Life Cycle Assessment of Raw and Fe-Modified Biochars: Contributing to Circular Economy.

Biochar is a carbonaceous material, which can be decorated with metals, that has been garnering attention to be used in the treatment of water due to its contribution to waste management and circular economy. This study presents the life cycle assessment (LCA) regarding the generation of Pinus patula raw biochar and its modification with iron (Fe-modified biochar). SimaPro 9.3.0.3 software was used to simulate the environmental impacts of both carbonaceous materials. The potential environmental effects obtained from the production of Pinus patula raw biochar were mainly ascribed to the source of energy utilized during this process. The potential impacts demonstrated that the generation of gases and polycyclic aromatic hydrocarbons are the main concern. In the case of Fe-modified biochar, the potential environmental effects differed only in the stage of the biomass modification with the metal. These effects are associated with the extraction of Fe and the generation of wastewater. These findings provide an insight into the environmental effects linked to the production of raw and Fe-modified biochar. However, further LCA research should be performed concerning other materials and compounds than can be generated during the biomass thermochemical conversion.

Impact of Indenter Size and Microrelief Anisotropy on the Tribological Behavior of Human Skin.

Everyday, we interact with screens, sensors, and many other devices through contact with the skin. Experimental efforts have increased our knowledge of skin tribology but are challenged by the fact that skin has a complex structure, undergoes finite deformations, has nonlinear material response, and has properties that vary with anatomical location, age, sex, and environmental conditions. Computational models are powerful tools to dissect the individual contribution of these variables to the overall frictional response. Here, we present a three-dimensional high-fidelity multilayer skin computational model including a detailed surface topography or skin microrelief. Four variables are explored: local coefficient of friction (COF), indenter size, mechanical properties of the stratum corneum, and displacement direction. The results indicate that the global COF depends nonlinearly on the local COF, implying a role for skin deformation on the friction response. The global COF is also influenced by the ratio of the indenter size to the microrelief features, with larger indenters smoothing out the role of skin topography. Changes in stiffness of the uppermost layer of skin associated with humidity have a substantial effect on both the contact area and the reaction forces, but the overall changes in the COF are small. Finally, for the microrelief tested, the response can be considered isotropic. We anticipate that this model and results will enable the design of materials and devices for a desired interaction against skin.

Parametric Analysis of a Gasification-Based Cookstove as a Function of Biomass Density, Gasification Behavior, Airflow Ratio, and Design.

The energy performance and emissions (carbon monoxide and total suspended particulate matter) of a biomass gasification-based cookstove under a modified water boiling test (WBT 4.2.3 protocol) were characterized here. The controllable process parameters analyzed were the biomass bulk density (pellets-WP and chips-WCH) and the combustion-air/gasification-air ratio (2.8, 3.0, and 3.2). Moreover, a design parameter of the cookstove was analyzed through two combustion chamber designs (combustion chambers 1 and 2). The cookstove was characterized in detail considering the complete cookstove (control volume 1), the combustion chamber (control volume 2), and the gasification process (control volume 3). The cookstove reached an average efficiency of 25.2% for pellets and 24.1% for chips. The best behavior for the cookstove was achieved when pellets were used, which is attributed to their higher bulk density and to the fact that during their gasification process, the biochar yield was 12% higher, while the biomass consumption decreased by 16% compared to the chips. The carbon monoxide specific emissions were 2.78 g/MJd for pellets and 2.75 g/MJd for chips. On average, the cookstove released total suspended particulate matter between 74.11 and 122.70 mg/MJd. The cookstove low emissions are ascribed to the proper combustion air flow and the combustion chamber design, which favored the mixing between producer gas and combustion air.

Changes in the three-dimensional microscale topography of human skin with aging impact its mechanical and tribological behavior.

Human skin enables interaction with diverse materials every day and at all times. The ability to grasp objects, feel textures, and perceive the environment depends on the mechanical behavior, complex structure, and microscale topography of human skin. At the same time, abrasive interactions, such as sometimes occur with prostheses or textiles, can damage the skin and impair its function. Previous theoretical and computational efforts have shown that skin's surface topography or microrelief is crucial for its tribological behavior. However, current understanding is limited to adult surface profiles and simplified two-dimensional simulations. Yet, the skin has a rich set of features in three dimensions, and the geometry of skin is known to change with aging. Here we create a numerical model of a dynamic indentation test to elucidate the effect of changes in microscale topography with aging on the skin's response under indentation and sliding contact with a spherical indenter. We create three different microrelief geometries representative of different ages based on experimental reports from the literature. We perform the indentation and sliding steps, and calculate the normal and tangential forces on the indenter as it moves in three distinct directions based on the characteristic skin lines. The model also evaluates the effect of varying the material parameters. Our results show that the microscale topography of the skin in three dimensions, together with the mechanical behavior of the skin layers, lead to distinctive trends on the stress and strain distribution. The major finding is the increasing role of anisotropy which emerges from the geometric changes seen with aging.

Photolysis of a mixture of anthracene and benzo[a]pyrene at ultra-trace levels in natural water with disinfection purposes.

