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This study aims to assess the electrochemical generation of hydrogen peroxide and hydroxyl radicals (*OH) using carbon cathodes synthesized from three different lignocellulosic residues, Phragmites australis (PA), Cladium mariscus (CM) and Typha domingensis (TD). These vegetal species are commonly used in natural wetlands and phytoremediation processes and can accumulate recalcitrant pollutants within these treatment processes, generating a waste that should be properly managed. To convert these residues into valuable carbon materials, they underwent hydrothermal carbonization (HTC) followed by either chemical activation with KOH or pyrolysis at 1000 ºC. The best results were obtained with chemically activated materials, yielding a maximum H 2 O 2 concentration of 313 mg L−1 with the carbon cathode produced from PA. The specific surface area, oxygenated functional groups and presence of structural defects in carbonous structures, were key parameters related to a good performance as catalysts towards the 2e- Oxygen Reduction Reaction (ORR). It was also demonstrated, in comparison with previous studies, that the presence of heavy metals in the structure of the lignocellulosic residue enhanced the decomposition of H 2 O 2 into *OH. However, in the study of the degradation of a model organic contaminant as methylene blue (MB), it was shown that these *OH were not the main contributors to degradation, as direct H 2 O 2 chemical degradation and adsorption on the carbon materials played the most significant role. Therefore, the outstanding capacity of these lignocellulosic residues as catalysts for the electrogeneration of H 2 O 2 was confirmed, suggesting their potential future application in advanced oxidation processes for water decontamination. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract In this work, the valorization of brines, with concentrations similar to those produced by reverse osmosis or electrodialysis processes, by electrolysis with diamond anodes is evaluated. To do this, synthetic brines made from solutions of NaCl (with target concentrations ranging from 1.0 to 2.0 M and an additional test at 5.0 M) were used as the raw material for the electrochemical production of perchlorate using commercial electrochemical cells equipped with boron-doped diamond (BDD) anodes. The effect of key parameters on the rate and efficiency of perchlorate production was evaluated. The results show that it is possible to transform more than 80% of the initial chloride concentration into perchlorate, with current efficiencies higher than 70% regardless of the initial concentration of sodium chloride contained in the brine. Moreover, it was observed that both hypochlorite and chlorate were produced almost simultaneously at the beginning of electrolysis, while perchlorate was only produced when a certain value of applied electric charge was passed through the system. The results obtained were essentially independent of the concentration of NaCl, as the high concentrations used in this study avoided mass transfer limitations. Moreover, the specific energy cost of perchlorate production was estimated to range from 26.14 kWh kg−1 (for 2.0 M and 1000 A m−2) to 56.10 kWh kg−1 (for 1.0 M and 2000 A m−2). According to the results obtained, the electrochemical production of perchlorate by BDD electrochemical oxidation stands out as a promising novel technology for the valorization of the brine produced in reverse osmosis or electrodialysis processes. Graphical abstract Image 1 Highlights • Perchlorate is efficiently produced from highly concentrated NaCl by electrolysis. • High current efficiency and conversion to perchlorate were obtained. • A threshold of applied charge is required to produce perchlorate. • The energy consumption of perchlorate production ranges from 26.14–56.10 kWh kg−1. [ABSTRACT FROM AUTHOR]

