Search

Highly efficient H 2 O 2 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 Ta 2 O 5 nanoparticles on carbon black in catalyzing the ORR was evaluated using rotating ring-disk electrode. The current efficiency for H 2 O 2 electrogeneration on Ta 2 O 5 /C catalyst is 83.2% whereas carbon black exhibits 65.3%. GDEs were constructed using carbon black either unmodified or modified with Ta 2 O 5 nanoparticles. The modified GDE produces 27.9 mg L −1 of H 2 O 2 , while the unmodified GDE generates 19.1 mg L −1 of H 2 O 2 . Furthermore, the energy consumption for the H 2 O 2 electrogeneration is lower in modified than in unmodified GDE (15.0 kW h vs. 18.8 kW h). The high performance of the GDE (Ta 2 O 5 /C) renders it a viable alternative cathode in the electrochemical treatment of wastewaters. [ABSTRACT FROM AUTHOR]

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 FeS04.7H20 (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. [ABSTRACT FROM AUTHOR]

The increasing use of synthetic dyes in commercial food processing has heightened the need for more effective methods of treating industrial wastewaters prior to discharge into the environment. The present report describes the efficient electrodegradation of tartrazine dye in dilute aqueous solution using the electro-Fenton process with Fe (II) or Fe (III) as catalyst and a gas diffusion electrode modified with 5.0% cobalt phthalocyanine. The highest level of color removal (98.4% in 90 min) from solution and the most rapid decay in concentration (kapp 6.0 x 10-2 min-1) of tartrazine dye were achieved in the presence of 0.15 mmol Fe (II). Under these conditions, the amount of total organic carbon (TOC) removed in 90 min was maximal (75%) while energy consumed was minimal (219.0 kWh kg-1 TOC removed). The amount of residual iron was slightly higher than that allowed by the Brazilian authorities for dissolved Fe in wastewaters, indicating that further treatment of the effluent would be necessary. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen peroxide (H2O2) 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 H2O2 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 H2O2 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 H2O2 that formed after 90min electrolysis with the GDE modified with Printex 6L carbon alone was 176mgL−1, while the GDE with 5.0% CoPc on carbon produced 331mgL−1 of H2O2, 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 H2O2 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 H2O2. [Copyright &y& Elsevier]

The present work reports the degradation of the antibiotic ciprofloxacin (CIP) by different advanced oxidative process systems (UV; Anodic Oxidation; H 2 O 2 ; H 2 O 2 /UV; H 2 O 2 /Fe2+ and H 2 O 2 /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 H 2 O 2 using GDE has proved to be suitably promising for the treatment of organic pollutants. • The highest hydrogen peroxide production was obtained 755 mg L-1 with 84.5 kWh of energy consumed by 1 kg of H 2 O 2. • The synergism between H2O2/Fe2+/UV provided the greatest removal of organic matter. • CIP degradation indicated molecular oxidation and aliphatic acid formation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effluents containing azo food dye amaranth (AM) represent an environmental hazard. [•] Electrodegradation of AM achieved using a modified gas diffusion electrode (MGDE). [•] Decolorization and mineralization of AM was maximal in presence of 0.15mM Fe2+. [•] Energy consumption for removal of total organic carbon was minimal with 0.15mM Fe2+. [ABSTRACT FROM AUTHOR]

Highlights: [•] The iron (II) phthalocyanine was used as modifier in the GDE for H2O2 generation. [•] At 90min the GDE generated 240mgL−1 of H2O2. [•] The most generation consumption 165kWh for kg of H2O2. [ABSTRACT FROM AUTHOR]

Abstract: 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 (301mgL−1) were produced at the fastest rate (5.9mgL−1 min−1) with the lowest energy consumption (6.0kWhkg−1) when a potential of −1.0V 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. [Copyright &y& Elsevier]