Reseña histórica de la actividad minera y metalúrgica en Chile

El presente artículo mostrará una reseña histórica sobre la evolución de la metalurgia en Chile. Para eso comenzaremos con una exposición del trabajo de metales en la época prehispánica, siguiendo con el trabajo de metales durante la conquista europea, la extracción de salitre y posterior desarrollo de la metalurgia extractiva del cobre mediante la revisión de la historia de la Corporación Nacional del Cobre (CODELCO). Finalmente definiremos los desafíos que deberá enfrentar nuestra área en lo relativo al cuidado del medio ambiente que nos exigen los nuevos tiempos, entre otros. Palabras Clave: Historia del cobre; historia del salitre; Chile

Hardening by transformation and cold working in a hadfield steel cone crusher liner

This paper presents the characterization of a secondary cone crusher concave liner made of Hadfield steel used in Chilean mining after crushing copper minerals during all service life. During use, a cone crusher concave liner suffers indentation (cold working) and abrasion; this combination provides the concave with a layer that constantly renews itself, maintaining a surface highly resistant to abrasive wear. The results presented here were obtained using optical microscopy, microhardness test, measuring abrasion using the dry sand/rubber wheel apparatus, and x-ray diffraction peaks analysis through the classic Williamson–Hall method. After analysis of results, two hardened surfaces have been found—one a product of heat treatment and the other due to deformation during use. This work proposes ways to explain them; the first one uses a thermodynamic model to calculate stacking fault energy, and the second compares the liner with cold-rolled samples.Fil: Allende Seco, Rodrigo. Universidad de Santiago de Chile; ChileFil: Artigas, Alfredo. Universidad de Santiago de Chile; ChileFil: Bruna, Héctor. Universidad de Santiago de Chile; ChileFil: Carvajal, Linton. Universidad de Santiago de Chile; ChileFil: Monsalve, Alberto. Universidad de Santiago de Chile; ChileFil: Sklate Boja, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentin

Comportamiento bi-modal de una fundición gris y un acero estructural al carbono en corrosión atmosférica marina acelerada

De acuerdo a datos del último censo de la producción de la industria de las fundiciones [1], se observó que aproximadamente el 46% de la producción en la industria de las aleaciones ferrosas corresponde a la fundi-ción gris. Por ello que se hace interesante el investigar la resistencia que posee este material a la corrosión atmosférica, y así determinar el real tiempo de vida útil a la intemperie. Los del comportamiento de las fundi-ciones grises bajo corrosión atmosférica son escasos, debido estos toman largos periodos de tiempo para la caracterización en tiempo real.Con el propósito de validar un ensayo de corrosión atmosférica acelerada, se ha sometido a una fundición gris [2] y a un acero al carbono [3]. a 40 días de un ensayo acelerado [4], que involucra ciclos de humecta-ción en cámara de niebla salina, lavado y secado, determinando el espesor corroído en cada tiempo. Estos resultados, luego fueron comparados, con los obtenidos por Southwell et al. [5] luego de 16 años de exposi-ción a la intemperie en un ambiente marino (Canal de Panamá). El análisis de resultados reveló que ambos materiales presentan un comportamiento bi-modal, en concordancia con lo descrito por Melchers et al. [6, 7, 8], éste comportamiento se caracteriza por un punto de inflexión en la curva cinética de espesor corroído, lo que permite la validación de la metodología propuesta como medio para evaluar la resistencia a la corrosión atmosférica marina en poco tiempo

Removal of algae from biological cultures: a challenge for electrocoagulation?

BACKGROUND In the search for novel technologies for the treatment of urban wastewater, combined anaerobic–algae membrane bioreactors have become a very interesting choice. Recovery of algae produced in these reactors has become the key point to obtain a good economic efficiency with this technology. In this work, electrocoagulation is studied as an alternative for the coarse removal of algae from a biological culture. RESULTS Results demonstrate that the electrochemical technology is a suitable technology for this purpose allowing the removal of more than 90% of the algae without modifying significantly the pH and with an operating cost below 0.04 € m−3. The same general trends are observed for applied current charge and current density supplied when aluminum or iron are used as electrodes although aluminum was much more efficient. CONCLUSIONS The dose of coagulant reagents required is very low, indicating that coagulant generated in the process is very efficiently used. The best results in terms of algae and turbidity removals are obtained operating at low current densities with aluminum electrodes. According to pH and z-potential values, insoluble metal hydroxide and anion M(OH)4− seems to be the primary coagulation species involved in the electrocoagulation process.ANTECEDENTES En la búsqueda de nuevas tecnologías para el tratamiento de aguas residuales urbanas, los biorreactores combinados anaerobios-membrana de algas se han convertido en una opción muy interesante. La recuperación de las algas producidas en estos reactores se ha convertido en el punto clave para obtener una buena eficiencia económica con esta tecnología. En este trabajo se estudia la electrocoagulación como alternativa para la remoción gruesa de algas de un cultivo biológico. RESULTADOS Los resultados demuestran que la tecnología electroquímica es una tecnología adecuada para este fin permitiendo eliminar más del 90% de las algas sin modificar significativamente el pH y con un coste operativo inferior a 0,04 € m −3 . Se observan las mismas tendencias generales para la carga de corriente aplicada y la densidad de corriente suministrada cuando se usan aluminio o hierro como electrodos, aunque el aluminio fue mucho más eficiente. CONCLUSIONES La dosis de reactivos coagulantes requerida es muy baja, lo que indica que el coagulante generado en el proceso se utiliza de manera muy eficiente. Los mejores resultados en términos de remoción de algas y turbidez se obtienen operando a bajas densidades de corriente con electrodos de aluminio. De acuerdo con los valores de pH y potencial z, el hidróxido de metal insoluble y el anión M(OH) 4− parecen ser las principales especies de coagulación involucradas en el proceso de electrocoagulación

