Desarrollo de semiconductores con estructuras tipo perovskitas para purificar el agua mediante oxidaciones avanzadas

En este trabajo se llevó a cabo la preparación a través del método sol-gel y la reacción en estado sólido de óxidos semiconductores pertenecientes a las familias del tipo perovskita simple, ABO3 y doble laminar, A2M2O7, como el NaTaO3, NaTaO3:A (A = La, Sm), y Sr2M2O7 (M = Ta, Nb), respectivamente. Éstos fueron probados en la reacción de degradación fotocatalítica de azul de metileno, cristal violeta y rojo alizarín S. En particular, la perovskita simple, NaTaO3:Sm, mostró la mejor eficiencia para la degradación de azul de metileno (t1/2 = 65 min), mientras que la perovskita doble laminar, Sr2Ta2O7, fue eficiente para degradar tanto el cristal violeta (t1/2 = 5 min), como el rojo alizarín S (t1/2 = 25 min). Para el caso del cristal violeta la eficiencia fue incluso mayor a la mostrada por la titania P25 Degussa. La eficiencia fotocatalítica mostrada por los óxidos tipo perovskita simple la hemos relacionado a la formación de su estructura cristalina y a los valores de área superficial específica, además del efecto favorable del dopante. Mientras que en el caso de los óxidos tipo perovskita laminar, la eficiencia se debió a la presencia de la fase cristalina y al pH del medio de reacción. Además, debido a que todos estos óxidos mostraron valores de Eg alrededor de 4.0 eV, su activida

Effect of milling time on mechanical properties of fly ash incorporated cement mortars

Abstract. Currently, thermal energy generation through coal combustion produces ash particles which cause serious environmental problems and which are known as Fly Ash (FA). FA main components are oxides of silicon, aluminum, iron, calcium and magnesium in addition, toxic metals such as arsenic and cobalt. The use of fly ash as a cement replacement material increases long term strength and durability of concrete. In this work, samples were prepared by replacing cement by ground fly ash in 10, 20 and 30% by weight. The characterization of raw materials and microstructure was obtained by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The final results showed that the grinding process significantly improves the mechanical properties of all samples when compared replacing a mortar made with cement by ground fly ash and the reference samples without added fly ash. The beneficial effect of the ground fly ash can increase the use of this product in precast concrete industr

Information and communication technologies as strategies to strengthen the Interpretation and production of texts

La interpretación y producción de textos siempre ha sido una temática de gran interés investigativo a nivel nacional, debido a los problemas vinculados con los bajos resultados obtenidos en las diferentes pruebas establecidas. Partiendo de esto el propósito de la investigación está dirigido a fortalecer en los estudiantes la competencia Interpretativa y productiva de textos a través de las Tecnologías de la información y comunicación. Se asume un abordaje metodológico desde la investigación cualitativa, orientada desde la investigación acción. La unidad de análisis estuvo constituida por 132 estudiantes de los grados 4 y 5, entre las edades de 0 a 19 años, que conforman las diferentes sedes de la IED Agropecuaria Nuestra Señora de las Mercedes. Los resultados arrojados dejaron ene videncia que al trabajar los temas referentes a la interpretación y producción de textos, se generó un incremento significado en los resultados académicos de los estudiantes; entregando productos de calidad en contenido e interpretación textual.The interpretation and production of texts has always been a topic of great research interest at the national level, due to the problems associated with the low results obtained in the different tests established. Based on this, the purpose of the research is aimed at strengthening students’ interpretive and productive competence in texts through information and communication technologies. It assumes a methodological approach from qualitative research, oriented from the action research. The analysis unit consisted of 132 students of grades 4 and 5, between the ages of 0 to 19 years, which make up the different venues of the IED Farming Our Lady of Mercy. The results thrown away showed that by working on issues related to the interpretation and production of texts, a significant increase in the students’ academic results was generated; delivering quality products in content and textual interpretation

Mechanical Properties and Durability of Composite Cement Pastes Containing Phase-Change Materials and Nanosilica

Escalating global surface temperatures are highlighting the urgent need for energy-saving solutions. Phase-change materials (PCMs) have emerged as a promising avenue for enhancing thermal comfort in the construction sector. This study assessed the impact of incorporating PCMs ranging from 1% to 10% by mass into composite Portland cement partially replaced by fly ash (FA) and nanosilica particles (NS). Mechanical and electrochemical techniques were utilized to evaluate composite cements. The results indicate that the presence of PCMs delayed cement hydration, acting as a filler without chemically interacting within the composite. The combination of FA and PCMs reduced compressive strength at early ages, while thermal conductivity decreased after 90 days due to the melting point and the latent heat of PCMs. Samples with FA and NS showed a significant reduction in the CO2 penetration, attributed to their pozzolanic and microfiller effects, as well as reduced water absorption due to the non-absorptive nature of PCMs. Nitrogen physisorption confirmed structural changes in the cement matrix. Additionally, electrical resistivity and thermal behavior assessments revealed that PCM-containing samples could reduce temperatures by an average of 4 °C. This suggested that PCMs could be a viable alternative for materials with thermal insulation capacity, thereby contributing to energy efficiency in the construction sector

