Search

Made available in DSpace on 2020-12-12T01:17:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-05-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Hydrogen peroxide (H2O2) is one of the most popular and widely used oxidants. Among the wide range of synthesis techniques used for the production of H2O2; the electrochemical method allows the use of gas diffusion electrodes to generate H2O2 without limiting the low solubility of O2 in water. The present work reports the modification of carbon black with quinone, where the generation of H2O2 occurs in an electrochemical/chemical mechanism. The results obtained by this technique were found to be highly promising. The use of the organic compound 1,2-dihydroxyanthraquinone to modify carbon black electrode resulted in greater production of H2O2. Carbon black electrode modified with 1% of 1,2-dihydroxyanthraquinone yielded 298 mg L−1 of H2O2 at the end of 90 min of experiment, reaching an electrical efficiency of approximately 25.5%. Based on the findings of this study, H2O2 generation is found to be directly associated with the chemical structure of the carbon modifier and not solely related to the presence of quinone groups. [Figure not available: see fulltext.]. Lorena School of Engineering University of São Paulo (USP), Estrada Municipal do Campinho sn São Carlos Institute of Chemistry University of São Paulo (USP), Av Trabalhador São-carlense 400 Faculty of Science and Engineering São Paulo State University (UNESP), Rua Domingos da Costa Lopes 780 Faculty of Mechanical Engineering State University of Campinas (UNICAMP), Rua Mendeleyev 200 Faculty of Science and Engineering São Paulo State University (UNESP), Rua Domingos da Costa Lopes 780 FAPESP: 2011/14314-1 FAPESP: 2013/02762-5 FAPESP: 2014/50945-4 FAPESP: 2016/12597-0 FAPESP: 2016/22115-2 FAPESP: 2017/10118-0 FAPESP: 2019/00239-0 CNPq: 302874/2017-8 CNPq: 427452/2018-0 CNPq: 465571/2014-0

After designing and constructing an electrochemical reactor with concentric electrodes and tangential feed (RECT), it is necessary to characterize it and to study its performance. The experimental study of the residence time distribution (RTD) was conducted for flow rates of 2.78 × 10–6 m3 s–1, 8.33 × 10–6 m3 s–1 and 13.9 × 10–6 m3 s–1. According to the values obtained from the Pe number (0.67–1.52), the RECT fits as tubular with great dispersion. The determined empirical correlation (Sh = 18.16 Re0.50 Sc0.33) showed a laminar flow behavior in the range of Reynolds number (Re) between 23 and 117. In order to use RECT in effluent treatment, an electrochemical oxidation study of the Diuron model molecule (Nortox®) was performed to analyze reactor performance in a closed system with total reflux. A decay kinetics of pseudo-first order was associated with the decay of the concentration of diuron and 30% mineralization in 180 min of process were obtained, having a total volume of 4 × 10–3 m3 and an initial concentration of commercial Diuron in 215.83 mg dm–3. Eleven by-products were identified by HPLC–MS analysis and, from this, it was possible to propose a route of degradation of the diuron. From these observations, it can be inferred that the studied electrochemical reactor had applicability in the degradation of recalcitrant compounds, as is the case of commercial diuron. Make some changes in the electrochemical reactor studied and other advanced oxidative processes, such as electro-Fenton, can be associated with the studied system to achieve a better conversion efficiency.

Aqueous mixtures of methyl, ethyl and propyl paraben (MeP, EtP and PrP) prepared in real urban wastewater with low conductivity were treated by solar photoelectro-Fenton (SPEF) process at low input current ( j = 10 mA cm −2 ) using a pre-pilot plant with an electrochemical reactor equipped with an air-diffusion cathode to electrogenerate H 2 O 2 and a boron-doped diamond (BDD) or RuO 2 -based anode. Comparative trials in simulated water matrices with or without Cl − in the absence of natural organic matter (NOM) always led to a slower decay of parabens concentration and total organic carbon (TOC). This was mainly due to the superior regeneration of Fe 2+ from photoreduction of Fe(III) complexes formed with NOM in real wastewater compared to that from Fe(OH) 2+ . In all matrices, a catalyst concentration as low as 0.20 mM Fe 2+ was enough to ensure the production of OH in the bulk from Fenton’s reaction. SPEF with BDD yielded a complete removal of parabens in 180 min and 66% mineralization at 240 min. This gave rise to the greatest mineralization current efficiencies reported so far, up to 1000%, with a low energy consumption of 84 kWh (kg TOC) −1 . The synergy between homogeneous and heterogeneous catalysis, which allowed the efficient dosage of OH and M( OH) at low j , with simultaneous action of high UV power from sunlight justified such a good performance. Analogous apparent rate constants were determined for MeP, EtP and PrP. Slower decays were found with RuO 2 -based anode due to its lower oxidation power. As a result, the MCE was 425% as maximum, but a lower energy consumption of 52 kWh (kg TOC) −1 was needed. Since the role of active chlorine was of minor importance, the formation of toxic, refractory chloroderivatives was minimized. All by-products were transformed into malic, formic and oxalic acids prior to total mineralization.

