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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

Oxygen reduction reaction (ORR) is an important reaction with applications in advanced oxidative processes through in situ hydrogen peroxide electrogeneration. Oxygen can be reduced either to hydrogen peroxide via two-electron pathway or in a competitive way to water via four-electron pathway. This study shows the application of Printex L6 carbon modified with niobium/molybdenum or niobium/palladium oxides for H2O2 generation in K2SO4 0.1 mol L−1 (pH 2), where the modified carbon contributed to an increase in electroconductivity compared to unmodified carbon. The catalysts were prepared by the polymeric precursor method and were analyzed by x-ray absorption near edge structure (XANES), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) which showed the presence of orthorhombic Nb2O5 and MoO3 and tetragonal PdO independent phases. Also, the data obtained from x-ray fluorescence (FRX) and transmission electron microscopy (TEM) showed particle size of about 5 nm for the modified Printex L6 carbon compared to 25–30 nm for the unmodified Printex L6 carbon in an almost homogeneous distribution on the carbon surface. Based on the electrochemical analyses, the values obtained for H2O2 selectivity were 77, 77 and 88% for 5% Nb50Mo50/C, 5% Nb90Pd10/C, and 5% Nb95Pd05/C, respectively, compared to 89% for unmodified Printex L6 carbon. The materials investigated presented potential shifts of 110, 420 and 340 mV for 5% Nb50Mo50/C, 5% Nb90Pd10/C and 5% Nb95Pd05/C, respectively, compared to Printex L6 carbon at a determined current density.

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.

A new electrode for the photoelectrochemical removal of 17β-estradiol from water using ruthenium oxide nanoparticles supported on reduced graphene oxide is proposed in this study. The morphology, microstructure and the electrochemical performance of the material were characterized using HRTEM, XRD and Raman spectroscopy. The characterization showed the formation of reduced graphene oxide from a micro-wave assisted hydrothermal method with a particle size of 5.0 nm + 2.4 nm. The electrochemical measurements point to a high performance of the electrode in the presence of a white light source. The hormone removal efficiency in water containing 50 μmol L−1 of 17β-estradiol was evaluated using chronoamperometry at +1.0 V and the process was monitored using liquid chromatography. The reaction is pseudo first order with the removal of 92.2% of 17β-estradiol after 60 min of photoelectrocatalytic treatment.

Direct electrochemical generation of hydrogen peroxide in aqueous medium represents an attractive method for the production of the oxidizing agent. This paper describes the development of electrocatalysts comprising Printex L6 carbon black containing 0 to 10% (w/w) of copper or cobalt phthalocyanine (CuPc and CoPc, respectively) as modifier. Formation of H2O2 by the ORR in acidic medium was investigated by linear voltammetry using a rotating ring-disc electrode, whose glassy carbon disc contained a microporous layer of the catalyst. Incorporation of CuPc into Printex decreased the current efficiency for H2O2 formation [i(H2O2)%] from 75.4% for unmodified Printex to a minimum of 53.3% when 10% of the modifier was present. However, i(H2O2)% increased when CoPc was employed as modifier, and a maximum value of 92.3% was attained with Printex containing 1.0% CoPc. Moreover, a shift of +340 mV (relative to unmodified Printex) was observed in the overpotential required for the generation of H2O2 when 10% of CoPc was present. SECM demonstrated that, at a potential of -0.2 V, Printex with 10% CoPc produced larger amounts of H2O2 compared with unmodified Printex. It is concluded that the use of the CoPc modifier is promising for the electrogeneration of H2O2 on a large scale.

