in the electro-Fenton assisted absorption. Aqueous solutions containing phosphate salts as electrolyte were found to be suitable as absorbents for the process. Efficiency in the cathodic production of H2O2 in these solutions using the experimental device was found to be as high as 32.8% (1.184 mgH2O2/min) at 12 °C and atmospheric pressure. Sequential formation of SO2 and SO3 is obtained by the oxidation of H2S contained in the gas. These species are hydrolysed, and a part remained in the absorbent as SO32- and SO42-, while the rest is dragged in the outlet gas. SO3 production is promoted by electrolytic assisted absorption and polysulphides by the electro-Fenton technology. Low concentrations of elemental sulphur are detected in the solid suspensions formed during the process.

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Indigo Blue (IB) is a dye widely used by the textile sector for dyeing cellulose cotton fibers and jeans, being considered a recalcitrant substance, and therefore resistant to traditional treatments. Several methodologies are reported in the literature for the removal or degradation of dyes from the aqueous medium, among which photoelectrocatalysis stands out, which presents promising results in the degradation of dyes when a dimensionally stable anode (DSA) is used as a photoanode. In the present work, we sought to investigate the efficiency of a Ti/RuO2-TiO2 DSA modified with tin and tantalum for the degradation of Indigo Blue dye by photoelectrocatalysis. For this, electrodes were prepared by the thermal decomposition method and then a physical-chemical and electrochemical analysis of the material was carried out. The composition Ti/RuO2-TiO2-SnO2Ta2O5 (30:40:10:20) was compared to Ti/RuO2-TiO2 (30:70) in the photocatalysis, electrocatalysis, and photoelectrocatalysis tests. The photocatalysis was able to degrade only 63% of the IB at a concentration of 100 mg L-1 in 3 h, whereas the electrocatalysis and photoelectrocatalysis were able to degrade 100% of the IB at the same initial concentration in 65 and 60 min, respectively.

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Microbial fuel cells (MFCs) are a technology that can be applied to both the wastewater treatment and bioenergy generation. This work discusses the contribution of improvements regarding the configurations, electrode materials, membrane materials, electron transfer mechanisms, and materials cost on the current and future development of MFCs. Analysis of the most recent scientific publications on the field denotes that dual-chamber MFCs configuration offers the greatest potential due to the excellent ability to be adapted to different operating environments. Carbon-based materials show the best performance, biocompatibility of carbon-brush anode favors the formation of the biofilm in a mixed consortium and in wastewater as a substrate resembles the conditions of real scenarios. Carbon-cloth cathode modified with nanotechnology favors the conductive properties of the electrode. Ceramic clay membranes emerge as an interesting low-cost membrane with a proton conductivity of 0.0817 S cm-1, close to that obtained with the Nafion membrane. The use of nanotechnology in the electrodes also enhances electron transfer in MFCs. It increases the active sites at the anode and improves the interface with microorganisms. At the cathode, it favors its catalytic properties and the oxygen reduction reaction. These features together favor MFCs performance through energy production and substrate degradation with values above 2.0 W m-2 and 90% respectively. All the recent advances in MFCs are gradually contributing to enable technological alternatives that, in addition to wastewater treatment, generate energy in a sustainable manner. It is important to continue the research efforts worldwide to make MFCs an available and affordable technology for industry and society.

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The combination of energy and chemical conversion can be achieved by designing glycerol fuel cells. However, the anode must promote the reaction at onset potentials low enough to allow a spontaneous reaction, when coupled to the cathodic reaction, and must be selective. Here, we build a three-dimensional (3D)-printed glycerol microfluidic fuel cell that produces power concomitantly to glycolate and formate at zero bias. The balance between energy and the two carbonyl compounds is tuned by decorating the Pt/C/CP anode in situ (before feeding the cell reactants) or in operando (while feeding the cell with reactants) with Bi. The Bi-modified anodes improve glycerol conversion and output power while decreasing the formation of the carbonyl compounds. The in operando method builds dendrites of rodlike Bi oxides that are inactive for the anodic reaction and cover active sites. The in situ strategy promotes homogeneous Bi decoration, decreasing activation losses, increasing the open-circuit voltage to 1.0 V, and augmenting maximum power density 6.5 times and the glycerol conversion to 72% at 25 °C while producing 0.2 mmoL L-1 of glycolate and formate (each) at 100 µL min-1. Such a performance is attributed to the low CO poisoning of the anode, which leads the glycerol electrooxidation toward a more complete reaction, harvesting more electrons at the device. Printing the microfluidic fuel cell takes 23 min and costs ∼US$1.85 and can be used for other coupled reactions since the methods of modification presented here are applied to any existing and assembled systems.