This study explores the boosted regression trees (BRT), artificial neural network (ANN) and response surface methodology (RSM) to model and optimize the operational variables for the simulation of the Photolytic degradation of Sulfamethoxazole (SMX) and concurrent total organic carbon (TOC) removal, based on the experimental data set. Four candidate variables involving initial pH (2–11), initial SMX concentration (50–200 mg L−1), temperature (15–45 °C) and time (6–120 min) were considered for simultaneous optimization of SMX and TOC degradation. The result revealed that all the three models are statistically considerable as the values of R, R2, adj-R2 are >0.85, thus be deemed to work well in data fitting, prediction, and optimization, nevertheless, the values of R, R2, adj-R2, RMSE, MAE and AAD are far better for ANN and BRT than RSM method. The ∼100% SMX degradation conditions were found to be as follows: treatment time: 25 min, pH: 2.0, temperature: 35 °C and SMX concentration: 50 mg L−1, while the maximum possible removal of TOC under the given conditions was ∼25%. The percentage contribution (PC) of each variable was deduced by ANOVA analysis of proposed quadratic models which indicated that time and pH are important factors than temperature and SMX concentration. The photolytic intermediates and inorganic ions of SMX, were identified and a potential route of transformation was also proposed.

Made available in DSpace on 2018-12-11T17:14:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-10-01 The flow-by electrochemical reactor is generally used in batch mode with extended process time in order to achieve high efficiency in the removal of organic contaminant from aqueous solution. Moreover, the batch mode system is inappropriate for the treatment of wastewater in high volume or as a continuous stream. This paper presents a new operational mode for the electrochemical reactor in which the electrolyte passes over the electrodes just once at a reduced flow rate and with high hydraulic retention time. The concentration of hydrogen peroxide generated in the reactor running in the single-pass flow mode attained 10.2 mg L-1 cm-2 in acid medium, a value similar to that obtained previously with the same type of reactor operating in batch mode. In the single-pass mode, the electrochemical reactor showed high rates of removal of the antibiotic levofloxacin (initial 50 mg L-1) and organic load (initial 130 mg L-1) up to 99 and 86%, respectively, when operated under electro- or photo-Fenton degradation conditions (acid medium with Fe2+ ions; absence or presence of UV irradiation). Degradation of levofloxacin generated high levels of nitrate (up to 4.5 mg L-1) and various by-products that could be identified by liquid chromatography-mass spectrometry. Escola de Engenharia de Lorena Universidade de São Paulo, Estrada Municipal do Campinho sn Instituto de Química de São Carlos Universidade de São Paulo, Av. Trabalhador São-carlense 400 Escola de Engenharia de São Carlos Universidade de São Paulo, Av. Trabalhador São-carlense 400 Inst. Nac. de Tecnologias Alternativas para Deteccao Avaliacao Toxicologica e Remocao de Micropoluentes e Radioativos Instituto de Química Unesp, Caixa Postal 355 Inst. Nac. de Tecnologias Alternativas para Deteccao Avaliacao Toxicologica e Remocao de Micropoluentes e Radioativos Instituto de Química Unesp, Caixa Postal 355

The purpose of the study was to evaluate the degradation of the organophosphate pesticide profenofos in acidic medium using a gas diffusion electrode (GDE) modified with 5.0% cobalt phthalocyanine (CoPc). The degradation of profenofos was based on oxidation by H 2 O 2 electrogenerated in situ , and experiments were performed in the absence or presence of Fe(II) catalyst. Removal of the pesticide by anodic oxidation was minimal (~ 20%), and reached only 36% when H 2 O 2 was electrogenerated in the absence of catalyst. However, in the presence of 0.15 mmol L − 1 FeSO 4 ·7H 2 O (electro-Fenton reaction), profenofos removal attained 91% after 60 min of process time while total organic carbon (TOC) was reduced by 37%. Prolonged electrolysis under similar electro-Fenton conditions showed that 100% profenofos removal could be achieved after 2 h and a 89.9% reduction in TOC could be attained after 4 h. Analysis by gas chromatography–mass spectrometry of the by-products formed during the process revealed the progressive degradation of profenofos to o - and p -benzoquinone, with subsequent rupture of the aromatic ring to form oxalic acid and, ultimately, CO 2 and H 2 O. It is concluded that wastewater treatments involving H 2 O 2 electrogeneration in a CoPc-modified GDE were effective in removing profenofos and TOC from commercial formulations of profenofos.

In this work, the electrolysis of Reactive Blue 19 (RB-19, a toxic textile dye with a high half-life) using a highly non-commercial boron-doped diamond film on titanium substrate (BDD/Ti) was studied. The BDD film with a B/C ratio of 15,000 ppm, a doping level around 10 19 cm −3 and higher content of sp 3 (diamond) than sp 2 (graphite) was produced with high quality and stability. Under appropriate conditions, the electrode promoted complete decolorization of RB-19, together with 99% of TOC removal and a significant decrease in toxicity against V. fischeri . Furthermore, benzene rings, aromatic amines and naphthalene could be removed also during the electrodegradation. The decay in dye concentration followed pseudo-first order kinetics and the values of the apparent rate constant increased with increasing current density applied. In addition, the main intermediates compounds of RB-19 degradation on BDD/Ti based on HPLC–MS analysis were amino-anthraquinone, tautomers keto-enolic, hydroquinone and benzoquinone, benzoic acid, phenol and acid aliphatic, such as oxalic acid. It is concluded that electrochemical oxidation using a BDD/Ti anode represents a satisfactorily method for the removal of RB-19 in aqueous solutions.

