Study of electrocrystallization of Ni and Ni-P on platinum ultramicroelectrode

This work describes a comparative study of the electrocrystallization of Ni and Ni-P on Pt ultramicroelectrodes using chronoamperometric measurements. It was possible to confirm that in all cases a progressive nucleation was the predominant mechanism. Moreover, the application of the Atomistic Theory to the experimental rate of nuclei formation showed that the number of atoms in the critical nucleus was zero, except for Ni-P on Pt at low overpotentials were a value of one was observed. Furthermore, the physical characterisation of the different deposits on Pt by atomic force microscopy allowed observing the coalescence of the hemispherical nuclei of Ni and Ni-P at t max thus confirming the results obtained from the current-time analysis.CNP

Biotecnología ambiental

The various industrial sectors, as well as livestock and agricultural activities, are increasing the production of inputs to meet the demand of the worldwide demographic explosion, making a challenge the clean maintenance of water, soil, and air. Therefore, the search for solutions for a pollutant-free environment without compromising economic development has become extremely important. Thereby, biotechnological studies in order to solve environmental issues have been gaining extensive attention through the coupling of technology procedures to biological systems as sustainable solutions to remediate contaminated areas. In this sense, this review covers topics such as the role of Omics era in microbial environmental biotechnology for pollution control as well as the microbial fuel cell use in energy production. Moreover, phytoremediation and the perspective of applying chemical methods are approached as environmentally friendly tools for the pollutant control to improve remediation processes.Los diversos sectores industriales, así como las actividades ganaderas y agrícolas, están aumentando la producción de insumos para satisfacer la demanda de la explosión demográfica mundial, lo cual dificulta el mantenimiento limpio del agua, el suelo y el aire. Por lo tanto, la búsqueda de soluciones para un medio ambiente libre de contaminantes sin comprometer el desarrollo económico se ha vuelto extremadamente importante. De este modo, los estudios biotecnológicos para resolver problemas ambientales han recibido una gran atención a través del acoplamiento de procedimientos tecnológicos a sistemas biológicos como soluciones sostenibles para remediar áreas contaminadas. En este sentido, esta revisión cubre temas como el papel de la era Ómica en la biotecnología ambiental microbiana para el control de la contaminación, así como el uso de celdas de combustible microbianas en la producción de energía. Además, la fitorremediación y la perspectiva de aplicar métodos químicos se abordan como herramientas ecológicas para el control de contaminantes y mejorar los procesos de remediación

Pt–Sn/C catalysts prepared by sodium borohydride reduction for alcohol oxidation in fuel cells: Effect of the precursor addition order

A series of Pt–Sn/C catalysts used as anodes during ethanol oxidation are synthesized by a deposition process using NaBH4 as the reducing agent. The order in which the precursors are added affects the electrocatalytic activity and physical-chemical characteristics of the bimetallic catalysts, where the Pt–Sn catalyst prepared by co-precipitation of both metals functions best below a potential of 0.5 V and the catalyst prepared by sequential deposition of Sn and Pt (drying after Sn addition) is most active above a potential of 0.5 V. The electrochemical behavior of catalysts during ethanol oxidation in an acidic medium are characterized and monitored in a half-cell test at room temperature by cyclic voltammetry, chronoamperometry and anode potentiostatic polarization. Catalyst structure and chemical composition are investigated by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). This behavior presented for best Pt–Sn catalyst can be attributed to the so-called bifunctional mechanism and to the electronic interaction between Pt and Sn.The authors thank the Brazilian National Council of Technological and Scientific Development-CNPq (grants: 303630/2012-4, 402243/2012-9 and 310282/2013-6) for the scholarships and financial support for this work

Testing the role of electrode materials on the electro-Fenton and photoelectro-Fenton degradation of clopyralid

