Abstract Organic matter-in-aqueous entrainment is a serious problem in the hydrometallurgical extraction of copper from ore. Current inefficiencies, changes in the morphology and orientation of cathode deposit are some of the problems when organic matter is present in the advance electrolyte. In addition, negative effects upon metabolic activity of bioleaching microorganisms are reported due to entrained organic matter in the raffinate electrolyte. In view of these problems, the objective of this study was to evaluate ozonation as an alternative method for the removal of entrained organic matter present in an advanced electrolyte. For this purpose, ozonation during 30 min of synthetic solutions using a bubble glass column reactor at different ozone concentrations, flow rates and temperatures were studied. It was found that the increase in all of these operating parameters is not necessarily associated with an increase of the removal efficiency, and their effects on the mass transfer rate, chemical reaction rate, ozone solubility and contact time play a decisive role in the ozonation process. Thus, the best operating conditions were found at 6.7 wt.%, 1 L min-1 and 27 °C and reached a removal efficiency of 94.5%. This result demonstrated that removal of entrained organic matter in strongly acid solution by ozonation could be an alternative technology.

Abstract: The famous El Castillo pyramid, located in Chichen Itza, towards the northern portion of the Yucatan Peninsula, Mexico, is an emblematic structure of this archaeological site and recognized as one of the man-made world seven wonders. The archaeologists that restored this structure during the 1930’s discovered a smaller pyramid inside this preHispanic edifice, which corresponded to an older Mayan period. The possibility of finding other construction periods inside this edifice should be important in order to reconstruct the Mayan history of the region. Previous geophysical studies carried out in 2014 by the authors, showed a buried natural cavity partially filled with water beneath El Castillo pyramid, using novel Electrical Resistivity Tomography (ERT) arrays. Employing a similar technique, a series of flat electrodes were deployed on each of the 9 bodies (or levels) conforming the pyramid plus the base of the structure, keeping a constant distance between each electrode. A precise topographic control for each electrode was fulfilled and introduced in the inversion process. 37,520 observations inside the pyramid were computed. So far, five of the 10 observation levels (19,400 points), were processed. Horizontal and vertical slices of this inverted image were analyzed. Examining the differences in the resistivity values and their gradients, allowed to locate the first substructure (explored in the 1930’s), as well as to infer a second substructure inside the previous one. An ERT-2D profile was surveyed inside El Castillo pyramid at the interior of a tunnel excavated in 1934 and the stairway of the first inner pyramid. Results from this study seem to confirm the evidence of a second substructure within El Castillo’s interior. Such feature possesses a probable intact chamber (a rectangular room 3 m high) on its upper part and inferred dimensions of 10 m high and 23 m per side at its base, assuming that the end of this profile lies on the middle of substructure 2. When the inversion will be carried out for the 10 levels, a better resolution will be reached for the upper portions of the resistivity model.

Resumen: La famosa Pirámide del Castillo, ubicada en Chichén Itzá, hacia la parte norte de la Península de Yucatán, México, es una estructura emblemática de este sitio arqueológico y elegida como una de las siete maravillas hechas por el hombre. Los arqueólogos que restauraron esta estructura durante los años 30 descubrieron una pirámide más pequeña dentro de este edificio prehispánico, que correspondía a un período maya más antiguo. La posibilidad de encontrar otros períodos de construcción dentro de este edificio es muy importante para reconstruir la historia maya de la región. Estudios geofísicos anteriores llevados a cabo por los autores en 2014, utilizando nuevos arreglos de Tomografía de Resistividad Eléctrica (TRE), mostraron una cavidad natural parcialmente llena de agua dulce debajo de la Pirámide de El Castillo. Empleando una técnica similar, se desplegó una serie de electrodos planos en cada uno de los 9 cuerpos (o niveles) que conformaban la pirámide más la base de la estructura, manteniendo constante la distancia entre cada electrodo. Se realizó un control topográfico preciso para cada electrodo, el que se introdujo en el proceso de inversión. Se calcularon 37.520 observaciones dentro de la pirámide. Cinco de los 10 niveles de observación (19.400 puntos), han sido procesados hasta ahora. Se analizaron secciones horizontales y verticales de esta imagen invertida. Examinando las diferencias en los valores de resistividad y sus correspondientes gradientes se pudieron localizar, la primera subestructura (explorada en la década de 1930), así como inferir una segunda subestructura dentro de la anterior. Se levantó un perfil ERT-2D dentro de la pirámide de El Castillo, al interior de un túnel excavado en 1934 y la escalera de la primera pirámide interna. Los resultados de este estudio parecen confirmar la evidencia de una segunda subestructura dentro del interior de El Castillo. Dicho rasgo resistivo posee una cámara probablemente intacta (una habitación rectangular de 3 m de altura) en su parte superior y dimensiones inferidas de 10 m de altura y 23 m por lado en su base, suponiendo que el final de este perfil se encuentre en el centro de la subestructura 2. Cuando la inversión se lleve a cabo integrando los 10 niveles, se tendrá una mejor resolución para las porciones superiores del modelo de resistividad.