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BACKGROUND Synthesis of selenium nanoparticles from selenite by Shewanella sp. HN-41 demonstrated that particle size depended on the reaction time and biomass of cells. The slow reaction and low biomass tended to form small particles. In this study, Shewanella sp. HN-41 was introduced into the anode of a nonexternal circuit bioelectrochemical system (nec_BES) to convert chemical energy from lactate to low electron current to the cathode, where selenite was reduced. RESULTS Our experiment with two systems, one bioelectrochemical system with a cathode flushed with nitrogen and the other with a no-nitrogen-flushing cathode, showed that the former could not produce Se nanoparticles after 21 d, but the latter formed them with an average size of 37.7 nm. The SEM and TEM images demonstrated that the particle size of 10 nm occupied over 10% and most of the particles were in the range of 30­60 nm. The XRD result and SAED image demonstrated no clear peaks of crystal and proved that the Se nanoparticles are amorphous. CONCLUSIONS : The clean Se nanoparticles were synthesized and completely separated from bacterial cells in the bioelectrochemical system. This study opened a new approach for the biological synthesis of metal nanoparticles. Finally, the Se products in the range of 30­60 nm can be tested for antimicrobial activities in medical applications

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The environmental persistence of hexachlorobenzene (HCB) is a challenge that promotes studies for efficient treatment alternatives to minimize its environmental impact. Here, we evaluated the HCB removal by electrochemical, biological, and combined approaches. The electrochemical treatment of 4 µM HCB solutions was performed using a synthesized Ti/RuO2-IrO2-TiO2 anode, while the biological treatment using mangrove-isolated bacteria was at 24, 48, and 72 h. The HCB degradability was assessed by analyzing chemical oxygen demand (COD), microbial growth capacity in media supplemented with HCB as the only carbon source, gas chromatography, and ecotoxicity assay after treatments. The synthesized anode showed a high voltammetric charge and catalytic activity, favoring the HCB biodegradability. All bacterial isolates exhibited the ability to metabolize HCB, especially Bacillus sp. and Micrococcus luteus. The HCB degradation efficiency of the combined electrochemical-biological treatment was evidenced by a high COD removal percentage, the non-HCB detection by gas chromatography, and a decrease in ecotoxicity tested with lettuce seeds. The combination of electrochemical pretreatment with microorganism degradation was efficient to remove HCB, thereby opening up prospects for in situ studies of areas contaminated by this recalcitrant compound.

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The effects of the supporting electrolytes (SEs) Na2SO4, NaCl, Na2CO3, NaNO3, and Na3PO4 on the anodic oxidation of norfloxacin (NOR) and ciprofloxacin (CIPRO), assessed by the respective degradation kinetics and byproducts and electrolyzed solution antimicrobial activity, are compared. Galvanostatic anodic oxidations were performed in a filter-press flow cell fitted with a boron-doped diamond anode. Removal rates higher than the theoretical one for a process purely controlled by mass transfer were found for all SEs, indicative of contribution by indirect oxidation processes. However, the removal rates for NaCl were about tenfold higher, with the lowest energy consumption per order (EC O) of targeted pollutant removal rate (ca. 0.7 kW h m-3 order-1), a very competitive performance. The TOC removal rates were also affected by the SE, but not as markedly. The antimicrobial activity of the electrolyzed solutions against Escherichia coli showed distinct temporal profiles, depending on the fluoroquinolone and SE. For instance, when Na3PO4 was used, the antimicrobial activity was completely removed for NOR, but none for CIPRO; conversely, when NaCl was used, complete removal was attained only for CIPRO. From LC-MS/MS analyses of Na3PO4 electrolyzed solutions, rupture of the fluoroquinolone ring leading to byproducts with no toxicity against E. coli occurred only for NOR, whereas exactly the opposite occurred for the NaCl solutions. Clearly, the nature of both the SE and the fluoroquinolone influence the oxidation steps of the respective molecule; this was also evidenced by the distinct short-chain carboxylic acids identified in the degradation of NOR and CIPRO.