This work studies the effect of the anode and cathode materials on the degradation of the herbicide clopyralid. Different electrochemical advanced oxidation processes (EAOPs), including electrochemical oxidation with electrogenerated hydrogen peroxide (EO-H2O2), electro-Fenton (EF), and photoelectro-Fenton (PEF) were carried out. The first experiments were focused on the effect of the cathode, where the use of the hydrophobic carbon felt modified by the deposition of carbon black & PTFE mixture (MCF) improves the H2O2 production in comparison to a conventional carbon felt (CF), regardless of the anode material employed. On the other hand, a laser-made Ti/Ru0.3Ti0.7O2 mixed metal oxide (MMO) and a commercial boron-doped diamond (BDD) were compared as anodes. Results obtained point out that the MMO anode promotes the accumulation of this oxidant (H2O2) in bulk. Once characterized by the production of hydrogen peroxide, the second part of this study focused on the degradation of clopyralid with the MCF cathode with different EAOPs. Results demonstrate that clopyralid fastly degrades in the sequence EO-H2O2 < EF < PEF, and almost complete mineralization occurs for EF and PEF employing MMO or BDD as the anode. Synergy effect study shows that irradiation of 9 W UVC produces a positive synergistic effect of 81.7% and 41.55% (for the PEF-MMO and PEF-BDD, respectively), ascribed to the additional removal of aromatic intermediates by the UVC and the activation of H2O2. At the end of the treatment, mineralization of the herbicide was attained at 1.22 kW h (g−1 TOC). Finally, considering the lower cost of the prepared MMO, these findings demonstrate the potentiality of using modified carbon felt combined with the laser-made Ti/Ru0.3Ti0.7O2 anode for the treatment of polluted waters

Photoelectrolysis of clopyralid wastes with a novel laser-prepared MMO-RuO2TiO2 anode

This paper studies the applicability of a novel laser-prepared mixed metal oxide (MMO-RuO2TiO2) anode in the photoelectrochemical degradation of clopyralid, a toxic and biorefractory herbicide. Results are compared to those obtained using the well-known boron-doped diamond (BDD) anode and demonstrate that, although the electrolysis with diamond is more effective than that obtained with the new electrode, the irradiation of UVC light makes the novel MMO material more effective in chloride media. It was explained in terms of the homolysis of hypochlorous acid/hypochlorite to form chloride and hydroxyl radicals. Photoelectrochemical degradation with MMO produced a marked synergistic effect in TOC removal, especially in the presence of chloride ions. On the contrary, for the BDD anode, at the tested conditions, antagonisms were found in both sulfate and chloride media. These important synergisms allows finding conditions in which the novel anode can be competitive with the BDD

Biodegradability improvement of clopyralid wastes through electrolysis using different diamond anodes

The use of boron-doped (BDDs) anodes for efficient removal of complex organic molecules, such as organochlorine compounds, is well stated in the literature. However, the role of the different characteristics of this anode on the transformation of these type of contaminants into more biodegradable molecules is a topic of interest that need to be clarified when aimed an efficient combination of an electrochemical system as a previous step to biological treatment. In this work, improvement in the biodegradability of synthetic wastes polluted with clopyralid, as an organochlorine model compound, is studied after electrolysis with different BDDs in the presence of the two most common supporting electrolytes (containing sulfate or chloride ions). For that, clopyralid removal, mineralization, aromatics intermediates, short-chain carboxylic acids, and inorganic ions were monitored. Improved results were found in sulfate media for BDD with 200 ppm, capable of removing 88.7% of contaminants and 85% of TOC, resulting in an improvement in biodegradability of almost 7-fold compared to the initial sample. These findings point out that lower doping levels are preferable when coupling studied technologies

Methanol Electro-Oxidation on Carbon-Supported PtRu Nanowires

One of the key objectives in fuel cell technology is to improve the alcohol oxidation efficiency of Pt-based catalysts. A series of carbon-supported PtRu nanowires with different concentrations of Pt and Ru were prepared for application in methanol oxidation in acid media. The physicochemical properties and electrocatalytic activity of these catalysts during methanol oxidation are function on their structure, morphology and composition. A Pt60Ru40/C catalyst shows the best behaviour towards methanol electro-oxidation allowing decrease the onset potential approximately 0.2 V respect to others PtRu/C synthesised nanowires. The structural modification of Pt by Ru and synergetic character of RuPt are main factors that could contribute to reduction of energy necessary for electro-oxidation process. The Pt and PtRu nanowires have different sizes and distribution on the substrate. The average crystallite sizes, found by XRD, are in the 4.6–5.9 nm range and the lattice parameter is between 0.3903–0.3908 nm. Small differences with the values of the Pt/C catalyst were found. The XPS results show a prevailing presence of metallic Pt and Ru4+ species.The authors thank to CNPq (grants: 304419/2015-0, 402243/2012-9, 400443/2013-9, 407274/2013-8 and 310282/2013-6), CAPES and FAPITEC for the scholarships and financial support

Understanding the electrolytic generation of sulfate and chlorine oxidative species with different boron-doped diamond anodes