This paper presents an alternative process for the conventional zinc electrowinning, which consists of a cell of two compartments separated by a anion exchange membrane. One of them contains a zinc sulphate catholyte and sulfuric acid while the anolyte solution contains ferrous sulfate and sulfuric acid. By using a membrane the classical lead anode may be replaced, as well as the main oxidation reaction of water, for that of the ferrous ion to ferric ion. This leads to significant savings in specific energy consumption of the overall process and eliminates the classic problem of acid mist in electrowinning cells. The results show that the proposed process consumes 30% less cell potential compared to conventional electrowinning cell.

Considerando que el biodiesel se está convirtiendo en una solución viable para algunos problemas energéticos y medioambientales, la investigación de materias primas para su producción es un tema de creciente interés. Este estudio presenta los resultados de una investigación dedicada al análisis preliminar de varias especies vegetales (biomasa), potencialmente útiles para producir biodiesel. La zona de bioprospección es una región de la costa pacifica colombiana. Las especies promisorias recolectadas fueron sometidas a diferentes pruebas normalizadas ASTM para definir propiedades que faciliten su evaluación. Algunas de las especies fueron sometidas a un proceso de transesterificación. Adicionalmente, se realiza una comparación entre las propiedades termo-físicas de los biodiesel y las propiedades del diesel comercial. Las pruebas de rendimiento de estos biocombustibles en los motores de encendido por compresión, particularmente la eficiencia, el consumo y la potencia a diferentes RPM del motor, se presentan en este trabajo.

Given that biodiesel is emerging as a viable solution for some energy and environmental problems, research on raw materials appropriate for its production is a matter of growing interest. In this study we present the results of research devoted to preliminary analysis on several vegetable (biomass) species potentially useful for producing biodiesel. The bioprospection zone is a region on the Colombian Pacific coast. The candidate species collected underwent different standardized ASTM tests in order for us to define properties that facilitate their evaluation. Some of the species underwent a transesterification process. Comparisons between the thermo-physical properties of the biofuels obtained and the properties of commercial diesel were carried out. Also, performance tests for these biofuels were conducted in compression ignition engines, particularly evaluating efficiency, fuel consumption, and potency at different RPMs.

La humedad relativa y la temperatura en el interior de las cavas maduración del proceso de fabricación de quesos, son de interés a controlar porque determinan las características finales del producto. Las investigaciones se enfocan al control de estas dos variables en los rangos de diseño y operación recomendados, que permitan plantear sistemas de reducción de humedad más eficientes, que utilicen controles automáticos, semiautomáticos, manuales y artesanales. La metodología para establecer el rango de control fue: Se realizó un diseño completamente aleatorizado de efectos fijos. Se tomó como unidad experimental (Ue), la cava de maduración de queso, se establecieron 4 tratamientos con 17 repeticiones para operar la cava: mecheros y extractores encendidos; mecheros encendidos; extractores encendidos; mecheros y extractores apagados. Las variables de respuesta de interés en este estudio fueron la humedad relativa y la temperatura. Se tomó como referente de comparación los rangos de diseños recomendados en cavas de maduración: HR: 85 a 90% y T: 12 a 16 °C. El estudio se realizó en 12 días. En la sistematización de los datos se utilizó el paquete estadístico Social Packet Stadistic Sciences (SPSS) versión libre 11.5. Los rangos de control encontrados para operar la cava de maduración de quesos fueron 93 a 100 % para humedad relativa (HR) y 11 a 16°C para la temperatura (T), los cuales corresponde al tratamiento cuatro del diseño experimental. El límite superior de 100 % HR y 16°C de T, se definió como la condición más critica del proceso a ser controlada, en comparación con las recomendadas por diseño (HR= 85 %, T= 12°C)y las reportadas por otros investigadores (HR= 80 a 90 % HR, T= 12 °C). Mientras los valores que están fuera del rango definieron el proceso no controlado.

The relative humidity and temperature inside in the Chambers of Maturation cheese making process are of interest to control that determine the final characteristics of the product. The investigations focus on the control of these two variables in the ranges recommended design and operation, enabling raise moisture reduction systems more efficient, using automatic controls, semi-automatic, manual and craft. The methodology to establish the control range was: A completely randomized design of fixed effects. Was taken as the experimental unit (Ue), the chamber of maturation were 4 treatments with 17 repetitions to operate the Chamber: lighters and extractor lit, lit lighters, extractor lit, cigarette lighters and extractor off. The response variables of interest in this study were the relative humidity and temperature. Was taken as reference for comparison of designs ranges recommended the Chamber of Maturation: HR: 85-90% and T: 12-16°C. The study was conducted in 12 days. The systematization of the data, using the statistical package Packet Stadistic Social Sciences (SPSS) free versión 11.5. Control ranges were found to operate the Chamber of Maturation of cheese were 93-100% for relative humidity (HR) and 11-16°C for temperature (T), which corresponds to the four treatment experimental design. The upper limit of 100% HR and T: 16°C, was identified as the most critical condition of the process to be controlled, compared with those recommended by design (HR = 85%, T= 12°C) and those reponed by other researchers (HR = 80-90%, T= 12°C). While the values are outside the range defined like not controlled process.