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This work propose the fabrication and characterization of a Pt microelectrode integrated with a silver quasi-reference counter electrode (Pt/AgQRCE) for real time amperometric measurements of hydrogen peroxide electrochemically generated by water oxidation on Nb-supported boron doped diamond (Ni/BDD) anode. The developed electroanalytical method requires a very small sample volume and has higher sensitivity when compared to the conventional spectrophotometric analysis using ammonium metavanadate. The experiments were performed with Nb/BDD anode applying current densities of 30, 60, 90 and 120 mA cm-2 in 0.10 mol L-1 HClO4 supporting electrolyte showed that H2O2 production increase in the first 90 min of electrolysis and then reaches a plateau in both off-line and real time measurements. For the first 90 min, the electrogeneration of H2O2 exhibited a pseudo zero-order kinetics. The results obtained by the electrochemical amperometric analysis were compared to a spectrophotometric methodology reported on the literature and, at 95% confidence level the two methods do not demonstrated significant difference.

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Alternative routes to degrade dyes are of crucial importance for the environment. Hence, we report the electrochemical removal of indanthrene blue by using a boron-doped diamond anode, focusing on the toxicity of the treated solutions. Different operational conditions were studied, such as current density (5, 10, and 20 mA cm-2) and electrolyte composition (Na2SO4, Na2CO3, and NaNO3). Besides, the pH was monitored throughout the experiment to consider its direct influence on the ecotoxicity effects. The highest electrochemical oxidation efficiency, measured as color removal, was seen in the 180 min condition of electrolysis in 0.033 M Na2SO4, applying 20 mA cm-2, resulting in a color removal of nearly 91% and 40.51 kWh m-3 of energy consumption. The toxicity towards Lactuca sativa depends solely on pH variations being indifferent to color removal. While the inhibition concentration (IC50) for Raphidocelis subcapitata increases 20% after treatment (in optimized conditions), suggesting that the byproducts are more toxic for this specific organism. Our data highlight the importance of analyzing the toxicity towards various organisms to understand the toxic effect of the treatment applied.

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Glucocorticoids are widely used to treat a variety of diseases. Consequently, these compounds have been found in water and wastewater matrix. Despite studies have proven its toxicity, just a few works investigate techniques to degrade and mineralize them. To solve this issue, this work presents the degradation and mineralization of prednisone (PRED) by electrochemical advanced oxidation (EAO) using a boron-doped diamond supported on niobium (Nb/BDD) anode in synthetic and real wastewater. Cyclic voltammetry (CV) was performed to investigate the PRED oxidation mechanisms. CV suggest that PRED will be oxidized via HO• and other oxidants generated from the ions present in the liquid matrix (S2O82-, SO4•-, HClO, ClO- etc.). Different EAO conditions as initial pH (3, 7 and 11) and applied current densities (5, 10 and 20 mA cm-2) were evaluated. The best result was obtained at alkaline pH (11) and a current density of 20 mA cm-2, achieving 78% of degradation and 42% of mineralization. Using the best conditions, the EAO was applied as a polishing treatment stage to remove PRED from a biological pre-treated municipal wastewater spiked with PRED. The results indicate that EAO applied in the real matrix provides better results than the synthetic solution, probably associated with the presence of ions that can be electrochemically converted into oxidant species, resulting in higher kinetic constant, mineralization current efficiency and lower energetic consumption. Therefore, the EAO process without the addition of chemicals has proven to be an effective alternative as a tertiary treatment of municipal wastewater contaminated with PRED.