This paper reports the use of different proportions of vanadium nanostructured electrocatalysts for H 2 O 2 electrogeneration. A comparative study using different mass proportions of vanadium (1%, 6%, 12%, 15% and 20%) was performed to produce H 2 O 2 . The V/C materials were prepared by a modified polymeric precursor method (PPM) and characterized by X-ray diffraction and transmission electron microscopy (TEM) analysis. XRD results identified different phases comprising V 2 O 5 and VO 2 while TEM micrographs show the vanadium nanoparticles in the range of 1–3 nm. The rotating ring–disk electrode (RRDE) technique was used to evaluate the kinetics of the oxygen reduction reaction (ORR). The results showed that the 12% V/C prepared by the PPM was the best composite among those investigated for the production of H 2 O 2 in a 1 mol L −1 NaOH electrolyte solution because this electrocatalyst exhibited a H 2 O 2 conversion efficiency of 68%. The ring current obtained with 12% V/C was greater than the obtained with Vulcan carbon, which was used as a reference material for H 2 O 2 production and exhibited an efficiency of 31%. After the study with the RRDE, gas-diffusion electrodes (GDEs) containing the catalyst were used to evaluate the amount of H 2 O 2 produced during exhaustive electrolysis. On the basis of these results, the 12% V/C GDE produced 620 mg L −1 of H 2 O 2 in alkaline media, whereas the Vulcan carbon GDE produced only 369 mg L −1 at the same potential. In acidic media, the 12% V/C GDE produced 107 mg L −1 of H 2 O 2 , whereas Vulcan carbon produced only 72 mg L −1 at the same potential, indicating the better activity of V/C for H 2 O 2 electrogeneration. The 12% V/C is composed primarily of the V 2 O 5 phase, which shows acidic character that can increase the acidity of the surface, providing greater hydrophilicity and, consequently, greater activity toward the ORR via two-electron transference.

Hydrogen peroxide (H2O2) is a versatile oxidizing agent that is synthesized commercially by the reduction of oxygen in organic medium. Electrochemical technology employing a modified gas diffusion electrode (MGDE) offers a viable alternative for the industrial-scale synthesis of the oxidant. Addition of 1% (w/w) of tert-butyl-anthraquinone (TBAQ) to carbon black deposited in the form of a microporous layer onto the disk of a rotating ring-disk electrode produced an increase in the ring current, which is directly related to H2O2 formation, and presented an efficiency of H2O2 generation of 89.6% compared with 76.6% for carbon black alone. No significant changes were detected in the number of electrons transferred in the presence of the catalyst suggesting an electrochemical/chemical mechanism for H2O2 formation. Analogous improvements in the generation of H2O2 were obtained with MGDEs comprising TBAQ on carbon black. The highest concentrations of H2O2 (301 mg L−1) were produced at the fastest rate (5.9 mg L−1 min−1) with the lowest energy consumption (6.0 kWh kg−1) when a potential of −1.0 V vs SCE was applied to a MGDE containing 1.0% of TBAQ on carbon black. It is concluded that the application of MGDEs comprising TBAQ on carbon black support offers considerable advantages in the electrogeneration of H2O2.

Hydrogen peroxide (H 2 O 2 ) is a commonly used oxidant with a wide variety of applications in, for example, organic synthesis and wastewater treatment. This paper describes the development of catalysts for the electrogeneration of H 2 O 2 in acidic medium using gas diffusion electrodes (GDE). Initial experiments were performed using rotating ring-disk electrodes modified with microporous layers of Printex 6L carbon containing various amounts of cobalt (II) phthalocyanine (CoPc) in order to evaluate catalytic activities. The results showed that the current efficiency for the formation of H 2 O 2 increased from 69.7% for Printex 6L carbon without catalyst to 81.5% when using Printex 6L carbon with CoPc, and this was accompanied by a decrease in the number of electrons involved in the oxygen reduction reaction from 2.6 to 2.3. Based on these findings, modified GDEs were constructed containing 3.0, 5.0 and 10.0% of CoPc on Printex 6L carbon. The concentration of H 2 O 2 that formed after 90 min electrolysis with the GDE modified with Printex 6L carbon alone was 176 mg L −1 , while the GDE with 5.0% CoPc on carbon produced 331 mg L −1 of H 2 O 2 , i.e. an increase in yield of 89.1% relative to Printex 6L carbon. Additionally, using GDE s modified with CoPc on carbon, the potential at which H 2 O 2 formation attained its maximum value shifted to less negative values in comparison with electrodes without catalyst. It is concluded that CoPc is an appropriate catalyst for efficient electrogeneration of H 2 O 2 .