Effect of sludge age on the consortium of microorganisms microbial consortia developed in MFCs

BACKGROUND: This work is focused on the assessment of the performance of mini-scale air-breathing microbial fuel cells (MFCs),by monitoring the evolution of the bio-electrogenic activity for a period of 40 days and by comparing the microorganismspopulations developed in each of the MFCs after this period.RESULTS: Five MFCs were operated at sludge ages ranging from 1.4 to 10.0 days. Results showed the superb performance of theMFC operating under a sludge age of 2.5 days. Desulfuromonas, Syntrophothermus, Solitalea, Acholeplasma, Propionicimonas,Desulfobacula and Sphaerochaeta are proposed as potentially responsible for the bio-electrogenic activity.CONCLUSIONS: Microbial population analysis through Illumina amplicon sequencing demonstrated that despite all MFCsbeing seeded with the same mixed culture inoculum, the biological cultures developed in the suspension and the biofilm arecompletely different and depend strongly on sludge age.© 2017 Society of Chemical Industry

Isoprene photochemistry over the Amazon rainforest

Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO_2) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4–0.6. This result implies a ratio of the reaction rate of ISOPOO with HO_2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest

Isoprene photochemistry over the Amazon rainforest

Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO2) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK+MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK+MACR spanned 0.4-0.6. This result implies a ratio of the reaction rate of ISOPOO with HO2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (&gt;1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (&lt;60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest

Airborne observations reveal elevational gradient in tropical forest isoprene emissions

Isoprene dominates global non-methane volatile organic compound emissions, and impacts tropospheric chemistry by influencing oxidants and aerosols. Isoprene emission rates vary over several orders of magnitude for different plants, and characterizing this immense biological chemodiversity is a challenge for estimating isoprene emission from tropical forests. Here we present the isoprene emission estimates from aircraft eddy covariance measurements over the Amazonian forest. We report isoprene emission rates that are three times higher than satellite top-down estimates and 35% higher than model predictions. The results reveal strong correlations between observed isoprene emission rates and terrain elevations, which are confirmed by similar correlations between satellite-derived isoprene emissions and terrain elevations. We propose that the elevational gradient in the Amazonian forest isoprene emission capacity is determined by plant species distributions and can substantially explain isoprene emission variability in tropical forests, and use a model to demonstrate the resulting impacts on regional air quality

Molecular composition of organic aerosols in central Amazonia: An ultra-high-resolution mass spectrometry study

The Amazon Basin plays key role in atmospheric chemistry, biodiversity and climate change. In this study we applied nanoelectrospray (nanoESI) ultra-high-resolution mass spectrometry (UHRMS) for the analysis of the organic fraction of PM2.5 aerosol samples collected during dry and wet seasons at a site in central Amazonia receiving background air masses, biomass burning and urban pollution. Comprehensive mass spectral data evaluation methods (e.g. Kendrick mass defect, Van Krevelen diagrams, carbon oxidation state and aromaticity equivalent) were used to identify compound classes and mass distributions of the detected species. Nitrogen-and/or sulfur-containing organic species contributed up to 60% of the total identified number of formulae. A large number of molecular formulae in organic aerosol (OA) were attributed to later-generation nitrogen-and sulfur-containing oxidation products, suggesting that OA composition is affected by biomass burning and other, potentially anthropogenic, sources. Isoprene-derived organosulfate (IEPOX-OS) was found to be the most dominant ion in most of the analysed samples and strongly followed the concentration trends of the gas-phase anthropogenic tracers confirming its mixed anthropogenic-biogenic origin. The presence of oxidised aromatic and nitro-aromatic compounds in the samples suggested a strong influence from biomass burning especially during the dry period. Aerosol samples from the dry period and under enhanced biomass burning conditions contained a large number of molecules with high carbon oxidation state and an increased number of aromatic compounds compared to that from the wet period. The results of this work demonstrate that the studied site is influenced not only by biogenic emissions from the forest but also by biomass burning and potentially other anthropogenic emissions from the neighbouring urban environments. © 2016 Author(s)