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The performances of distinct BDD anodes (boron doping of 100, 500 and 2500 ppm, with sp3/sp2 carbon ratios of 215, 325, and 284, respectively) in the electrochemical degradation of ciprofloxacin - CIP (0.5 L of 50 mg L-1 in 0.10 M Na2SO4, at 25 °C) were comparatively assessed using a recirculating flow system with a filter-press reactor. Performance was assessed by monitoring the CIP and total organic carbon (TOC) concentrations, oxidation intermediates, and antimicrobial activity against Escherichia coli as a function of electrolysis time. CIP removal was strongly affected by the solution pH (kept fixed), flow conditions, and current density; similar trends were obtained independently of the BDD anode used, but the BDD100 anode yielded the best results. Enhanced mass transport was achieved at a low flow rate by promoting the solution turbulence within the reactor. The fastest complete CIP removal (within 20 min) was attained at j = 30 mA cm-2, pH = 10.0, and qV = 2.5 L min-1 + bypass turbulence promotion. TOC removal was practically accomplished only after 10 h of electrolysis, with quite similar performances by the distinct BDD anodes. Five initial oxidation intermediates were identified (263 ≤ m/z ≤ 348), whereas only two terminal oxidation intermediates were detected (oxamic and formic acids). The antimicrobial activity of the electrolyzed CIP solution was almost completely removed within 10 h of electrolysis. The characteristics of the BDD anodes only had a marked effect on the CIP removal rate (best performance by the least-doped anode), contrasting with other data in the literature.

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Microbial life is predominantly observed as biofilms, which are a sessile aggregation of microbial cells formed in response to stress conditions. The microtiter dish biofilm formation assay is one of the most important methods of studying biofilm formation. In this study, the assay has been improvised to allow easy detection of biofilm formation on different substrata. The method has then been used to study growth conditions that affect biofilm formation, viz., the effect of pH, temperature, shaking conditions, and the carbon source provided. Glass, cellulose acetate, and carbon cloth materials were used as substrata to study biofilm development under the above conditions. The method was then extended to determine biofilm formation on the anodes of a microbial fuel cell in order to study the effect of biofilm formation on power production. A high correlation was observed between biofilm formation and power density (r = 0.951). When the electrode containing a biofilm was replaced with another electrode without biofilm, the average power density dropped from 59.55 to 5.76 mW/m2. This method offers an easy way to study the suitability of different materials to support biofilm formation. Growth conditions determining biofilm formation can be studied using this method. This method also offers a non-invasive way to determine biofilm formation on anodes of microbial fuel cells and preserves the anode for further studies.

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The electrochemical degradation of ciprofloxacin-CIP (50 mg L-1 in 0.10 mol L-1 Na2SO4) was investigated using a double-sided Ti-Pt/ß-PbO2 anode in a filter-press flow reactor, with identification of oxidation intermediates and follow-up of antimicrobial activity against Escherichia coli. The effect of solution pH, flow rate, current density, and temperature on the CIP removal rate was evaluated. All of these parameters did affect the CIP removal performance; thus, optimized electrolysis conditions were further explored: pH = 10, qV = 6.5 L min-1, j = 30 mA cm-2, and θ = 25 °C. Therefore, CIP was removed within 2 h, whereas ~75% of the total organic carbon concentration (TOC) was removed after 5 h and then, the solution no longer presented antimicrobial activity. When the electrochemical degradation of CIP was investigated using a single-sided boron-doped diamond (BDD) anode, its performance in TOC removal was similar to that of the Ti-Pt/ß-PbO2 anode; considering the higher oxidation power of BDD, the surprisingly good comparative performance of the Ti-Pt/ß-PbO2 anode was ascribed to significantly better hydrodynamic conditions attained in the filter-press reactor used with this electrode. Five initial oxidation intermediates were identified by LC-MS/MS and completely removed after 4 h of electrolysis; since they have also been determined in other degradation processes, there must be similarities in the involved oxidation mechanisms. Five terminal oxidation intermediates (acetic, formic, oxamic, propionic, and succinic acids) were identified by LC-UV and all of them (except acetic acid) were removed after 10 h of electrolysis.

