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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 Fe 2+ ions; absence or presence of UV irradiation). Degradation of levofloxacin generated high levels of nitrate (up to 4.5 mg L −1) and various byproducts that could be identified by liquid chromatography-mass spectrometry.

In this work, materials based on core-shell W@Au type structures were found to have promise for use as electrocatalysts on the in-situ production of H 2 O 2 by means of the oxygen reduction reaction (ORR). We describe herein the synthesis and characterization of these materials and then present a study of electrocatalytic activity towards ORR by the electrogeneration of H 2 O 2 employing these materials supported on Vulcan XC-72R carbon corresponding to 1 and 2 wt% loading. The use of W@Au/C materials led to higher activity compared to pure carbon and commercial Pt/C, and the optimal load is 1%, which presented the highest ring current for the ORR using the rotating ring-disk electrode technique. Exhaustive electrolysis using a W@Au/C 1% gas diffusion electrode (GDE) was employed to verify the real amount of H 2 O 2 electrogenerated comparing with a Vulcan XC-72R GDE. We verified that the W@Au/C 1% material is able to generate 50% more H 2 O 2 than carbon. These results can be explained based on synergistic interactions presented by the W@Au/C 1% material and also by both conductivity and hydrophilicity differences provided by the nanostructures supported on carbon.

In this work, the electrolysis, photoelectrolysis and sonoelectrolysis with diamond electrodes of amoxicillin (AMX) and ampicillin (AMP) solutions were studied in the context of the search for technologies capable of removing antibiotics from liquid wastes. Single-irradiation processes (sonolysis and photolysis) were also evaluated for comparison. Results showed that AMX and AMP are completely degraded and mineralized by electrolysis in both chloride and sulfate media, although the efficiency is higher in the presence of chloride. The effect of the current density on mineralization efficiency is not relevant and this may be related to the role of mediated oxidation. Irradiation by ultraviolet light or ultrasound (US) waves does not produce a synergistic effect on the mineralization of AMX and AMP solutions. This indicates that the massive formation of radicals during the combined processes can favor their recombination to form stable and less reactive species.

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RESUMO:Este trabalho objetivou avaliar, via fracionamento físico, a associação do carbono orgânico (CO) com frações granulométricas de solos de campos de murundus localizados na bacia hidrográfica do Rio Guaporé, sudoeste do Estado de Mato Grosso. As coletas das amostras de solo foram realizadas entre setembro e novembro em três diferentes áreas: pastagem nativa em uso, pastagem cultivada e área nativa sem uso. Em cada área foram abertas minitrincheiras de 0,50 m × 0,50 m × 0,40 m e coletadas amostras deformadas e indeformadas nas profundidades de 0,0-0,10, 0,10-0,20 e 0,20-0,30 m, três repetições em delineamento inteiramente casualizado. Foram determinados o teor de CO, o carbono particulado (COP), associado à fração areia e o carbono organo-mineral (COM), associado às frações argila + silte. Não foi verificado diferença entre os ambientes avaliados para as variáveis analisadas nas diferentes profundidades. Os maiores teores de COM foram observados na camada de 0,0-0,10 m, em todas as áreas. Conclui-se que o uso de pastagens naturais e a implantação de pastagens cultivadas, até o momento, não alteraram os teores de carbono do solo bem como suas associações com as frações granulométricas.Palavras-Chave: áreas úmidas, uso da terra, matéria orgânica particulada Abstract -This study aimed to evaluate, by physical fractionation, the association of organic carbon (OC) with granulometric fractions of soils of fields of murundus located at the Guaporé River hydrographic basin, southwest of the State of Mato Grosso. The sampling of soil were carried out between september and november 2011 in three different areas: native pastures in use, cultivated pastures and native areas without use. In each area were open minitrenches of 0,50 m × 0,50 m × 0,40 m and collected disturbed and undisturbed samples at the depths of 0,0-0,10, 0,10-0,20 and 0,20-0,30 m in three replications in completely randomized design. Were determined the carbon content (CO) and particulate carbon (COP), associated with the sand fraction and the organo-mineral carbon (COM), associated with argil + silt fractions. Was not observed difference between the environments evaluated for the variables evaluated in different depth. The highest levels of COM were observed at the depth of 0,0-0,10 m in all areas. It is concluded that the use of native pastures and cultivated pastures, until now, did not alter the contents of soil carbon as well as their associations with the granulometric fractions.