Effect of Dopant Loading on the Structural and Catalytic Properties of Mn-Doped SrTiO3 Catalysts for Catalytic Soot Combustion

Soot particles have been associated with respiratory diseases and cancer. To decrease these emissions, perovskite-mixed oxides have been proposed due to their thermal stability and redox surface properties. In this work, SrTiO3 doped with different amounts of Mn were synthesized by the hydrothermal method and tested for soot combustion. Results show that at low Mn content, structural distortion, and higher Oads/Olat ratio were observed which was attributed to the high content of Mn3+ in Ti sites. On the other hand, increasing the Mn content led to surface segregation of manganese oxide. All synthesized catalysts showed mesopores in the range of 32–47 nm. In the catalytic combustion of soot, the samples synthesized in this work lowered the combustion temperature by more than 100 °C compared with the uncatalyzed reaction. The sample doped with 1 wt % of Mn showed the best catalytic activity. The activation energy of these samples was also calculated, and the order of decreasing activation energy is as follows: uncatalyzed > Mn0 > Mn8 > Mn4 > Mn1. The best catalytic activity for Mn1 was attributed to its physicochemical properties and the mobility of the oxygen from the bulk to the surface at temperatures higher than 500 °C

Determinação in vitro da produção de gás e conteúdo de energia metabolizável de alimentos para ruminantes incubados com excrementos de ovinos

An experiment was performed to determine the in vitro gas production at 3, 6, 9, 12, 24, 36 and 48 h of incubation with two types of inoculum collected from two Saint Croix sheep (T1: ruminal liquid, T2: excreta with yeast) in five diets for ruminants with different concentrate (C) and forage (F) ratios (100C:0F, 75C:25F, 50C:50F, 25C:75F y 0C:100F), with the aim to evaluate the feasibility of utilizing excreta instead of ruminal liquid as inoculum in the in vitro gas production (PGIV) technique, in order to determine the in vitro digestibility of organic matter (DIVMO) and metabolizable energy content (EM) in feedstuffs for ruminants. The PGIV registered with ruminal liquid was higher (P < 0.05), than with excreta + yeast as inoculum in each evaluated diet. However, utilizing simple linear regression, polynomial curves or correction factors developed in this research, similar results for PGIV, DIVMO and EM for ruminal liquid were estimated from gas production registered using excreta with yeast as an alternative inoculum.Se realizó un experimento para determinar la producción de gas in vitro a 3, 6, 9, 12, 24, 36 y 48 h de incubación, con dos inóculos colectados de dos ovinos Saint Croix (T1: líquido ruminal, T2: excretas con levadura), en cinco alimentos para rumiantes con diferentes proporciones de concentrado (C) y forraje (F), (100C:0F, 75C:25F, 50C:50F, 25C:75F y 0C:100F), con el fin de evaluar la factibilidad de utilizar excretas, en sustitución del líquido ruminal, como inóculo en la técnica de producción de gas in vitro (PGIV), para determinar la digestibilidad in vitro de la materia orgánica (DIVMO) y el contenido de energía metabolizable (EM) de alimentos para rumiantes. La PGIV registrada con líquido ruminal fue mayor (P < 0.05), a la obtenida utilizando excretas con levadura como inóculo en cada dieta evaluada. Sin embargo, utilizando modelos de regresión lineal simple, polinómica y factores de corrección, desarrollados en esta investigación, fue posible estimar resultados similares de PGIV, DIVMO y EM obtenidos con líquido ruminal, a partir de la producción de gas registrada con excretas con levadura como inóculo

Efeito do inóculo (líquido ruminal ou excreta) na produção de gases in vitro em rações para ovinos