The electrochemical generation of several oxidative species was studied at the surfaces of five commercial boron-doped diamond anodes with different doping levels (100–8000 ppm). These insights can open the possibility of tailoring anodes for a more efficient application in environmental remediation processes. All materials evaluated were characterized by linear sweep voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy, contact angle, and scanning electron microscopy, as well as by bulk electrolysis. As a result, it was confirmed that the boron doping level influences the physical and electrochemical properties of the electrodes, indicating distinct behavior of the electrodes on the production of chlorine and sulfate oxidative species. The higher the boron doping, the lower is the crystallite size, and the higher is the conductivity, the hydrophilic behavior, and the electron-transfer activity. Voltammetric characterization demonstrates that low boron doping favors the formation of hydroxyl radicals, while high doping levels favor the direct electrochemical oxidation of sulfate or chloride. Moreover, when operating at high overpotentials in bulk electrolysis (typical conditions in environmental applications), the formation of chlorine and sulfate oxidative species is favored at low boron doping levels. This behavior is attributed to the very efficient mediated formation of these oxidants from the hydroxyl radicals, whose production is promoted with these electrodes at those conditions. It means that only operating at much softer conditions, the unique direct generation of hydroxyl oxidant occurs, opening a way for the potential prevention of perchlorate formation during disinfection by using highly boron-doped diamond anodes

Outstanding performance of the microwave-made MMO-Ti/RuO2IrO2 anode on the removal of antimicrobial activity of Penicillin G by photoelectrolysis

This paper studies the applicability of a novel microwave-prepared mixed metal oxide (MMO-Ti/RuO2IrO2) anode in the electrolysis and photo-electrolysis of synthetic urine intensified with Penicillin G. Results are compared with those obtained using boron-doped diamond (BDD) as the anode. In general, electrolysis with both anodes are effective in terms of penicillin removal, and the combination with UV radiation shows a clear synergistic effect on the degradation of Penicillin G: 420% and 355% using MMO and BDD, respectively. The outstanding performance of the MMO-Ti/RuO2IrO2 anode is demonstrated by the decrease in toxicity and the reduction of the antibiotic effect on the urine observed during photo-electrolysis. Notably, photo-electrolysis using the MMO-Ti/RuO2IrO2 anode generates solutions with almost zero residual toxicity and without antibiotic effect, with lower specific energy consumption than using BDD anode. The remarkable performance of the microwaves-prepared MMO-Ti/RuO2IrO2 coatings makes them very promising for being used in the electrochemical treatment of sanitary wastes.Este artículo estudia la aplicabilidad de un novedoso ánodo de óxido metálico mixto (MMO-Ti/RuO 2 IrO 2 ) preparado con microondas en la electrólisis y fotoelectrólisis de orina sintética intensificada con penicilina G. Los resultados se comparan con los obtenidos usando diamante (BDD) como ánodo. En general, la electrólisis con ambos ánodos es efectiva en términos de eliminación de penicilina, y la combinación con radiación UV muestra un claro efecto sinérgico en la degradación de Penicilina G: 420% y 355% usando MMO y BDD, respectivamente. El excelente rendimiento del MMO-Ti/RuO 2 IrO 2ánodo se demuestra por la disminución de la toxicidad y la reducción del efecto antibiótico en la orina observado durante la fotoelectrólisis. En particular, la fotoelectrólisis utilizando el ánodo MMO-Ti/RuO 2 IrO 2 genera soluciones con una toxicidad residual casi nula y sin efecto antibiótico, con un consumo de energía específico menor que utilizando el ánodo BDD. El notable rendimiento de los recubrimientos MMO-Ti/RuO 2 IrO 2 preparados con microondas los hace muy prometedores para su uso en el tratamiento electroquímico de desechos sanitarios

Influence of the doping level of boron-doped diamond anodes on the removal of penicillin G from urine matrixes

The objective of this study is to understand the influence of the characteristics of boron-doped diamond anodes on the degradation of Penicillin G contained in urine. Therefore, five commercial BDD anodes with different boron doping levels (100 ppm - 8000 ppm) were studied. These electrodes were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and electrolysis. The boron doping was found to correlate well with the electrochemical properties of the electrodes, and results indicate a different behavior in drug degradation. The improvement in the toxicity and the reduction of the antibiotic effect of urine were the most innovative inputs monitored. For this, the concentration of Penicillin G, the toxicity toward Vibrio fisheri, and the antibiotic effect in Enterococcus faecalis were monitored. The best results were found for the BDD with a boron content of 200 ppm, capable of removing 100% of the antibiotic, reducing toxicity by 90%, and eradicating the antibiotic effect. These results indicate that low doping levels are more efficient for urine removal by anodic oxidation