Made available in DSpace on 2020-12-12T01:12:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-05-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The present work reports the degradation of the antibiotic ciprofloxacin (CIP) by different advanced oxidative process systems (UV; Anodic Oxidation; H2O2; H2O2/UV; H2O2/Fe2+ and H2O2/UV/Fe2+) in an electrochemical cell using gas diffusion electrode (GDE) for the synthesis of hydrogen peroxide. CIP degradation and mineralization were evaluated by high efficiency liquid chromatography (HPLC) and total organic carbon (TOC) techniques. Of all the systems investigated, the photoelectro-Fenton system presented the best degradation efficiency; this system promoted highly significant mineralization percentages of 54.8% and 84.6% in 90 and 360 min, and relatively lower energy consumption rates of 4110.0 and 9808.2 kWh kg−1 TOC, respectively. In 6 h period of experiment, the main degradation products of ciprofloxacin were identified, and the aliphatic acids obtained helped confirm the rupture of the aromatic ring. The application of the photoelectro-Fenton process with in situ eletroctrogeneration of H2O2 using GDE has proved to be suitably promising for the treatment of organic pollutants. Institute of Chemistry - São Carlos University of São Paulo, P.O. Box,780, CEP-13560-970, São Carlos National Institute of Alternative Technologies for Detection Toxicological Assessment and Removal of Radioactives and Micropollutants (INCT-DATREM) Institute of Chemistry São Paulo State Univeristy - Unesp Lorena School of Engineering University of São Paulo, CEP 12602-810, Lorena National Institute of Alternative Technologies for Detection Toxicological Assessment and Removal of Radioactives and Micropollutants (INCT-DATREM) Institute of Chemistry São Paulo State Univeristy - Unesp FAPESP: #2013/02762-5 FAPESP: #2014/50945-4 FAPESP: #2016/08760-2 FAPESP: #2017/10118-0 CAPES: 001 CNPq: 302874/2017-8 CNPq: 427452/2018-0

The removal of benzophenone-3 (BP-3), a ubiquitous pollutant in municipal wastewater treatment facilities, was optimal by means of a sequential electrocoagulation (EC)/UVA photoelectro-Fenton (PEF) treatment. Overall mineralization was attained upon combination of EC (Fe/Fe cell, 15 mA cm−2, 20 min) with PEF (boron-doped diamond/air-diffusion cell, 33.3 mA cm−2, 720 min), being superior to EC/electro-Fenton (EF) and requiring shorter time than single PEF. In EC, an Al/Al cell yielded the largest removal of BP-3 in a simulated matrix at pH 11.0 due to precipitation of its neutral form caused by a substantial pH drop, with optimum current density of 15 mA cm−2. EC of BP-3-loaded urban wastewater at natural pH was quite effective also with a Fe/Fe cell, being preferred since it provided the required metal catalyst for subsequent treatment. Among the electrochemical advanced oxidation processes tested, PEF was superior to electrochemical oxidation with electrogenerated H2O2 (EO-H2O2) and EF, especially when using the boron-doped diamond instead of a RuO2-based anode, due to the oxidation of generated active chlorine and hydroxyl radicals, along with the photolytic action of UVA irradiation. GC-MS revealed the formation of 14 cyclic products in PEF treatment, two of them being also formed during EC.

Although various processes for the removal of Reactive Black 5 (RB5) dye from textile wastewater have been studied, the degradation pathway of RB5 on boron-doped diamond (BDD) films has not been elucidated. We here report the efficient electro-oxidation of RB5 in aqueous solution using BDD/Ti electrodes and we propose a degradation route based on intermediates and byproducts identified by high performance liquid chromatography-mass spectrometry. BDD films doped with 5000 or 15,000 ppm of B were grown on Ti plates using the hot filament chemical vapor technique to produce electrodes E1 and E2, respectively. Films were evaluated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy before and after several hours of electrolysis and were shown to be of high quality and stability. Total removal of color from RB5 solution was achieved with either electrode by electrolysis at low current density (50 mA cm−2). Total mineralization of the dye solution could be attained with electrode E2 at an applied current density of 100 mA cm−2. Under these conditions, 91% of the chromatographic area associated with RB5 (monitored at 311 nm) was removed, thereby verifying cleavage of the aromatic rings of the dye. Furthermore decolorization of RB5 followed pseudo zero-order kinetics with both electrodes and the apparent rate constant was higher with electrode E2. The results obtained indicate that BDD/Ti is a promising material for the electro-degradation of RB5 since aromatic rings and chromophoric groups were ruptured during electrolysis to generate aliphatic compounds, such as oxalic acid, that can be easily converted into CO2.