Abstract The performance of a novel pressurized-jet microfluidic flow-through electrolyzer for the production of aqueous solution of H 2 O 2 is assessed in this work. The reactor design is based on three aspects i) minimizing ohmic drops, by reducing the interelectrode gap to 150 μm and the use of a Duocel® aluminum foam as cathodic support; ii) maximizing mass transport, due to the use of three-dimensional electrodes fed in flow-through and iii) optimizing the aeration system coupling a pressurized circuit and a jet aerator. Results show that H 2 O 2 can be produced with an instantaneous current efficiency of ≅ 100% up to 20 mA cm−3 and a corresponding production rate of 13.1 mg H 2 O 2 h−1 cm−3 in a cathode of 16.5 cm3. Low ohmic resistances were measured even in low-conductive electrolytes, as for example 6 Ω in 0.0035 M Na 2 SO 4 (0.7 mS cm−1). The electrical energy consumption of 3.65 kWh kg H 2 O 2 −1 at 10 mA cm−3 in 0.05 M Na 2 SO 4 is the lowest reported so far in neutral-acid medium, confirming the cost-effectiveness of the system. A preliminary scale-up by increasing the cathode volume three times (up to 49.5 cm3) allowed the production rate to be multiplied by the same factor and confirms that the system is scalable. Theoretical calculations suggest that the cathode could be expanded up to 3600 cm3 (1 m thickness) under those aeration conditions (6 bar and 160 dm3 h−1 recirculation flow). Graphical abstract Image 1 Highlights • New cell combines low ohmic drop, high mass transfer and a powerful aeration. • An instantaneous current efficiency of 100% is measured up to 20 mA cm−3 • An outstanding low ohmic drop of 6 Ω even in low conductive medium of 0.7 mS cm−1 • The lowest energy consumption so far in acid-neutral medium is reported. • The system is potentially scalable up to a volume of 3600 cm3 with this aeration. [ABSTRACT FROM AUTHOR]

In this work, the disinfection of highly faecal-polluted surface water was studied using a new electrochemical cell (CabECO ® cell, manufactured by CONDIAS) specifically designed to produce ozone in water with very low conductivity. The disinfection tests were carried out in a discontinuous mode to evaluate the influence of the electrode current charge passed. The effect of the current density was also studied in order to optimize the disinfection conditions and to simultaneously prevent the formation of undesirable by-products (chlorates and perchlorates) during the electrolysis. The results demonstrate that this technology is robust and efficient, and it can suitably disinfect water. During electrolysis, the chloride contained in the water was oxidized to hypochlorite, and this compound was combined with ammonia to form chloramines. Both hypochlorite and chloramines (formed by the well-known break point reaction) promoted persistent disinfection and seemed to be mainly responsible for the disinfection attained during the electrochemical process. Chlorate and perchlorate could also be produced, although the low concentrations of chloride in the tested water made them irrelevant. The removal of the total organic carbon under the applied operating conditions was not very efficient (although it reached 50% in 2 h) and the production of trihalomethanes was very low, below 100 ppb for all tests. [ABSTRACT FROM AUTHOR]

The improvement in the treatment efficiency of diluted effluents is one of the great challenges faced by electrochemical technology nowadays. In the present work, it is aimed to develop an electrochemical cell for the simultaneous concentration and degradation of ionic organic pollutants. This combined cell (so called EDEO device) integrates the concentration of the organic by electrodialysis (ED) with its electro-oxidation (EO). For the particular case of the 2,4-dichlorophenoxyacetic acid (2,4-D), the performance of the cell has been tested with two anode materials (boron-doped diamond, BDD and mixed mineral oxides, MMO) and with two supporting electrolytes in order to explore four combinations that are expected to cover a wide range of possible actual scenarios. Results demonstrate that the combined EDEO process exhibits a degradation rate and a mineralization current efficiency markedly higher than the equivalent EO device when working with MMO anodes, either with NaCl or with Na 2 SO 4 . It was checked that the use of a BDD anode clearly increases the efficiency and the rate of the treatment due to the formation of strong oxidants. In this case, the effect of working with the combined EDEO in the rate of 2,4-D degradation is negligible because the 2,4-D transport rate becomes comparable to the degradation rate, being the combined process unable to generate a concentration greater than that accounted in the single EO device. [ABSTRACT FROM AUTHOR]

