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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

The present study investigates the modification of carbon black with ruthenium and niobium oxides and the application of the modified carbon material for the electrogeneration of hydrogen peroxide via oxygen reduction reaction. The modified carbon materials were characterized electrochemically using the porous microlayer technique on rotating ring-disc electrode. The modification of amorphous carbon black with 5.0% Ru05Nb95O (5.0% Ru05Nb95O/C) contributed to the enhancement of selectivity toward H2O2 electrogeneration, with current efficiency of 84.6% and a shift in potential of − 0.300 V. The most efficient material (5.0% Ru05Nb95O/C) was characterized by X-ray absorption spectroscopy, X-ray fluorescence and scanning electron microscopy. The application of gas diffusion electrodes for H2O2 generation in acid medium yielded 281.6 mg L−1 of H2O2 in 120 min of experiment at current density of 100 mA cm−2. The concentration of H2O2 electrogenerated on the modified carbon material was 33.6% higher compared to the concentration electrogenerated on the unmodified carbon material (210.8 mg L−1) under the same experimental conditions.

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.

This paper reports the synthesis of a new class of catalysts based on niobium using Filter Cake (FC) as precursor, which is more affordable economically than other niobium sources commonly used. FC is obtained before the necessary purification to obtain niobic acid (Nb2O5∙nH2O), making the catalyst synthesis process less costly. Its modification by hydrothermal treatment in the presence of different agents (oxalic acid or hydrogen peroxide) allowed the obtention of nanostructured materials in the form of rods or spheres with larger BET area, crystallinity and acidity than the precursor. Their catalytic potential were evaluated in fructose dehydration reaction in aqueous media, aiming the obtention of 5-hydroxymethylfurfural (5-HMF). The production of furan compounds from sugars has become a process of great interest in recent years because it is related to the search for more sustainable sources of energy, since carbohydrates are the predominant part of biomass. In optimum conditions, it was possible to obtain 22% yield of 5-HMF in aqueous medium and 47% yield of 5-HMF using DMSO as solvent.

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

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 .

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

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.

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 reports the development of GDE for electrogeneration of H2O2 and their application in the degradation process of Reactive Blue 19 dye. GDE produced by carbon black with 20% polytetrafluoroethylene generated up to 500 mg L-1 of H2O2 through the electrolysis of acidic medium at -0.8 V vs Ag/AgCl. Reactive Blue 19 dye was degraded most efficiently with H2O2 electrogenerated in the presence of Fe(II) ions, leading to removal of 95% of the original color and 39% of TOC at -0.8 V vs Ag/AgCl.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:48:58Z No. of bitstreams: 1 S0100-40422012001000014.pdf: 1031323 bytes, checksum: b7c91b774a0eee006b480caaed4ad41d (MD5) Made available in DSpace on 2013-08-22T18:48:58Z (GMT). No. of bitstreams: 1 S0100-40422012001000014.pdf: 1031323 bytes, checksum: b7c91b774a0eee006b480caaed4ad41d (MD5) Previous issue date: 2012-01-01 Made available in DSpace on 2013-09-30T19:09:17Z (GMT). No. of bitstreams: 2 S0100-40422012001000014.pdf: 1031323 bytes, checksum: b7c91b774a0eee006b480caaed4ad41d (MD5) S0100-40422012001000014.pdf.txt: 36386 bytes, checksum: ec9c04d462d60b6970fe89f08fc36800 (MD5) Previous issue date: 2012-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:19:38Z No. of bitstreams: 2 S0100-40422012001000014.pdf: 1031323 bytes, checksum: b7c91b774a0eee006b480caaed4ad41d (MD5) S0100-40422012001000014.pdf.txt: 36386 bytes, checksum: ec9c04d462d60b6970fe89f08fc36800 (MD5) Made available in DSpace on 2014-05-20T14:19:38Z (GMT). No. of bitstreams: 2 S0100-40422012001000014.pdf: 1031323 bytes, checksum: b7c91b774a0eee006b480caaed4ad41d (MD5) S0100-40422012001000014.pdf.txt: 36386 bytes, checksum: ec9c04d462d60b6970fe89f08fc36800 (MD5) Previous issue date: 2012-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) This work reports the development of GDE for electrogeneration of H2O2 and their application in the degradation process of Reactive Blue 19 dye. GDE produced by carbon black with 20% polytetrafluoroethylene generated up to 500 mg L-1 of H2O2 through the electrolysis of acidic medium at -0.8 V vs Ag/AgCl. Reactive Blue 19 dye was degraded most efficiently with H2O2 electrogenerated in the presence of Fe(II) ions, leading to removal of 95% of the original color and 39% of TOC at -0.8 V vs Ag/AgCl. Universidade de São Paulo Instituto de Química de São Carlos Departamento de Química e Física Molecula Universidade Estadual Paulista Instituto de Química de Araraquara Departamento de Química Analítica 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