This study examined the photo-assisted electrochemical degradation and mineralization of the antibiotic contaminant sulfamethoxazole (SMX). All the experiments were perform using a flow electrolytic cell, in which the influence of the current density (10-60 mA cm

This study examined the photo-assisted electrochemical degradation and mineralization of the antibiotic contaminant sulfamethoxazole (SMX). All the experiments were perform using a flow electrolytic cell, in which the influence of the current density (10–60 mA cm −2 ) and sodium chloride (0.02–0.10 mol L −1 ) in the supporting electrolyte composition was analyzed. The results showed that the total SMX and 50% TOC removal was achieved in the current density range used. As expected, the degradation kinetics presented a pseudo first order behavior and the rate constant increased from 0.05 min −1 to 0.50 min −1 as the current density raised from 10 to 60 mA cm −1 . In addition, the values of the electrical energy per order (E EO ) increased from 0.67 to 1.06 kW/hm −3 order −1 as the current density increased from 10 to 60 mAcm −2 and drop from 8.82 to 0.57 kW/hm −3 order −1 at supporting electrolyte concentration of 0.02–0.1 mol L −1 . The reaction intermediates identified by liquid chromatography–mass spectrometry allowed proposing a mechanism for the degradation. The use of photo assistance in the electrochemical process involved simultaneous reactions, for example, aromatic ring substitutions and hydroxylation. These reactions led to aromatic rings opening that generated simpler organic molecules, making possible the mineralization of the SMX molecule. Probable degradation pathways were proposed and discussed. Comparison of the efficiencies of the photocatalytic, electrochemical (EC) and photo-assisted electrochemical (PAEC) techniques revealed that the combined process showed a synergism for TOC removal.

Amaranth dye is used widely in the processing of paper, textiles, foods, cosmetics, beverages and medicines, and effluents contaminated with this compound are discharged daily into the environment. Recent studies have shown that azo dyes, especially those such as amaranth dye that have been classified as endocrine disruptors, may cause adverse effects to animal and human health. This paper describes the application of electrochemical oxidation (with a boron-doped diamond BDD thin-film anode) coupled with ultrasound sonolysis (20 kHz and 523 W cm−2) to the removal of amaranth dye from dilute alkaline solution. The electrochemical and sonoelectrochemical processes (ECh and SECh, respectively) were carried out at constant current density (10 to 50 mA cm−2) in a single compartment cylindrical cell. Sonolysis was virtually less useful for the decolorization and degradation of amaranth dye, whilst ECh and SECh were more effective in degrading the dye with almost complete removal (90 - 95%) attained after 90 min of experiment at an applied current density of 50 mA cm−2. Degradation of the dye followed pseudo first-order kinetics in both processes, but the rate of reaction was faster with the SECh treatment confirming a synergistic effect between the cavitation process and the electrochemical system. Additionally, at low applied current densities (10 and 25 mA cm−2), SECh was considerably more effective than ECh for the amaranth dye mineralization. Although at 35 and 50 mA cm−2, the two processes showed the respective removal of total organic carbon values: (i) 85% for the ECh and 90% for the SECh at 35 mA cm−2; (ii) 96% for the ECh and 98% for the SECh at 50 mA cm−2. It is concluded that SECh presented the most favorable results for the decontamination of wastewaters containing azo dye compounds.

Methyl paraben is commonly employed as a preservative in pharmaceutical preparations, personal care products and some processed foods. However, the ester constitutes a potential pollutant in aquatic environments and has been classified as an endocrine disruptor. This study describes the degradation of methyl paraben (100 mg L−1 in 0.05 mol L−1 aqueous potassium sulfate at pH 5.7) by means of an electrochemical process (employing a boron-doped diamond anode) either alone or coupled with sonolysis. Electrolyses were performed at 25, 30 and 35 ± 1 °C during 120 min using applied constant current densities of 10.8 and 21.6 mA cm−2. The hybrid sonoelectrochemical processes were conducted under similar conditions with the application of ultrasound at a frequency of 20 kHz and a power intensity of 523 W cm−2. Although mineralization of methyl paraben could be achieved using either process, in comparison with the electrochemical method, the hybrid technique showed a higher mineralization efficiency (around 60 %) with approximately 50 % removal of total organic carbon, thereby confirming the synergistic effect of sonolysis.

aUniversity of Sao Paulo, Sao Carlos Chemistry Institute, Sao Carlos, Sao Paulo, CEP 13566-590, Brazil 5 bUniversity of Sao Paulo, FFCLRP, Department of Chemistry, Ribeirao Preto, Sao Paulo, CEP 14040-901, Brazil 6 7 This study reports the synthesis and characterization of a new ruthenium complex that acts as a molecular catalyst for organic compounds oxidation. The cis-[Ru(BAP)(bpy)(PPh3)(OH2)](ClO4)2 complex, a precursor monomer, was analyzed by UV-Vis and FTIR spectroscopy and used to build new modified electrodes, using carbon rod and carbon felt as substrates. The characterization of these modified electrode surfaces was realized by cyclic voltammetry and the catalytic activity of the films immobilized on the surfaces was tested for the selective oxidation of several organic substrates by heterogeneous electrolysis. The kinetic parameters and yield were better than those obtained by homogeneous catalysis using similar ruthenium complexes. The results allowed to demonstrate the formation of a polymeric film from the ruthenium complex, as well as, to establish the mechanisms for the selective oxidation of the organic species tested. 8 9 10 11 12 13 14 15 © 2014 The Electrochemical Society. [DOI: 10.1149/2.1051410jes] All rights reserved. 16