In this work, the removal of Procion Red MX-5B dye by electrochemical oxidation with boron doped diamond (BDD) anodes was investigated. The impact of current density, flow rate, initial pH, and supporting electrolyte was evaluated on dye and organic matter removal. Furthermore, the use of dimensionally stable anodes (DSA) was tested to evaluate process performance. Results show that after 240 min, it is possible to achieve full dye and COD (Chemical Oxygen Demand) removal, regardless of applied current density. This is due to the generation of powerful oxidants – i.e. hydroxyl radicals and peroxodisulfate–, which attack the organic matter in the wastewater, promoting its complete degradation. However, process efficiency increases when using lower current densities (10 mA cm −2 ): electric charges of about 5 Ah dm −3 are sufficient to fully remove both dye and COD, while charges higher than 15 Ah dm −3 are required when working at higher current densities (>30 mA cm −2 ). This fact is related to the production of large amounts of hydroxyl radicals, which are wasted in other reactions at higher current densities. On the other hand, higher flow rates (300 dm 3  h −1 ) promote Procion Red MX-5B and organic matter degradation, due to improved mass transfer within the system. Regarding the impact of initial pH on dye removal, no significant differences were observed. Conversely, COD is clearly affected by this parameter: it is only possible to fully remove the organic matter when working at natural pH. Finally, with DSA anodes, higher dye removal efficiencies are attained than with BDD electrodes, when 100 mg dm −3 chlorides are added to the supporting electrolyte. Likewise, higher chloride concentration (100–1000 mg dm −3 ) was observed to enhance process efficiency when using DSA as anode material. However, during electrolysis with both BDD and DSA, chloride ions in the supporting electrolyte promote the production of intermediate organochlorinated compounds. Therefore, under these conditions, no full organic matter removal can be achieved, regardless of the anode material employed. [ABSTRACT FROM AUTHOR]

This work describes a new process for the efficient electrochemical production of peroxoacetic acid (PAA) from aqueous acetic acid solutions, coupling the cathodic production of hydrogen peroxide and the oxidation of acetic acid at the anode. The key role of the production of hydrogen peroxide in the accumulation of PAA is demonstrated, together with the importance of the anode material. Thus, boron doped diamond (BDD) anodes exhibited better performance than dimensionally stable anodes (DSA ® ) because of the promotion of the oxidation of acetic acid via hydroxyl radicals. Moreover, it was observed that the production yield of peroxoacetic acid increases with current density until a threshold (27 A m −2 for BDD anodes), from which decomposition of hydrogen peroxide and PAA become dominant and the efficiency of the process decreases for higher current densities. Finally, it was found that the configuration of the electrochemical cell played an unexpected key role in the performance of the process due to the dissimilar efficiency in the use of the hydrogen peroxide electrochemically produced. [ABSTRACT FROM AUTHOR]

Trematode blood flukes of the genus Cardicola are potentially lethal in bluefin tuna cultures. The present study proposed a new method to detect aporocotylid eggs in tuna gills. Aporocotylid eggs were detected by analysing a pair of gill filaments of five transversal areas of the eight holobranches of one hundred Atlantic bluefin tuna and observed with glycerol and a stereomicroscope with an oblique brightfield. Data were gathered according to holobranches, transversal areas and their combination. Eggs were uniformly distributed among the holobranches, but they had the highest prevalence in the second and fifth transversal areas, which is controversial with respect to previous studies of egg distribution. An abbreviated method called the T-two test, which had the highest sensitivity (96.8%), is proposed for the detection of Cardicola spp. infections instead of the analysis all the holobranches. The T-two test limits the time and cost of the egg parasite screening analysis. The analyses of ten samples could be sufficient to detect the presence of parasites in farmed bluefin tuna; fish from the wild are expected to be less infected and more samples (45) would therefore be necessary. [ABSTRACT FROM AUTHOR]

This work focuses on the disinfection actual urban wastewater by the combination of ultrasound (US) irradiation and electrodisinfection with Dimensionally Stable Anodes (DSA). First, the inactivation of Escherichia coli ( E. coli ) during the sonochemical disinfection was studied at increasing ultrasound power. Results showed that it was not possible to achieve a complete disinfection, even at the highest US power (200 W) dosed by the experimental device used. Next, the electrodisinfection with DSA anodes at different current densities was studied, finding that it was necessary a minimum current density of 11.46 A m −2 to reach the complete disinfection. Finally, an integrated sonoelectrodisinfection process was studied. Results showed a synergistic effect when coupling US irradiation with DSA electrodisinfection, with a synergy coefficient higher than 200% of the disinfection rate attained for the highest US power applied. In this process, hypochlorite and chloramines were identified as the main reagents for the disinfection process (neither chlorate nor perchlorate were detected), and the presence of trihalomethanes was far below acceptable values. Confirming this synergistic effect with DSA anodes opens the door to novel efficient disinfection processes, limiting the occurrence of hazardous disinfection by-products. [ABSTRACT FROM AUTHOR]