A study of the electrochemical degradation of profenofos in a flow reactor with electrodes comprising boron-doped diamond films deposited on titanium substrate (BDD/Ti) as anodes has been performed. The BDD films were produced at growth times of 7 and 24 h with similar B/C ratios corresponding to acceptor concentrations of around 10 20 atoms cm − 3 . The morphological and structural characteristics of the BDD/Ti electrodes were evaluated by scanning electron microscopy and Raman scattering spectroscopy. Degradation experiments were carried out with applied current densities in the range 10 to 200 mA cm − 2 and flow rates of 50 and 300 L h − 1 . The rates of degradation of profenofos were evaluated by high performance liquid chromatography and variations in total organic carbon (TOC) were monitored during the electrochemical process in order to determine the level of mineralization of organic compounds present in the electrolyte. Under the best conditions (anode comprising a BDD film deposited on titanium for 7 h and reactor operating at a flow rate of 300 L h − 1 ) more than 95% of the profenofos was degraded and approximately 87% of TOC was removed within 120 min of reaction time.

This paper describes the effect of the composition of the oxide films on the properties of electrodes Ti/MxTiySnzO2 (M = Ir or Ru) prepared by the polymeric precursor method. XRD studies showed that the anodes are formed by solid solutions. The electrodes containing IrO2 exhibit lower activity for the oxygen evolution reaction. The doping of the electrode surface with SnO2 improves the catalytic properties of the anodes. However, it should be held in appropriate compositions, because the change in the atomic ratio of this element shows a marked effect on the stability of the oxides. Electrode Ti/Ir0.2Ti0.3Sn0.5O2 has lower lifetime, i.e. 6 hours. The 20% decrease in the stoichiometric amount of SnO2 increases the time to a value above 70 hours, as observed for Ti/Ir0.3Ti0.4Sn0.3O2. Electrode Ti/Ru0.3Ti0.4Sn0.3O2 shows lifetime of 11 hours; therefore IrO2 is more stable than RuO2 under the conditions investigated. These results suggest that electrode Ti/Ir0.3Ti0.4Sn0.3O2 is promising for different applications, such as water electrolysis, capacitors and organic electrosynthesis.

Made available in DSpace on 2018-11-27T13:40:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-05-05 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Highly efficient H2O2 electrogeneration is required in the Advanced Oxidation Process for organic wastewater treatment. However, the development of more efficient catalytic particles used in gas diffusion electrodes (GDEs) to enable the oxygen reduction reaction through two-electron transfer is still of great importance. The performance of the Ta2O5 nanoparticles on carbon black in catalyzing the ORR was evaluated using rotating ring-disk electrode. The current efficiency for H2O2 electrogeneration on Ta2O5/C catalyst is 83.2% whereas carbon black exhibits 65.3%. GDEs were constructed using carbon black either unmodified or modified with Ta2O5 nanoparticles. The modified GDE produces 27.9 mg L-1 of H2O2, while the unmodified GDE generates 19.1 mg L-1 of H2O2. Furthermore, the energy consumption for the H2O2 electrogeneration is lower in modified than in unmodified GDE (15.0 kWh vs. 18.8 kWh). The high performance of the GDE (Ta2O5/C) renders it a viable alternative cathode in the electrochemical treatment of wastewaters. (C) 2016 Elsevier B.V. All rights reserved. Univ Sao Paulo, Inst Quim Sao Carlos, Ave Trabalhador Sao Carlene 400, BR-13566590 Sao Carlos, SP, Brazil Univ Estadual Paulista, Inst Quim, Rua Prof Francisco Degni 55, BR-14800060 Araraquara, SP, Brazil Univ Estadual Campinas, Fac Engn Mecan, Rua Mendeleyev 200, BR-13083860 Campinas, SP, Brazil Univ Estadual Paulista, Inst Quim, Rua Prof Francisco Degni 55, BR-14800060 Araraquara, SP, Brazil CNPq: 163689/2015-6 CNPq: 160507/2011-1 CNPq: 143345/2011-7 CNPq: 470079/2013-4 FAPESP: 2011/14314-1