The production, characterization, and application of boron doped diamond grown on titanium substrates (BDD/Ti) are proposed in a systematic study taking into account the optimized parameters to produce high quality electrodes in a suitable doping level applied in the electrooxidation of the Brilliant Green dye. The process efficiency was analyzed as a function of the BDD doping levels as well as their sp 2 hybridization content in the film structures. A large set of sixteen BDD/Ti samples were applied in the electrooxidation experiments at constant current density of 100 mA cm − 2 , using 100 mg L − 1 of the Brilliant Green dye in K 2 SO 4 0.1 mol L − 1 solution for 300 min. The electrooxidation efficiency in the whole sample set was analyzed by UV/VIS Spectrophotometry and by Total Organic Carbon techniques considering the influence of the electrode characteristics in the degradation process. The results showed that all the electrodes were efficient in the solution discolorization and in the organic compound mineralization. However, BDD/Ti electrode with the lowest sp 2 content associated to the intermediate doping level presented the best results. A mechanist route for the dye degradation was proposed, using the normalized parameters for the best BDD electrode, from high performance liquid chromatography — mass spectroscopy analyses.

Parabens are widely used industrial preservatives, routinely found in wastewater along with major inorganic ions like sulfate and chloride. This work investigates the oxidation ability of three electrochemical processes in tank reactors equipped with an air-diffusion cathode to electrogenerate H2O2 on site, namely electro-oxidation (EO-H2O2), electro-Fenton (EF) and UVA photoelectro-Fenton (PEF), to degrade aqueous solutions of methylparaben (MeP) at pH 3.0. Their performance using boron-doped diamond (BDD), Pt or two kinds of dimensionally stable anodes (DSA®) has been compared from the analysis of mineralization profiles and decay kinetics in the presence of sulfate and/or chloride ions. The use of BDD ensured the overall mineralization in all three processes according to the sequence: PEF > EF > EO-H2O2, thanks to the contribution of BDD( OH), OH and UVA light. Pt and DSA® became an interesting alternative in PEF, with slower organic matter removal but similar final mineralization percentages, being much less powerful than BDD in EO-H2O2. The presence of Cl− was beneficial in the latter process, due to the formation of active chlorine as an additional oxidant that caused a much faster decay of MeP. Conversely, it became significantly detrimental in EF due to the partial destruction of H2O2 and OH in the bulk by active chlorine and Cl−, respectively. The oxidation power of PEF was so high that similar fast, complex decay kinetics was found in all media regardless of the anode, although the mineralization was decelerated owing to the accumulation of chlorinated by-products. GC-MS and HPLC analysis allowed the identification of up to seven aromatic MeP derivatives in sulfate + chloride mixtures, including three non-chlorinated compounds also found in pure sulfate medium. These molecules were gradually transformed into oxalic acid, along with four chlorinated aliphatic carboxylic acids in Cl−-containing media.

A comparative study was carried out of sonochemical (SCh), electrochemical (ECh) and sonoelectrochemical (SECh) strategies for the degradation of the fungicide thiram in dilute aqueous solution. The SCh and SECh studies were performed using a sonicator equipped with an 11 mm titanium-alloy probe and operated at 20 kHz with a power intensity of 523 W cm(-2). In the ECh and SECh investigations, galvanostatic electrolyses were implemented using a single compartment electrochemical cell with a boron-doped diamond electrode as anode and applied current densities in the range 10-50 mA cm(-2). For these processes, the decrease in concentration of thiram was monitored by high performance liquid chromatographic (HPLC) analysis and values of current efficiency and energy consumption were determined. The results showed that the rate of degradation of thiram and the amount of energy consumed were directly proportional to the applied current density, while current efficiency was inversely related to current density. The kinetics of thiram degradation followed a pseudo first order model with apparent rate constants in the region of 10(-3)min(-1). Thiram in aqueous solution was subjected to "exhaustive" degradation by ECh and SECh processes for 5h at applied current densities of 35 mA cm(-2) and the intermediates/byproducts so-formed were identified by HPLC-mass spectrometry. Mechanisms of the degradation reactions have been proposed on the basis of the results obtained.

This work describes the application of substituted magnetite nanoparticles, Fe 3− x Cu x O 4 (0 ≤ x ≤ 0.25), as heterogeneous catalysts for the electro-Fenton process in alkaline medium (KOH, pH 13.4) using an uncatalyzed gas diffusion electrode based on Printex carbon. The, Fe 3− x Cu x O 4 (0 ≤ x ≤ 0.25) nanoparticles were synthesized by a co-precipitation method and were characterized by neutron activation analysis (NAA), X-ray diffraction (XRD), transmission electron microscopy (TEM), N 2 -physisorption analysis and X-ray photoelectron spectroscopy (XPS). Cu 2+ /Cu + cations were successfully substituted in the octahedral site of Fe 3 O 4 causing changes in the catalytic activity of the NPs. The electrodegradation of amaranth food dye was performed at −1.1 V ( vs. Ag/AgCl) for 90 min under constant flow of O 2 in the GDE. The dye solution samples were analyzed by UV–vis spectrophotometry, high performance liquid chromatography (HPLC) and total organic carbon (TOC). The maximum color removal was 98%, the degradation was 98%, the mineralization was 70% and the specific energy consumption 483.0 kWh kg −1 for Fe 3− x Cu x O 4 with x = 0.25. The kinetics of the process was of pseudo-first order. The consumed H 2 O 2 increased with increasing value of x in the spinel of Fe 3− x Cu x O 4 (0 ≤ x ≤ 0.25). No residues of soluble Fe 2+ and Cu 2+ ions were detected at the end of electrolysis. XRD analysis of the Fe 2.75 Cu 0.25 O 4 (limit of the solid solution) confirmed the stability of the NPs after the Fenton test.