This work focuses on coupling electrocoagulation, with iron electrodes, and UV irradiation (photo-electrocoagulation) for the simultaneous removal of turbidity and E. coli from actual treated municipal wastewaters. Results show that single electrocoagulation behaves as a very efficient technology even using low current densities. E. coli is removed not only by the enmeshment of microorganisms into growing flocs, but also by the attack of electrochemically produced chlorine disinfectant species. Coupling UV irradiation to electrocoagulation with iron electrodes improves the process performance in terms of E. coli and turbidity removal. The effect of current density on process performance was evaluated, finding a synergistic interaction of both techniques at low current density (1.44 A m −2 ) but an antagonistic effect at higher values of current density (7.20 A m −2 ). This antagonistic effect is caused by the less efficient transmission of UV irradiation to the bulk solution due to the increase in the concentration of solids. [ABSTRACT FROM AUTHOR]

Abstract: This work presents an integrated electrodisinfection/electrocoagulation (ED–EC) process for urban wastewater reuse that employs iron bipolar electrodes. Boron doped diamond (BDD) was used as the anode and stainless steel (SS) as the cathode. A perforated iron plate was introduced between the anode and cathode to function as a bipolar electrode. This ED–EC combined cell makes it possible to conduct the simultaneous removal of microbiological content and elimination of turbidity from urban wastewater. The results show that current densities greater than or equal to 6.70 A m−2 enable complete disinfection of the effluent and the removal of more than 90% of its initial turbidity. Hypochlorite and chloramines formed during the ED–EC process were found to be the main compounds responsible for the disinfection process. Furthermore, a cell configuration of cathode (inlet)-anode (outlet) improves the process performance by enhancing turbidity removal. Finally, the influence of the bipolar electrode material (iron or aluminium) was assessed. The results indicate that the efficiency of the electrodisinfection process depends mainly on the anodic material and is not influenced by the material of the bipolar electrode. In contrast, the removal of turbidity is more efficient when using iron as a bipolar electrode, especially at low current densities, due to the formation of a passive layer on the aluminium that hinders the dissolution of the bipolar electrode. [Copyright &y& Elsevier]

Abstract: This paper presents a neuro-evolutionary modelling methodology applied to an electrodeposition process for the recovery of copper and zinc. This technique consists in designing the optimal neural network model using an algorithm obtained through the combination of a multi-objective evolutionary algorithm (NSGA-II) and a local search algorithm (Quasi-Newton). Parametric and structural optimization for feed-forward neural networks are performed determining the optimum number of hidden layers and hidden neurons, the optimum weights and the most appropriate activation functions for the hidden and output layers. Accurate results are obtained in the modelling procedure, with the possibility to choose the adequate model, representing a compromise between performance and complexity. Significant information is obtained by simulation, related to the rate and quality of the electrodeposition process depending of the working conditions. The highest accuracy of the model is obtained for the prediction of copper and zinc concentrations (the most important output variables), a promising result to use the proposed model for the future optimization of the process. Moreover, due to the very different behaviour of copper and zinc in the electrodeposition process, the proposed model could be also successfully used for a wide variety of heavy metal ions. [Copyright &y& Elsevier]