The photodegradation of anthracene (AN) and benzo[a]pyrene (BaP), two priority polycyclic aromatic hydrocarbons (PAHs), was examined at ultra-trace levels in surface water to elucidate their behaviour under several irradiance values and types of radiation. The emitting flux and the spectrum of the lamps were found to develop a crucial role in AN and BaP degradation since removal efficiencies of the target contaminants higher than 99% were found after 15 min of irradiation under an ultraviolet C (UVC) irradiance of 0.63 mW/cm2, corresponding to a fluence of 560.25 mJ/cm2. On the other hand, although ultraviolet A (UVA) lamps exhibited a higher irradiance compared to that of UVC lamps, they were not efficient for degrading the target PAHs. The removal kinetic studies corroborated these findings, being the AN elimination rate in surface water higher than that in deionized water at optimal operating conditions. Disinfection potential was also measured. A rapid microbial load inactivation, in terms of total coliforms naturally contained in the water matrix studied, was evidenced within 15 min of treatment for the fluence referred. However, after 24 hr in the dark, a regrowth was observed. Additionally, photolysis products more toxic than the parent compounds were found, which were not removed even by extending the treatment time. In this regard, it can be concluded that the individual action of UVC light for removing AN and BaP with disinfection purposes is not an efficient treatment; therefore, the use of radiation in combination with other kinds of treatments is required.

Evaluation of the UV/H2O2 system for treating natural water with a mixture of anthracene and benzo[a]pyrene at ultra-trace levels.

The presence of polycyclic aromatic hydrocarbons, such as anthracene (AN) and benzo[a]pyrene (BaP), in water has become a problem of great concern due to the detrimental health effects caused to humans and living beings. In this work, the efficiency of the UV/H2O2 system for degrading the target compounds at ultra-trace levels in surface water has been evaluated. For this purpose, a previous optimization step using a face-centered central composite experimental design has been conducted, considering the effect of the UV-C irradiance and the initial concentration of H2O2. It was evidenced that under optimal operating conditions (11 mg L-1 H2O2 and 0.63 mW cm-2 irradiance), AN and BaP removal percentages were higher than 99.8%. Additionally, 69.3% of the organic matter, in terms of total organic carbon, was mineralized without the production of transformation by-products more harmful than the parent compounds. These findings demonstrate the oxidation capacity of the examined system in a natural matrix for degrading micropollutants that cannot be converted through conventional treatment processes. Consequently, new horizons are opened for the effective use of the UV/H2O2 system for drinking water production, providing the accomplishment of other regulated parameters related to water quality.

Total coliform inactivation in natural water by UV/H2O2, UV/US, and UV/US/H2O2 systems.

The presence of pathogens in drinking water can seriously affect human health. Therefore, water disinfection is needed, but conventional processes, such as chlorination, result in the production of dangerous disinfection by-products. In this regard, an alternative solution to tackle the problem of bacterial pollution may be the application of advanced oxidation processes. In this work, the inactivation of total coliforms, naturally present in a Colombian surface water by means of UV/H2O2, UV/US, and the UV/US/H2O2 advanced oxidation processes, was investigated. Under the investigated conditions, complete bacterial inactivation (detection limit equal to 1 CFU 100 mL-1) was found within 5 min of treatment by UV/H2O2 and UV/US/H2O2 systems. UV/US oxidation process also resulted in total bacterial load elimination, but after 15 min of treatment. Bacterial reactivation after 24 h and 48 h in the dark was measured and no subsequent regrowth was observed. This phenomenon could be attributed to the high oxidation capacity of the evaluated oxidation systems. However, the process resulting in the highest oxidation potential at the lowest operating cost, in terms of energy consumption, was UV/H2O2 system. Therefore, UV/H2O2 advanced oxidation system can be used for disinfection purposes, enabling drinking water production meeting the requirements of regulated parameters in terms of water quality, without incurring extremely high energy costs. Nonetheless, further researches are required for minimizing the associated electric costs.

Direct large-volume injection analysis of polycyclic aromatic hydrocarbons in water / Análisis de inyección directa en gran volumen de hidrocarburos aromáticos policíclicos en agua / Análise de injeção direta de grande volume de hidrocarbonos aromáticos policíclicos em água

Abstract Due to the health risks for both humans and living beings caused by polycyclic aromatic hydrocarbons (PAHs), the monitoring of these compounds in environmental matrices is mandatory. This work proposes an analytical method for analyzing anthracene (AN) and benzo[a]pyrene (BaP), two of the most representative PAHs, at ultra-trace concentrations in water, employing direct injection of large volumes of samples coupled with reversed-phase high-performance liquid chromatography. For this purpose, principal component analysis was used to examine the behavior of AN and BaP within the chromatographic system. Results showed that AN and BaP chromatographic behavior can be described by three models representing their identification, the quantification of AN and that of BaP, respectively. The factors affecting the obtained models, such as the injection volume, column temperature, flow rate, strength of the mobile phase, and the excitation and emission wavelengths, were examined and optimized by means of design of experiments. Finally, the analytical method was validated, obtaining promising limits of detection and quantification. The developed analytical method was demonstrated to be useful for a sensitive analysis of the target analytes in relatively clean natural water matrices.