The electrochemical oxidation of aqueous solution containing methyl paraben (100 mg L-1) in Na2SO4 (0.05 mol L-1) was performed in a one compartment cell using a BDD (boron-doped diamond) anode. Electrolyses were carried out at different current densities (25 at 100 mA cm-2) and the results indicated that the process is supported by mass transport. The kinetic analysis based on methyl paraben concentration monitored during electrolysis shows that the concentration decay has a pseudo first-order behavior.

Glassy carbon electrodes were coated with the film poly-(p-allyl ether benzenesulfonic acid) by an anodic procedure. Nickel, platinum, and palladium ions were introduced into the film by ion exchange of H+ with the corresponding salts. These ions were catalytically reduced to their corresponding metals using the known electroless reducing agent sodium hypophosphite. Scanning electron microcopy and energy dispersive X-ray spectroscopy were carried out to demonstrate the occurrence of the catalytic process. To compare this method with another one carried out in our laboratory, the electrocatalytic reduction of H+ was studied using the same modified electrodes. A suggested mechanism for the catalysis is proposed.

This work describes the preparation of a new modified electrode containing a ruthenium complex (cis-aquadimethylbipyridyltriphenylphosphineruthenium II), bonded to a stable polyphenol film. This modified electrode promotes the fast electrocatalytic oxidation of safrol (5-allyl-benzo[1,3]dioxole) and isosafrol (5-propenyl-benzo[1,3]dioxole), giving two interesting products benzo[1,3]dioxole-5-carbaldehyde (piperonal) and 3-benzo[1,3]dioxol-5-yl-propenal respectively, with good yields. The electrode preparation can be carried out at a potential range which does not interfere on the anchored electroactive ruthenium complex, but it allows for the phenol oxidation to occur and therefore polymerize forming the polyphenol film. The catalytic character of this modified electrode is showed by its high turnover numbers. The procedure to isolate the products is very simple.

The appearance of pharmaceutical compounds and their bioactive transformation products in aquatic environments is becoming an issue of increasing concern. In this study, the electrochemical oxidation of the widely used antibiotic sulfamethoxazole (SMX) was investigated using a commercial mixed oxide anode (Ti/Ru0.3Ti0.7O2) and a single compartment filter press-type flow reactor. The kinetics of SMX degradation was determined as a function of electrolyte composition, applied current density, and initial pH. Almost complete (98 %) degradation of SMX could be achieved within 30 min of electrolysis in 0.1 mol L−1 NaCl solution at pH 3 with applied current densities ≥20 mA cm−2. Nine major intermediates of the reaction were identified by LC-ESI-Q-TOF-MS (e.g., C6H9NO2S (m/z = 179), C6H4NOCl (m/z = 141), and C6H6O2 (m/z = 110)). The degradation followed various routes involving cleavage of the oxazole and benzene rings by hydroxyl and/or chlorine radicals, processes that could occur before or after rupture of the N-S bond, followed by oxidation of the remaining moieties. Analysis of the total organic carbon content revealed that the antibiotic was partially mineralized under the conditions employed and some inorganic ions, including NO3 − and SO4 2−, could be identified. The results presented herein demonstrate the efficacy of the electrochemical process using a Ti/Ru0.3Ti0.7O2 anode for the remediation of wastewater containing the antibiotic SMX.

Amaranth dye is an organic compound largely used in the food and beverage industries with potential toxicity effects on humans. It can be found as a pollutant species in aquatic environments and has been classified as an endocrine disruptor. This study describes amaranth degradation upon ultrasonication associated with an electrochemical system that uses a boron-doped diamond anode BDD, defined as a sonoelectrochemical process. Ninety-minute electrolyses were performed using current densities in the 10–50 mA cm−2 range, and the concentration decay, pH, energy and current efficiencies, as well as the discoloration rate were evaluated. The amaranth concentration decayed as a function of electrolysis time and the reactions obeyed pseudo first-order kinetics, with an apparent constant rate between 10−1 and 10−3 min−1. The electrochemical and sonoelectrochemical processes at 35 mA cm−2 yielded TOC removal values between 92.1% and 95.1% respectively, after 90 min. Current efficiency values obtained for both processes were 18.2% and 23.6%. Exhaustive 5 h electrolysis was performed and the degradation products were identified by HPLC–MS. A mechanism for the degradation of amaranth was proposed based on an analysis of the aromatic and aliphatic intermediates.