A comparative study using different proportions of CeO 2 /C (4%, 9% and 13% CeO 2 ) was performed to produce H 2 O 2 , a reagent used in the oxidation of organic pollutants and in electro-Fenton reactions for the production of the hydroxyl radical (OH ), a strong oxidant agent used in the electrochemical treatment of aqueous wastewater. The CeO 2 /C materials were prepared by a modified polymeric precursor method (PPM). X-ray diffraction analysis of the CeO 2 /C prepared by the PPM identified two phases, CeO 2 and CeO 2− x . The average size of the crystallites in these materials was close to 7 nm. The kinetics of the oxygen reduction reaction (ORR) were evaluated by the rotating ring-disk electrode technique. The results showed that the 4% CeO 2 /C prepared by the PPM was the best composite for the production of H 2 O 2 in a 1 mol L −1 NaOH electrolyte solution. For this material, the number of electrons transferred and the H 2 O 2 percentage efficiency were 3.1 and 44%, respectively. The ring-current of the 4% CeO 2 /C was higher than that of Vulcan carbon, the reference material for H 2 O 2 production, which produced 41% H 2 O 2 and transferred 3.1 electrons per molecule of oxygen. The overpotential for this reaction on the ceria-based catalyst was substantially lower (approximately 200 mV), demonstrating the higher catalytic performance of this material. Gas diffusion electrodes (GDE) containing the catalyst were used to evaluate the real amount of H 2 O 2 produced during exhaustive electrolysis. The 4% CeO 2 /C GDE produced 871 mg L −1 of H 2 O 2 , whereas the Vulcan carbon GDE produced a maximum amount of only 407 mg L −1 . Thus, the 4% CeO 2 /C electrocatalyst prepared by the PPM is a promising material for H 2 O 2 electrogeneration in alkaline media.

This paper reports on an evaluation of the viability of electrochemical technology as a clean alternative for the manufacture of chemicals and raw materials for the chemical industry. In the present work, a (TiO2/RuO2)/PTFE gas diffusion electrode (GDE) was designed for use in the electrochemical conversion of ethylene into ethylene glycol under conditions of simultaneous oxygen evolution. The GDE was produced by pressing and sintering TiO2(0,7)/RuO2(0,3) powder and PTFE and used in the electrosynthesis of ethylene glycol. In the experiments, ethylene was inserted in the reaction medium by the GDE and electrosynthesis was carried out in 0.1 mol L−1 Na2SO4 supporting electrolyte. A solution of 330 mg L−1 of ethylene glycol was obtained in 20 min with the application of 0.7 mA cm−2. During the experiments, the current efficiency was 70% and energy consumption was

The investigation reported in this paper aims the recycling of greenhouse gases and their conversion into fuels or useful chemicals. In the present work, a (TiO2/RuO2)/PTFE gas diffusion electrode (GDE) was designed and characterized to be used in the electrochemical conversion of methane into methanol in conditions of simultaneous oxygen evolution. The GDE was obtained by pressing and sintering TiO2(0.7)/RuO2(0.3) powder and PTFE and used for the electrosynthesis of methanol from methane. In the experiments, methane was inserted into the reaction medium by the GDE and electrosynthesis was carried out in 0.1 mol L−1 Na2SO4 supporting electrolyte. Controlled potential experiments showed that methanol concentration increased with applied potential, reaching 220 mg L−1 cm2, at 2.2 V vs. a calomel reference electrode and current efficiency for methanol formation was 30%. Mass spectrometry data also indicated the formation of formaldehyde and formic acid, the latter at a similar rate as that of methanol.

The study of the electrochemical degradation of the ranitidine was developed using an electrochemical reactor with a gas diffusion electrode (GDE) as cathode. The electrolysis experiments was performed at constant current (1 < A < 10) and flow rate of 200 L h-1. The process of drug degradation, chemical/electrochemical and electro-Fenton ways, using electrochemical reactor showed best efficiency at current values of > 4 A. The process reached a production of 630 mg L-1 of the H2O2 at 7 A. The ranitidine concentrations was reduced in 99.9% (HPLC) and chemical oxygen demand (COD) was reduced in 86.7% by electro-Fenton.

This paper reports an investigation on the performance of a catalyzed H2O2 electrogeneration process using a modified oxygen-fed graphite/PTFE electrodes in which the redox catalyst was incorporated into the graphitic mass. The organic redox catalyst chosen for the modification was 2-ethylanthraquinone (EAQ). The H2O2 electrogeneration rate was optimized relative to potential and catalyst concentration. Hydrogen peroxide formation rate on oxygen-fed graphite/PTFE was greatly improved by the presence of the organic redox catalyst and the overpotential for oxygen reduction was shifted more positive. During electrolysis, hydrogen peroxide electrogeneration reaction showed a pseudo-zero-order kinetics and apparent rate constants increased with EAQ concentration. For the electrodes containing 10% of EAQ, apparent rate constants were 30% higher at a potential 400 mV more positive when compared to the performance of a non catalyzed electrode.