A umidade relativa e temperatura no interior das cavas maduragáo do processo de fabricação de queijos são de interesse a controlar por que determinam as características fináis do produto. As investigações se enfocam ao controle destas variáveis ñas classes de desenho e operação recomendados, que permitam expor sistemas de redução de umidade mais eficientes, que empreguem controles automáticos, semi-automáticos, manuais e artesanais. A metodología para estabelecera categoría do controle foi: realizouse um desenho completo aleatorizado de efeitos fixos. Tomouse como unidade experimental (Ue), a cava de maduração de queijo. Se estabeleceram 4 tratamentos com 17 repetições para operar a cava: bico de gas e extratores aceso; bicos de gas acesos; extratores acesos; bico de gas e extratores apagados. As variáveis de resposta de interesse neste estudo foram a umidade relativa e a temperatura. Tomou-se como referente de comparação as categorías de desenho recomendados em cavas de maduração: HR: 85 a 90% eT:12a16°C. O estudo se realizou em 12 dias. Na sistematização dos dados se empregou o pacote estatístico Social Packet Stadistic Sciences (SPSS) versão livre 11.5. As categorías de controle encontradas para operar a cava de maduração de queijos foram 93 a 100% para umidade relativa (HR) e 11ª 16° C para temperatura (T), os quais correspondem ao tratamento quatro do desenho experimental. O limite superior de 100% HRe16°C definiu-se como a condição mais crítica do processo a ser controlada, em comparação com as recomendadas pelo desenho (HR=85%, T= 12° C) e as reportadas pelos outros investigadores (HR=80 a 90% HR, T= 12° C). No entanto os valores que estáo fora das categorías definiram o processo não controlado.

This paper shows an alternative to the classic electro winning copper process using a cell based on reactive electrodialysis, which consists of two compartments separated by an anionic membrane, one of which contains the copper sulphate catholyte, where the cathode is located, and the other compartment contains the ferrous sulfate anolyte, where the anode is located. In this type of cell the anodic reaction is the oxidation of iron (Fe2+ to Fe3+), which consumes less energy than the classic water oxidation. Moreover, this new anodic reaction does not produce acid mist.

El presente trabajo evalúa el comportamiento de la temperatura del flujo de aire en un colector solar de lecho de rocas, mediante un modelo matemático que simula las temperaturas del flujo de aire a la entrada y salida del colector. El modelo relaciona la geometría, la radiación incidente en el colector y las constantes propias del colector determinadas experimentalmente. Para el análisis se realizaron tres pruebas en las que se midieron las temperaturas del ambiente, de entrada y salida en el colector y la radiación solar incidente.

The present work evaluates the behavior of the temperature of the flow of air in a solar collector of channel of rocks, by means of a mathematical model that simulates the temperatures from the flow of air to the entrance and exit of the collector. The pattern relates the geometry, the incident radiation in the collector and the constants own collector determined experimentally. For the analysis they were carried out three tests in those that the temperatures of the atmosphere were measured, of entrance and exit in the collector and the solar incident radiation.

Anodic dissolution of synthetic chalcocite (previously obtained by copper precipitation with S and S0(2) in ammonia media) in two different electrolytic cells is described. One cell has a circular graphite anode placed horizontally, surrounded by a stainless steel cylinder as cathode, and the other has a rectangular basket-shaped graphite anode, with a rectangular stainless steel cathode placed in front of it. The electrolysis was performed at 0.2 A and 50 °C, the electrolyte contained 20 to 40 g L-1 of Cuand 100 to 160 g L-1 of H2S0(4), and the initial reactions took place at low potential (0.4-0.6 V) until the transformation of Cu2S intoCuS, detected by the considerable increase in cell potential. Anodic and cathodic efficiencies greater than 100% and 95%, respectively, were obtained. The hight anodic efficiencie is duetofaradic and chemical dissolution too. It is also shown that the (CuS) produced as waste material can replace elemental sulphur as copper precipitating agent in ammoniacal media.

El presente trabajo expone los fundamentos más comunes en que se basan los sistemas de refrigeración solar para las aplicaciones agroindustriales.

The present work exposes the most common principles that the systems of solar refrigeration are based for agroindustrials applications.