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This paper describes a thermal method to obtain metal oxides on a titanium substrate surface. This adapted Pechini method is a versatile, easy to handle and scalable technique to obtain electrodes for industrial uses, such as Dimensionally Stable Anodes (DSA). This method has advantages over other thermal methods like dip coating or sputtering, as it needs a smaller amount of polymeric mixture than dip coating method to cover the same area and is less expensive than sputtering method. The thermal method described herein to prepare DSA type electrodes of RuO2-ZrO2 doped with Sb2O5 over titanium plates needs no sophisticated equipment as spray pyrolysis technique does; a muffle, ultrasonic equipment, and a hot plate magnetic stirrer are the principal apparatus necessary to carry out the adapted Pechini method. On the other hand, this method allows metal oxides to disperse homogeneously. The cyclic voltammograms showed the stability of DSA, and the accelerated life test allowed establishing its useful life (18.18 years) at a current density of 10 mA cm-2.

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The simultaneous removal of hydrated silica, fluoride and arsenic from deep well water (hydrated silica 72 mgL-1, fluoride 4.4 mgL-1, arsenic 106.2 µgL-1, sulfate 50 mgL-1, phosphate 0.99 mgL-1, pH = 8.2 and conductivity 659 µScm-1) by electrocoagulation (EC) was investigated. The EC was performed in a continuous electrochemical reactor using aluminum plates as sacrificial anodes coupled directly to a jar test device. The effect of current density (4 ≤ j ≤ 8 mA cm-2) and mean linear flow rates in the EC reactor (0.057 ≤ u ≤ 0.57 cm s-1) on the hydrated silica, fluoride, and arsenic removal efficiencies was analyzed. The abatement of hydrated silica was obtained at 8 mA cm-2 and 0.057 cm s-1, while the residual concentrations of F- and As after the same electrolysis were 0.19 mg L-1 and 9.8 µg L-1, satisfying the WHO guidelines for F- (≤1.5 mg L-1) and As (≤10 µg L-1). Spectroscopic analyses on aluminum flocs revealed that they are predominantly composed of aluminum silicates. Arsenates adsorb on aluminum flocs and fluoride replaces a hydroxyl group from aluminum aggregates.

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The destruction of the herbicide chloramben in 0.050 M Na2SO4 solutions at natural pH has been studied by photoelectro-Fenton with UVA light (PEF). The trials were carried out in a cell equipped with an air-diffusion cathode for H2O2 generation and different electrocatalytic anodes, namely active IrO2-based and RuO2-based electrodes and non-active boron-doped diamond (BDD) and PbO2 ones. Similar removal rates were found regardless of the anode nature because the herbicide was mainly oxidized by OH formed from Fenton's reaction, which was enhanced by UVA-induced photo-Fenton reaction. The use of an IrO2-based anode led to almost total mineralization at high current density, as also occurred with the powerful BDD anode, since photoactive intermediates originated from OH-mediated oxidation were degraded under irradiation with UVA light. The good performance of the IrO2-based anode in PEF was confirmed at different current densities and herbicide concentrations. The presence of Cl- in the medium caused a slight deceleration of herbicide removal as well as mineralization inhibition, owing to the production of active chlorine with consequent formation of persistent chloroderivatives. Seven aromatic products along with oxalic and oxamic acids were identified in sulfate medium. Five aromatic derivatives were detected in Cl--containing matrix, corroborating the generation of organochlorine compounds. In secondary effluent, larger mineralization was achieved by PEF with a BDD anode due to its high oxidation ability to destroy the chloroderivatives, although an acceptable performance was also obtained using an IrO2-based anode.

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