Parabens have been widely used in different industries and can be found in health and personal care products. They are esters of p -hydroxy-benzoic acid associated with breast tumors and classified as endocrine disruptors. This study describes the galvanostatic electrochemical oxidation of methyl paraben (MePa) on a boron-doped diamond anode using current densities in the 1.35 to 21.6 mA cm −2 range. The degradation process can be controlled by either charge transfer or mass transport, according to the experimental conditions and rate of mineralization of MePa increased by the current density. The concentration variation as a function of electrolysis time showed that the degradation kinetics follows a pseudo first-order law. A mechanism for the MePa degradation based on reactive intermediates determined by gas chromatography mass spectrometry (GC-MS) is also proposed.

The aim of the present study was to investigate the electrochemical degradation of dipyrone in a single compartment electrochemical cell equipped with a gas diffusion electrode (GDE) modified with cobalt (II) phthalocyanine. Degradations were performed under conditions of anodic oxidation (GDE pressurized with N2) and under conditions promoting the electrogeneration of H2O2 (GDE pressurized with O2) both in the absence and presence of 1 mmol FeSO4.7H2O (electro-Fenton conditions). The efficiency of the electro-Fenton process was satisfactory at all studied potentials, and achieved a maximum reduction of 67% in electrolyte absorbance at 262 nm after 90 min electrolysis at −0.7 V (vs. Ag/AgCl). The reduction in dipyrone concentration attained 95% after 90 min of reaction with electrogenerated H2O2 in the absence or presence of Fe2+ ions at all potentials except −0.5 V (vs. Ag/AgCl). The removal of total organic carbon (TOC) was most efficient under electro-Fenton conditions with a decrease of 54.4% in organic load attained at -0.9 V (vs. Ag/AgCl) and energy consumption (EC) of 270 kWh per kg of TOC removed. © 2014 The Electrochemical Society. [DOI: 10.1149/2.0091414jes] All rights reserved.

Electrodegradation of the azo dye amaranth using a modified gas diffusion electrode (MGDE), prepared with Printex 6L carbon black and 5.0% cobalt (II) phthalocyanine, has been investigated with the aim of developing an efficient method of treating contaminated effluent derived from the food and beverage processing industries. Hydrogen peroxide was electrogenerated at a potential of −0.7 V ( vs . Ag/AgCl) under a constant flow of O 2 , and electrodegradations were performed in the absence or presence of Fe 2+ or Fe 3+ (electro-Fenton conditions). The removal of color and total organic carbon (TOC) from the dye solution was observed under all reaction conditions, although process efficiency was improved markedly by the addition of Fe ions. Following 90 min of electrolysis, maximal values for decolorization (79.3%) and mineralization (67.3%) were achieved in the presence of 0.15 mM Fe 2+ , and energy consumption (370.0 kW h kg −1 per kg of TOC removed) was minimal under these conditions. Concentrations of residual Fe in treated electrolytes were either below the permissible limit or could be rendered so by conventional treatment. It is concluded that the electro-Fenton reaction with Fe 2+ and a MGDE represents a viable process for the degradation of amaranth in aqueous medium.

A comparative study using different mass proportions of WO3/C (1%, 5%, 10% and 15%) for H2O2 electrogeneration and subsequent phenol degradation was performed. To include the influence of the carbon substrate and the preparation methods, all synthesis parameters were evaluated. The WO3/C materials were prepared by a modified polymeric precursor method (PPM) and the sol–gel method (SGM) on Vulcan XC 72R and Printex L6 carbon supports, verifying the most efficient metal/carbon proportion. The materials were physically characterized by X-ray diffraction (XRD) and by X-ray photoelectron spectroscopy (XPS) techniques. The XRD and the XPS techniques identified just one phase containing WO3 and elevated oxygen concentration on carbon with the presence of WO3. The oxygen reduction reaction (ORR), studied by the rotating ring-disk electrode technique, showed that WO3/C material with the lowest tungsten content (1% WO3/C), supported on Vulcan XC 72R and prepared by SGM, was the most promising electrocatalyst for H2O2 electrogeneration. This material was then analyzed using a gas diffusion electrode (GDE) and 585 mg L−1 of H2O2 was produced in acid media. This GDE was employed as a working electrode in an electrochemical cell to promote phenol degradation by an advanced oxidative process. The most efficient method applied was the photo-electro-Fenton; this method allowed for 65% degradation and 11% mineralization of phenol during a 2-h period. Following 12 h of exhaustive electrolysis using the photo-electro-Fenton method, the total degradation of phenol was observed after 4 h and the mineralization of phenol approached 75% after 12 h.