The increasing occurrence of antibiotics and their metabolites in surface and ground waters is causing a significant impact on the environment and needing of developing novel treatments for the complete removal of such contaminants. This paper presents the study of the electrogeneration of hydrogen peroxide (H2O2) in acidic medium and the degradation of the analgesic dipyrone in an electrochemical flow reactor using a gas diffusion electrode (GDE) modified with 5.0% cobalt (II) phthalocyanine (CoPc) and pressurized with O2. The highest yield of H2O2 (133 mg L-1) was achieved after 90 min of electrolysis at an applied potential of -2.1 V (vs. Pt//Ag/AgCl/KCl s) and the best results for degradation of dipyrone were obtained under electro-Fenton conditions, where the total organic carbon (TOC) was reduced 62.8% after 90 min of reaction and 49.1 kW h of energy was consumed per kg of dipyrone degraded. A crescente ocorrência de antibióticos e seus metabólitos estão cada vez maiores em águas superficiais e subterrâneas, causando impactos significativos no meio ambiente e necessitando de desenvolvimento de novos tratamentos para a remoção completa de tais contaminantes. Este trabalho apresenta o estudo da eletrogeração de peróxido de hidrogênio (H2O2) em meio ácido e a degradação do analgésico dipirona em um reator de fluxo eletroquímico usando um eletrodo de difusão gasosa (GDE) modificado com 5,0% ftalocianina de cobalto (II) (CoPc) e pressurizado com O2. A maior produção de H2O2 alcançada foi de 133 mg L-1 a um potencial aplicado de -2,1 V (vs. Pt//Ag/AgCl/KCl s) e os melhores resultados para a degradação da dipirona foram obtidos sob condições eletro-Fenton, em que o carbono orgânico total (TOC) foi reduzido 62,8% após 90 min de reação e 49,1 kW h de energia foi consumida por kg de dipirona degradada.

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.

Hydrogen peroxide (H2O2) is commonly produced by redox reactions involving organic compounds in organic medium, but such processes present several limitations including the need to extract and concentrate a highly active product. Hydrogen peroxide can be generated in situ by the electrochemical reduction of oxygen in aqueous medium, and the process is particularly efficient when gas diffusion electrodes (GDEs) are employed. A key challenge in the development of such electrodes is the choice of the catalytic particles. This paper describes the evaluation of iron (II) phthalocyanine as a modifier of pigment carbon black used in the construction of GDEs. After 90 min of electrolysis at constant potential, a GDE containing 5% of modifier generated 240 mg L−1 of H2O2 (rate constant 7 mg L−1 min−1; energy consumption 165 kW h kg−1 H2O2) while the unmodified GDE produced only 175 mg L−1 of H2O2 (3 mg L−1 min−1; 300 kW h kg−1 H2O2) under the same experimental conditions.

This work studied the degradation of dipyrone, via electrochemical processes and via electro-Fenton reaction using a 4% CeO 2 /C gas diffusion electrode (GDE) prepared via modified polymeric precursor method. This material was used to electrochemically generate H 2 O 2 through oxygen reduction. The mean crystallite sizes estimated by the Scherrer equation for 4% CeO 2 /C were 4 nm for CeO 2− x (0 4 4) and 5 nm for CeO 2 (1 1 1) while using transmission electron microscopy (TEM) the mean nanoparticle size was 5.4 nm. X-ray photoelectron spectroscopy (XPS) measurements revealed nearly equal concentrations of Ce(III) and Ce(IV) species on carbon, which contained high oxygenated acid species like CO and O C O. Electrochemical degradation using Vulcan XC 72R carbon showed that the dipyrone was not removed during the two hour electrolysis in all applied potentials by electro-degradation. Besides, when the Fenton process was employed the degradation was much similar when using cerium catalysts but the mineralization reaches just to 50% at −1.1 V. However, using the CeO 2 /C GDE, in 20 min all of the dipyrone was degraded with 26% mineralization at −1.3 V and when the Fenton process was employed, all of the dipyrone was removed after 5 min with 57% mineralization at −1.1 V. Relative to Vulcan XC72R, ceria acts as an oxygen buffer leading to an increase in the local oxygen concentration, facilitating H 2 O 2 formation and consequently improving the dipyrone degradation

