Correlación del potencial óxido reducción y la población bacteriana durante el estudio de biolixiviación de sulfuros de cobre

The correlactionship of bacterial population and oxidation-reduction potential in the bioleaching of sulfuric minerals by bacterial strain of Aciditiobacilus Ferrooxidans isolated from acid mine effluent was studied. The solubilization of copper and gold release from a mineral with sulphides exceeding 80% was evaluated. The experimental variables were: Pulp density at 1, 2 and 6% (W/V), concentration of ferrous sulfate as part of the 9k medium of 0, 3, 6, 9 and 15 gr/L.; maintaining constant temperature and pH. The tests were carried out in three consecutive stages, starting with inoculum containing 7.05x107 Cell/mL and then the one obtained in each previous stage, observing the variation in the periods of adaptation and growth. In the first stage the maximum bacterial density reached in 24 days was 4.75x107 Cell/mL with 6 g/L of ferrous sulfate. In the second stage a maximum density of 6.30x107 Cell/mL was obtained without the addition of ferrous sulfate. In the third stage the bacterial density reached 4.51x107 Cell/mL, with exponential growth starts at approximately 13, 8 and 3 days, respectively. Bacterial strains are successfully adapted in different media containing varying amounts of iron and sulfuric minerals, regardless of iron sulfate as part of the bacterial substrat.Se estudio la correlación de las variables población bacteriana y potencial de óxido reducción (ORP) en la biolixiviación de minerales sulfurados mediante cepa bacteriana de Acidithiobacilus Ferrooxidans aisladas a partir de efluente ácido de mina, buscando la solubilización del cobre y la liberación del oro presente en un mineral con sulfuros superior a 80%. Las variables de experimentación fueron: La densidad de pulpa a 1, 2 y 6 % (W/V), concentración de sulfato ferroso como parte del medio 9k de 0, 3, 6, 9 y 15 gr/L; manteniendo constante la temperatura, agitación del medio y el pH. Los ensayos se realizaron en tres etapas consecutivas, iniciándose con inoculo conteniendo 7.05x107 Cel/mL y luego, la obtenida en cada etapa previa, observándose la variación en los periodos de adaptación y crecimiento. En la primera etapa la máxima población bacteriana alcanzada fue de 4.75x107 Cel/mL en 24 días con 6 g/L de sulfato ferroso. En la segunda etapa se obtuvo una máxima densidad de 6.30x107 Cel/mL sin la adición de sulfato ferroso. En la tercera etapa la densidad bacteriana alcanzada fue de 4.51x107 Cel/mL., con inicios de crecimiento exponencial aproximadamente a los 13, 8 y 3 días, respectivamente. Las cepas bacterianas fueron adaptadas satisfactoriamente en distintos medios conteniendo cantidades variadas de hierro y minerales sulfurados, dando mejores resultados sin la adición de sulfato ferroso

Bifunctional P-Containing RuO2 Catalysts Prepared from Surplus Ru Co-Ordination Complexes and Applied to Zn/Air Batteries

An innovative synthetic route that involves the thermal treatment of selected Ru co−ordination complexes was used to prepare RuO2-based materials with catalytic activity for oxygen reduction (ORR) and oxygen evolution (OER) reactions. Extensive characterization confirmed the presence of Ru metal and RuP3O9 in the materials, with an improved electrocatalytic performance obtained from calcinated [(RuCl2(PPh3)3]. A mechanistic approach for the obtention of such singular blends and for the synergetic contribution of these three species to electrocatalysis is suggested. Catalysts added to carbon−based electrodes were also tested in all−solid and flooded alkaline Zn/air batteries. The former displayed a specific discharge capacity of 10.5 A h g−1 at 250 mA g−1 and a power density of 4.4 kW kg−1 cm−2. Besides, more than 800 discharge/charge cycles were reached in the flooded alkaline Zn/air batter

Electrochemical Behavior of Different Diffusional Redox Probes on a Porous Acetylene Black Electrode: Mass Transport Modes and Electrostatic Effects

The need for high-performance electrodes for electrical energy generation, conversion, and storage has increased the use of carbon nanomaterials as smart surface modifiers of working electrodes. Among carbon nanomaterials, common and inexpensive carbon blacks have spurred the scientific community’s interest due to their outstanding capabilities as electrode nanomodifiers, typically combined with an ionomer forming carbonaceous inks. Determining the key factors that can limit or enhance the overall electrochemical response of the employed redox-active species is essential to ascertain the impact on the performance of a hypothetical device, as well as to understand and elucidate reaction mechanisms. Moreover, maximizing the use of the area actually available for the electrochemical active species inside the carbon matrix is of paramount importance. Thus, in this work, the analysis of the electrochemical responses of six redox solution-soluble probes is investigated by cyclic voltammetry and a rotating disk electrode at a GC electrode modified with a metal-free carbon ink formed by a mixture of acetylene black and the ionomer Nafion. The experimental responses show mixed thin-layer and semi-infinite behavior to different degrees depending on the charge of the redox probe. The study of the causes underlying these findings reveals a strong electrostatic influence of the ionomer, leading to the appearance of blocking or trapping effects depending on the charge number of the redox probe. Such effects can compromise the validity of the well known and broadly used procedures of data analysis for porous electrodes, which is critically analyzed

A synchrotron x-ray diffraction and hard x-ray photoelectron spectroscopy study of Zn negative electrodes at different charge and discharge states of Zn/MnO2 batteries using an ionic liquid-based gel polymer electrolyte

Zn/MnO batteries including an ionic liquid-based gel polymer electrolyte (IL-GPE) have been discharged or discharged and then recharged reaching different states of charge. The Zn electrodes used in these Zn/MnO batteries are studied by HAXPES and synchrotron XRD techniques. Besides, HAXPES measurements are compared with the results obtained by a conventional XPS. Formation of Zn(OH) and ZnO is found in intermediate states of charge during charging and discharging. However, only ZnO is observed in the anode when a full discharging was carried out. Conversely, an entire charging process produces a complete reduction of all Zn species to metallic Zn. In addition, various techniques have confirmed the entrance of Triflate anions and NMP solvent molecules in the electrode, accompanying the Zn cations movement during the charging.The authors thank the financial support from the Spanish Ministerio de Economía y Competitividad (Ref. ENE2013-48816-C5-3-R and ENE2016-79282-C5-5-R) including FEDER funds and provision of synchrotron radiation facilities at ESRF BM25B line. A.U. thanks F. Séneca (Región de Murcia, Ref: 19882-GERM-15)