Abstract: In this work, a novel integrated electrochemical process for urban wastewater regeneration is described. The electrochemical cell consists in a Boron Doped Diamond (BDD) or a Dimensionally Stable Anode (DSA) as anode, a Stainless Steel (SS) as cathode and a perforated aluminum plate, which behaves as bipolar electrode, between anode and cathode. Thus, in this cell, it is possible to carry out, at the same time, two different electrochemical processes: electrodisinfection (ED) and electrocoagulation (EC). The treatment of urban wastewater with different anodes and different operating conditions is studied. First of all, in order to check the process performance, experiments with synthetic wastewaters were carried out, showing that it is possible to achieve a 100% of turbidity removal by the electrodissolution of the bipolar electrode. Next, the effect of the current density and the anode material are studied during the ED–EC process of actual effluents. Results show that it is possible to remove Escherichia coli and turbidity simultaneously of an actual effluent from a WasteWater Treatment Facility (WWTF). The use of BDD anodes allows to remove the E. coli completely at an applied electric charge of 0.0077 A h dm−3 when working with a current density of 6.65 A m−2. On the other hand, with DSA anodes, the current density necessary to achieve the total removal of E. coli is higher (11.12 A m−2) than that required with BDD anodes. Finally, the influence of cell flow path and flow rate have been studied. Results show that the performance of the process strongly depends on the characteristics of the initial effluent (E. coli concentration and Cl−/NH4 + initial ratio) and that a cell configuration cathode (inlet)–anode (outlet) and a higher flow rate enhance the removal of the turbidity from the treated effluent. [Copyright &y& Elsevier]

• High metal content phytoremediation waste was valorized for the production of H 2 O 2. • Hydrothermal carbonization+activation is a suitable technique for valorization. • Hydrochar activated by KOH (HC-KOH) showed the best electrochemical behavior. • H 2 O 2 accumulation with HC-KOH was close to 70% that of vulcan XC72 (CB). • HC-KOH and HC1000 (activated at 1000ºC) enhance (40%) the production of OH· vs CB. A circular economy approach was followed to convert biomass wastes polluted with metals (obtained from phytoremediation processes) to generate electroactive carbon materials to be used in the electrochemical production of hydrogen peroxide. Carbon materials were pretreated using hydrothermal carbonization at 200ºC and 130 g soil mL−1 water and post treated through pyrolysis at different temperatures (300ºC, 500ºC and 1000ºC) and using different chemical precursors as KOH or H 3 PO 4. These materials would modify the carbon paper (CP) cathodes to substitute the commonly used carbon black (CB), that comes from fossil fuels. Porosity, thermochemical behavior, electrical conductivity, electrocatalytic response and H 2 O 2 accumulation tests were evaluated to determine the potential performance of these materials in the electrochemical production of hydrogen peroxide. Delays in mass losses observed in thermogravimetric studies indicate the improvement of the thermal stability of materials which are related with the highest electrical conductivity (that correspond to hydrochar pyrolyzed at 1000 ºC). High specific surface areas (1097 and 704 m2/g) were also found with hydrochars treated with chemical precursors with values even superior to commercial CB. Results show that all activated hydrochars present electrocatalytic activity towards the production of hydrogen peroxide and that the materials chemically activated with KOH can achieve a 70% of the H 2 O 2 production obtained with commercial CB. Moreover, it was found that the presence of metals in the synthesized materials may promote a Fenton-like reaction, increasing by 40% the generation of hydroxyl radicals with respect to commercial CB. This paramount finding opens the window for the use of this phytoremediation waste to produce sustainable electrode materials for upgraded electrochemical advanced oxidation processes. [Display omitted] [ABSTRACT FROM AUTHOR]

The electrochemical generation of H 2 O 2 can be performed in aqueous solutions by cathodic reduction at carbonaceous cathodes of oxygen coming from air. The performances of the process in terms of concentration of H 2 O 2 and current efficiency (CE) are limited by the low solubility of oxygen in water at atmospheric pressure. However, the solubility of oxygen can be increased upon enhancing the air pressure. The effect of pressure on the electrochemical generation of hydrogen peroxide was studied in undivided cells changing the pressure from 0 to 30 relative bar and the current density from 1 to 100 mA cm −2 . Simple carbon felt and compact graphite cathodes were first used. A dramatic effect of the pressure was shown: at carbon felt a concentration of hydrogen peroxide slightly lower than 30 mM was obtained by working at 30 bar and 20 mA cm −2 , about two orders of magnitude higher than that achieved at atmospheric pressure, as a result of mass transport intensification. The utilization of both a modified carbon felt (with carbon black and polytetrafluoroethylene) and relatively low pressures allowed to further enhance the generation of H 2 O 2 and the CE. Under the best conditions (30 bar and 100 mA cm −2 ), concentrations up to 225 mM together with the highest production rate (1.84 mmol H 2 O 2 cm −2 h −1 and 98.9% CE) in an electrolytic system fed with air are reported. [ABSTRACT FROM AUTHOR]