Drug residues are unregulated pollutants and are frequently found in the aquatic environment. Due to their extensive use, presence in the aquatic environment and their potential for impacts on wildlife and humans, it is becoming an important environmental issue. The present study evaluates the photo-assisted electrochemical treatment of sulfamethoxazole (SMX), an antibiotic used in the prevention and treatment of human and animal diseases. The experiments were carried out in a photo illuminated flow cell reactor and the effects of current density and concentration of sodium chloride in the supporting electrolyte were determined. The Drug could be removed completely at all current densities while TOC abatement was appreciable during the process. The process followed pseudo-first order kinetics and values of electrical energy-per-order were dependent on current density and sodium chloride concentration. Different reaction intermediates were separated and identified by liquid chromatography coupled with mass spectrometry (LC-MS), thereby providing an insight into the mechanistic details of the degradation pathway. The photo-assisted electrochemical degradation proceeded through competitive reactions such as chlorination, hydroxylation and substitution on the aromatic ring, while further ring opening gave rise to more simple organic compounds and, ultimately, the mineralization of SMX. The possible degradation route were also proposed and discussed. Figure 1

Neste trabalho os complexos cis- [Ru(BAF)(bpy)(PPh3)(OH2)](ClO4)2 (monômero B) e cis-[Ru(dmbpy)2(PPh3)(OH2)](OPh)2 (monômero C) foram sintetizados e caracterizados através de métodos espectroscópicos e eletroquímicos, sendo utilizados na construção de novos eletrodos modificados EMs e aplicados na eletrooxidação de substratos orgânicos. A preparação destes EMs consistiu no recobrimento da superfície de eletrodos de feltro de carbono e de bastões de grafite pelos filmes poliméricos ancorados ao rutênio. Os intervalos de potencial aplicados para a polimerização dos complexos foram àqueles correspondentes, respectivamente, aos potenciais de polimerização do contra-íon difenolato e do ligante azóico contendo o grupamento fenol. A atividade catalítica destes EMs foi investigada através de um estudo cinético, através de eletrooxidações heterogêneas acompanhadas por UV/Vis de diversos compostos orgânicos como: safrol, isosafrol, álcool benzílico, fenil etil álcool, etil benzeno, tolueno, benzaldeído, ciclo hexen-2-ol, demonstrando que os EMs podem ser utilizados como catalisadores em reações de eletrooxidações com rendimentos satisfatórios. In this work the complexes cis-[Ru(BAF)(bpy)(PPh3)(OH2)](ClO4)2 (B monomer) and cis-[Ru(dmbpy)2(PPh3)(OH2)](OPh)2 (C monomer) were synthesized and characterized by spectroscopic and electrochemical methods, and they were utilized in construction of new modified electrodes (MEs) and applied in electrooxidation of organic substrates. The preparation of these new MEs was done by coating the surfaces of carbon felt and carbon rod electrodes by polymeric films where the ruthenium complexes were anchored. The potential range applied to accomplish the polimerization of the complexes corresponds to the potencial ranges of diphenol anion and azoic ligand with the phenolic group, respectively. The catalytic activity of these MEs was studied by kinetic methodology monitoring the heterogeneous electroxidations by UV/Vis of some organic substrates like: safrol, isosafrol, benzylic alcohol, phenil ethyl alcohol, ethyl benzene, toluene, cycle-hexen-2-ol, showing that these EMs can be utilized as catalyst in electrooxidations reactions with goods yields.

This work presents two new modified carbon electrodes which were prepared via the polymerization of a phenolic moiety previously functionalized with azo groups (bipyridine and 2-methoxypyridine) as key structures to anchor the desired ligands. The syntheses of BAP (4-([2,2’]-bipyridinyl-4-ylazo)-phenol) and PAPmethoxy (5-(4-hidroxyphenylazo) pyridin-2-methoxy) were simple to perform, gave good yields and the monomers were easily electropolymerized resulting in chemically and mechanically stable modified electrodes. The PAP-methoxy ME formed stable complexes with Cd, Cu and Pb in aqueous media at open circuit and produced well defined redox peaks, showing good potential for future analytical applications. The BAP monomer was used to produce a ruthenium complex (BAP-Ru) which was electropolymerized from +0.50 to +0.75V (vs. Ag/AgCl) to leave the ruthenium available to act as a catalyst. The BAP-Ru ME was able to oxidize a variety of organic substrates with good selectivity. The yields obtained were either similar to, or better than, those obtained by homogeneous catalysis using a similar ruthenium catalyst or when this type of catalyst is supported in a carbon paste electrode. Este trabalho apresenta dois novos eletrodos de grafite modificados que foram preparados via polimerização da função fenólica, previamente funcionalizada por grupos azo (bipiridina e 2-metoxipiridina), que atuam como estruturas chaves para a ancoragem de ligantes de interesse. As sínteses dos monômeros BAP (4-([2,2’]bipiridinil-4-ilazo)-fenol) e PAPmetóxi (5-(4-hidroxifenilazo)piridin-2-metóxi) foram simples, deram bons rendimentos e os monômeros foram facilmente eletropolimerizados, levando à formação de eletrodos modificados (EM) química e mecanicamente estáveis. Em solução aquosa e em circuito aberto, o EM PAP-metóxi formou complexos estáveis com Cd, Cu e Pb, produzindo picos redox bem definidos, demonstrando o grande potencial deste eletrodo para futuras aplicações analíticas. O monômero BAP foi utilizado para produzir um complexo de rutênio (BAP-Ru) que foi eletropolimerizado entre +0.50 e +0.75V (vs. Ag/AgCl), permitindo que o rutênio permanecesse disponível para atuar como catalisador. O EM BAP-Ru oxidou seletivamente uma variedade de substratos orgânicos dando produtos com rendimentos próximos ou melhores que aqueles obtidos por catálise homogênea com complexos de rutênio similares, ou quando este tipo de catalisador é impregnado em pasta de carbono.

not Available.