Methane fed TiO 2 /RuO 2 /PTFE gas diffusion electrodes (GDEs) have been used for the electrosynthesis of methanol in 0.1 mol L −1 of Na 2 SO 4 supporting electrolyte. By-products such as formaldehyde and formic acid are usually also formed during electrolyses, with the latter formed at a similar rate as that of methanol. In this study, V 2 O 5 was added to the composition of the GDE to improve its selectivity for methanol. TiO 2 /RuO 2 /V 2 O 5 powder hot-pressed with PTFE resulted in a GDE suitable for oxidative electrosynthesis with simultaneous oxygen evolution. By feeding the TiO 2 /RuO 2 /V 2 O 5 /PTFE GDE with methane, it was possible to enhance its selectivity for methanol at low values of current density. Furthermore, the formation of formic acid and formaldehyde was suppressed, allowing for higher current efficiencies. The addition of 5.6% of V 2 O 5 increased the electrode's current efficiency to 57% at 2.0 V, which is 2-fold higher than the efficiency achieved in the absence of vanadium oxide.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:48:50Z No. of bitstreams: 1 S0100-40422010000500015.pdf: 225987 bytes, checksum: 17059c73bf3cbb7bcb56fcdb80128502 (MD5) Made available in DSpace on 2013-08-22T18:48:50Z (GMT). No. of bitstreams: 1 S0100-40422010000500015.pdf: 225987 bytes, checksum: 17059c73bf3cbb7bcb56fcdb80128502 (MD5) Previous issue date: 2010-01-01 Made available in DSpace on 2013-09-30T19:09:28Z (GMT). No. of bitstreams: 2 S0100-40422010000500015.pdf: 225987 bytes, checksum: 17059c73bf3cbb7bcb56fcdb80128502 (MD5) S0100-40422010000500015.pdf.txt: 28770 bytes, checksum: 5d0518dfb6a65cd08ec2b5cb95afe162 (MD5) Previous issue date: 2010-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:19:46Z No. of bitstreams: 2 S0100-40422010000500015.pdf: 225987 bytes, checksum: 17059c73bf3cbb7bcb56fcdb80128502 (MD5) S0100-40422010000500015.pdf.txt: 28770 bytes, checksum: 5d0518dfb6a65cd08ec2b5cb95afe162 (MD5) Made available in DSpace on 2014-05-20T14:19:46Z (GMT). No. of bitstreams: 2 S0100-40422010000500015.pdf: 225987 bytes, checksum: 17059c73bf3cbb7bcb56fcdb80128502 (MD5) S0100-40422010000500015.pdf.txt: 28770 bytes, checksum: 5d0518dfb6a65cd08ec2b5cb95afe162 (MD5) Previous issue date: 2010-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) This paper reports a study of electrochemical degradation of the chloramphenicol antibiotic in aqueous medium using a flow-by reactor with DSA® anode. The process efficiency was monitored by chloramphenicol concentration analysis with liquid chromatography (HPLC) during the experiments. Analysis of Total Organic Carbon (TOC) was performed to estimate the degradation degree and Ion Chromatography (IC) was performed to determinate inorganic ions formed during the eletrochemical degradation process. In electrochemical flow-by reactor, 52% of chloramphenicol was degraded, with 12% TOC reduction. IC analysis showed the production of chloride ions (25 mg L-1), nitrate ions (6 mg L-1) and nitrite ions (4.5 mg L-1). Universidade São Francisco Universidade Estadual de Campinas Faculdade de Engenharia Mecânica Departamento de Engenharia de Materiais Universidade Estadual Paulista Instituto de Química de Araraquara Departamento de Química Analítica Universidade de São Paulo Instituto de Química de São Carlos Departamento de Química e Física Molecular Universidade Estadual Paulista Instituto de Química de Araraquara Departamento de Química Analítica