An experiment was carried out with the objective of evaluating the effect of two types of inocula from Saint Croix sheep (T1: ruminal fluid, T2: excreta with yeast), in two types of feed with different proportions of concentrate (C) and forage (F), (75C:25F; 25C:75F), on gas production at 24, 36 and 48 h of incubation (in duplicate) in 100 mL syringes (n = 3 replicates per diet), in order to determine in a factorial arrangement 2 X 2, (with two inocula and two diets), if the excreta can replace ruminal fluid as inoculum in in vitro gas production. Gas production was higher with ruminal fluid than with excreta, and with the high-concentrate diet. In conclusion, the excreta inoculum with yeast can be used to estimate the gas production obtained with ruminal fluid in in vitro incubations of feed for sheep.Se realizó un experimento con el objetivo de evaluar el efecto de dos tipos de inóculos provenientes de ovinos Saint Croix (T1: líquido ruminal, T2: excretas con levadura), en dos tipos de alimentos con diferentes proporciones de concentrado (C) y forraje (F), (75C:25F; 25C:75F), sobre la producción de gas a 24, 36 y 48 h de incubación en duplicado en jeringas de 100 mL (n = 3 repeticiones), con el fin de determinar en un arreglo factorial 2 X 2, (con dos inóculos y dos dietas), si las excretas pueden sustituir al líquido ruminal como inóculo en la producción de gas in vitro. La producción de gas fue mayor con líquido ruminal que con excretas, y con la dieta alta en concentrado.  En conclusión, el inóculo de excretas con levadura puede ser utilizado para estimar la producción de gas obtenida con líquido ruminal en incubaciones de alimentos para ovinos.Foi realizado um experimento com o objetivo de avaliar o efeito de dois tipos de inóculos de ovelhas Saint Croix (T1: líquido ruminal, T2: excretas com levedura), em dois tipos de ração com diferentes proporções de concentrado (C) e volumoso ( F), (75C:25F; 25C:75F), na produção de gás às 24, 36 e 48 h de incubação (em duplicata) em seringas de 100 mL (n = 3 repetições por dieta), a fim de determinar em um arranjo fatorial 2 X 2, (com dois inóculos e duas dietas), se as excretas puderem substituir o fluido ruminal como inóculo na produção de gases in vitro. A produção de gás foi maior com o líquido ruminal do que com as excretas e com a dieta rica em concentrado. Em conclusão, o inóculo de excretas com levedura pode ser utilizado para estimar a produção de gases obtida com fluido ruminal em incubações in vitro de ração para ovinos

Nanopartículas semiconductoras: una alternativa para la degradación de contaminantes orgánicos presentes en agua residual y la generación de energía de manera sustentable

En el presente trabajo se llevó a cabo la síntesis y caracterización de nanopartículas de óxidos semiconductores, tipo perovskita de las familias con fórmula general, NaMO3:A (M = Ta y Nb; A = La, Sm, Nd e Y). Estos óxidos se obtuvieron a 600 y 800°C. Además, se encontró que estos semiconductores presentan excelentes propiedades como fotocatalizadores en las reacciones de degradación de contaminantes orgánicos, tales como rodamina B (RB) y azul de metileno (AM), así como en la reacción de conversión de agua en hidrógeno como fuente de energía. En particular, el fotocatalizador NaTaO3:Sm presentó el menor tiempo de vida media para ambas reacciones, degradación de RB (t1/2 = 92 min) y degradación de AM (t1/2 = 65 min). Este mismo material se probó en la reacción de conversión de agua utilizando el reactor prototipo diseñado y construido en nuestro laboratorio para la generación de hidrógeno. In the present work the synthesis and characterization of semiconductor nanoparticles perovskitetype of families with general formula NaMO3:A (M = Ta y Nb; A = La, Sm, Nd e Y) was carried out. These oxides were obtained at 600 and 800°C. Furthermore, it was found that these semiconductors showed excellent properties as photocatalysts in degradation reactions of organic pollutants, such as Rhodamine B (RB) and Methylene Blue (MB), as well as the water splitting reaction to produce H2 as energy source. Particularly, NaTaO3:Sm photocatalysts showed the lowest half time life for both organic degradation reactions, RB (t1/2 = 92 min) and MB (t1/2 = 65 min). This material was tested in a water splitting reaction using the prototype reactor designed and constructed in our laboratory for the generation of hydrogen

Effect of Carbon/Nitrogen Ratio, Temperature, and Inoculum Source on Hydrogen Production from Dark Codigestion of Fruit Peels and Sewage Sludge

This paper studies the use of fruit peel biomass and waste sludge from municipal wastewater treatment plants in the metropolitan area of Monterrey, Mexico as an alternative way of generating renewable energy. Using a Plackett–Burman experimental design, we investigated the effects of temperature, inoculum source, and the C/N (Carbon/Nitrogen) ratio on dark fermentation (DF). The results indicate that it is possible to produce hydrogen using fruit peels codigested with sewage sludge. By adjusting the C/N ratio in response to the physicochemical characterization of the substrates, it was revealed that the quantities of carbohydrates and nitrogen were sufficient for the occurrence of the fermentation process with biogas production greater than 2221 ± 5.8 mL L−1Reactor and hydrogen selectivity of 23% (366 ± 1 mL H2·L−1Reactor) at the central point. The kinetic parameters (Hmax= 86.6 mL·L−1, Rm = 2.6 mL L−1 h−1, and λ = 1.95 h) were calculated using the modified Gompertz model. The quantification of soluble metabolites, such as acetic acid (3600 mg L−1) and ethyl alcohol (3.4 ± 0.25% v/v), confirmed the presence of acetogenesis in the generation of hydrogen