In this work, the disinfection of the effluent of the secondary treatment of a municipal wastewater treatment plant is studied using two stacks of commercial electrochemical cells powered with very low current densities (0.14–10 A m −2 ), in order to prevent the formation of chlorates and perchlorates during the electrolysis. Results demonstrate that this technology is robust and efficient and it can attain the complete disinfection of wastewater even at very low current densities. These low current densities are high enough to produce hypochlorite and chloramines (when ammonium is present in solution), being the disinfection process more efficient when the concentration of chloramines is higher. Therefore, the presence of hypochlorite together with higher concentrations of chloramines significantly improve the removal of microorganisms. In comparing the two stacks studied in this work, it was obtained that commercial DiaCell stacks containing bipolar connected electrodes are more efficient than those containing monopolar-connected electrodes for the disinfection. Differences are explained in terms of the higher cell voltage applied in that stack (higher current density in bipolar stack) that results in (1) an improved reduction of nitrates to ammonium (BDD cathode in bipolar stack) with the latter formation of chloramines as the main positive effect and (2) in the increase in the power consumed as the primary negative consequence. [ABSTRACT FROM AUTHOR]

In this work, it is evaluated the fixation of carbon dioxide using the alkali generated in the chloralkaline process, as a new way to face the treatment of highly saline wastewater, in which it is aimed not to separate the wastewater into concentrated and diluted streams but to recover value-added products (VAPs) while contributing to minimize the carbon fingerprint of other processes. The electrolytic process is combined with a reactive absorption and with a crystallization, demonstrating the formation of pure nahcolite, hypochlorite (or chlorine) and hydrogen from the waste. Carbon dioxide is captured with a current efficiency over 90% and the energy required is around 0.65 kWh kg−1, which is very promising from the view point of sustainability, considering that the system can be easily powered with green energies. [Display omitted] • CO 2 is electrochemically captured with a current efficiency of 93%. • The system is not mass transfer limited within the range of concentrations tested. • An almost pure NaHCO 3 solid is obtained by cooling the CO 2 -enriched solution. • The energy cost of CO 2 capture is estimated to be 0.65 kWh kg−1. • The efficiency hypochlorite production increases with current density. [ABSTRACT FROM AUTHOR]

• An undivided cell is a versatile device to produce oxygen-based oxidants. • Higher pressure lowers ozone accumulation in the electrochemical cell. • Pressure has a negligible influence on the production of hydroxyl radicals. • Peroxone and peroxo-salts productions are crucial to understand the process. • BDD/graphite offers the best performance for hydroxyl radicals production. This work is focused on the characterization of the production of ozone, hydrogen peroxide and hydroxyl radicals (peroxone) in pressurized undivided electrochemical cells. BDD and MMO electrodes were compared as anodes and RVC, graphite and stainless steel as cathodes. Gauge pressures in the range 2–4 bar were applied. Results demonstrate the complexity in the production of oxidants in an undivided cell, allowing to propose a model of the set of reactions (both electrochemical and in the bulk) occurring in the system. A higher pressure decreases the accumulation of ozone meanwhile hydrogen peroxide production is maximized at intermediate values of pressure. Combining BDD and graphite is the best combination for enhancing the production of hydroxyl radicals for which a negligible influence of pressure was observed. These results would allow to select the proper design to maximize the efficiency in the production of each of the oxidants studied. [Display omitted] [ABSTRACT FROM AUTHOR]