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The aim of this work was to evaluate three carbon materials as anodes in microbial fuel cells (MFCs), clarifying their influence on the generation of electricity and on the treatability of winery wastewater, a highly organic-loaded waste. The electrode materials tested were carbon felt, carbon cloth and carbon paper and they were used at the same time as anode and cathode in the tests. The MFC equipped with carbon felt reached the highest voltage and power (72 mV and 420 mW m−2, respectively), while the lowest values were observed when carbon paper was used as electrode (0.2 mV and 8.37·10−6 mW m−2, respectively). Chemical oxygen demand (COD) removal from the wastewater was observed to depend on the electrode material, as well. When carbon felt was used, the MFC showed the highest average organic matter consumption rate (650 mg COD L−1 d−1), whereas by using carbon paper the rate decreased to 270 mg COD L−1 d−1. Therefore, both electricity generation and organic matter removal are strongly related not to the chemical composition of the electrode (which was graphite carbon in the three electrodes), but to its surface features and, consequently, to the amount of biomass adhered to the electrode surface.

BACKGROUND Microbial fuel cells (MFCs) can treat agro-industrial wastewater, but only a few studies have reported the treatment of winery waste and much work is needed in order to develop this interesting application of MFC technology, in particular in evaluating how the unfavorable COD/N and COD/P ratios may affect the MFC performance. In this work, a dual chamber MFC was used to treat real effluents from wine processing factories. RESULTS The MFC was not efficient in terms of COD removal, even when nutrients concentration was increased and daily removals which oscillated around 1000 mg L-1 d-1 were observed during the complete experimental period, with COD removals around 17%. Increases in the phosphorus and nitrogen concentrations positively influenced the production of electricity. By increasing the concentration of phosphorus and nitrogen, Coulombic efficiency was increased from 2% to almost 15%, and maximum power density from 105 to 465 mW m-2. CONCLUSIONS Results demonstrate that electricity can be produced efficiently and that the unbalanced nutrients/COD ratio is a major challenge in the treatment of winery wastewater, in spite of the very high organic load contained in this type of wastewater. © 2015 Society of Chemical Industry, ANTECEDENTES Las celdas de combustible microbianas (MFC) pueden tratar aguas residuales agroindustriales, pero solo unos pocos estudios han informado el tratamiento de residuos de bodegas y se necesita mucho trabajo para desarrollar esta interesante aplicación de la tecnología MFC, en particular en la evaluación de cómo la DQO desfavorable / Las relaciones N y COD / P pueden afectar el rendimiento del MFC. En este trabajo, se utilizó un MFC de doble cámara para tratar efluentes reales de las fábricas de procesamiento de vino. RESULTADOS El MFC no fue eficiente en términos de remoción de DQO, aun cuando se incrementó la concentración de nutrientes y se observaron remociones diarias que oscilaron alrededor de 1000 mg L -1 d -1 durante todo el período experimental, con remociones de DQO alrededor del 17%. Los aumentos en las concentraciones de fósforo y nitrógeno influyeron positivamente en la producción de electricidad. Al aumentar la concentración de fósforo y nitrógeno, la eficiencia de Coulombic se incrementó del 2% a casi el 15% y la densidad de potencia máxima de 105 a 465 mW m -2 . CONCLUSIONES Los resultados demuestran que la electricidad se puede producir de manera eficiente y que la relación desequilibrada nutrientes / DQO es un gran desafío en el tratamiento de las aguas residuales de bodegas, a pesar de la altísima carga orgánica contenida en este tipo de aguas residuales. © 2015 Sociedad de la Industria Química

It is investigated in the present contribution the oscillatory co-electrodeposition of CuSn on a polycrystalline gold surface in the presence of Triton X-100 surfactant and citric acid as additive, in acidic media. The experiments were conducted under potentiostatic control and the system dynamics characterized in terms of the morphology and stability of the current oscillations. Besides modulations in the frequency and amplitude of the current oscillations, several patterned states were observed, including relaxation-like and mixed mode oscillations. The oscillations were found to be very robust and some time series presented regular motions up to about two hours.

There is presently much interest in the clean and efficient generation of energy by proton exchange membrane fuel cells (PEMFC), using hydrogen as fuel. The generation of hydrogen by the reforming of other fuels, anaerobic fermentation of residual waters and other methods, often produce contaminants that affect the performance of the cell. In this work, the effect of gaseous SO2 and NO2 on the performance of a H2/O2 single PEMFC is studied. The results show that SO2 decreases irreversibly the performance of the cell under operating conditions, while NO2 has a milder effect that allows the recovery of the system.

This paper describes in detail a technique employed to grow quasi-spherical single crystals of noble metals for electrochemical applications, using platinum as an example. The metal beads were formed by melting the extremity of a wire in an oxygen / butane flame. X-ray techniques were used to check the crystallization and to determine the orientation of the crystals. Treatment with a pure hydrogen flame followed by a cooling procedure in a hydrogen / argon atmosphere were used for conditioning the well-defined platinum single crystal surfaces. Finally, electrochemical characterization of the Pt(111), Pt(110) and Pt(100) surfaces was done in diluted sulfuric acid solution in the hydrogen adsorption / desorption potential region.