Resumen Los hidrocarburos aromáticos policíclicos (HAPs) causan problemas en la salud de los seres humanos y seres vivos, por lo que se requiere un monitoreo de estos compuestos en matrices ambientales. Este trabajo propone un método analítico para analizar el antraceno (AN) y el benzopireno (BAP), los hidrocarburos más representativos en concentraciones de ultra trazas en el agua, empleando inyección directa en grandes volúmenes en muestras acopladas a la fase inversa con cromatografía líquida de alto rendimiento. Por tal razón, se utilizó el análisis de componentes principales para examinar el comportamiento de AN y BAP en el sistema cromatográfico. Los resultados mostraron que el comportamiento cromatográfico de AN y BAP podría describirse por medio de tres modelos que representan su identificación, la cuantificación de AN y de BAP, respectivamente. Se examinaron los factores que afectan a los modelos obtenidos, como el volumen de inyección, la temperatura de la columna, la tasa de flujo, la fuerza de la fase móvil, y las longitudes de las ondas de excitación y emisión, y se optimizaron mediante el diseño de experimentos. Finalmente, se validó el método analítico, obteniendo límites de detección y cuantificación. Se demostró que el método analítico desarrollado fue útil para el análisis sensible de los analitos en matrices de agua natural relativamente limpia.

Resumo Devido aos riscos para a saúde tanto para humanos como para os seres vivos em geral causados pelos hidrocarbonos aromáticos policíclicos (HAPs), o monitoramento de estes compostos em matrizes ambientais é prioritário. Este trabalho propõem um método analítico para analisar antraceno (AN) e benzo[a]pireno (BaP), dois dos hidrocarbonos mais representativos, em concentrações de ultra traços em água, empregando injeções diretas de grandes volumes de amostra acoplada a cromatografia líquida de alta eficiência em fase reversa. Usando Análises por Componentes Principais e desenho experimental, foram avaliados os efeitos de diversos fatores que afetam o sistema cromatográfico, tais como o volume de injeção, a temperatura da coluna, fluxo, forca da fase móvel e comprimentos de onda de excitação e emissão. Os resultados demonstraram que o comportamento cromatográfico de AN e BaP pode ser descrito por meio de três que representam sua identificação, quantificação de AN e de BaP, respectivamente. Os resultados mostraram que o comportamento cromatográfico de NA e BAP poderia ser descrito por meio de três modelos que representam sua identificação, a quantificação de NA e de BAP, respectivamente. Examinaram-se os fatores que afetam aos modelos obtidos, como o volume de injeção, a temperatura da coluna, a taxa de fluxo, a forca da fase móvel, e as longitudes das ondas de excitação e emissão, e se otimizaram mediante o desenho experimental. Finalmente, se validou o m todo analítico, obtendo os limites de detecção e quantificação. O método analítico desenvolvido demonstrou ser útil para uma análise sensível para os compostos de interesse em matrizes de água natural relativamente limpas.

Prótesis parcial fija: análisis biomecánico sobre distribución de esfuerzos entre tresalternativas de retención / Fixed partial prosthesis: biomechanical analysis of stress distribution among three

Introducción: el propósito de este estudio fue analizar la distribución de los esfuerzos entre tres alternativas deretención de una prótesis dental parcial fija de tres unidades, utilizando el método de elementos finitos (MEF). Métodos: se realizaron tres modelos tridimensionales en elementos finitos del tramo dental anterior superior, restaurando uno con postes colados, otro con postes prefabricados y el tercero con implantes. Los modelos del tramo restaurado fueron modelados con hueso esponjoso, hueso cortical, ligamento periodontal, encía, raíz, gutapercha, cemento resinoso, poste, muñón de resina (modelos postes prefabricados), cofia metálica y corona cerámica. El material de los postes considerado para el análisis fue una aleación de metal noble (postes colados) y fibra de vidrio (postes prefabricados). Los postes fueron cementados con cemento resinoso. Se hizo un análisis lineal y se consideró las no linealidades asociadas a la geometría del modelo. Las variables incluidas en el modelado fueron el módulo de elasticidad y la razón de Poisson. Se aplicó una carga monótamente creciente de 1N en la superficie lingual de la corona con una inclinación de 45º. Los esfuerzos de von Mises fueron determinados. Resultados: el análisis de elementos finitos indicó que la distribución de los esfuerzos generados en el diente modelado con los postes disminuyó significativamente,de acuerdo con una relación inversamente proporcional al módulo de elasticidad del material. En el modelo con implante, los esfuerzos se concentraron en la zona cervical y en el implante mismo. Conclusiones: con las limitantes de este estudio, se encontróque existen variaciones marcadas con respecto a la distribución de los esfuerzos en las tres alternativas de retención, donde un sistema con varios componentes de diferente rigidez es cargado, el elemento más rígido resiste los mayores esfuerzos sin distorsión.

Introduction: the purpose of this study was to analyze the stress distribution among three retention alternativesused in a three unit fixed partial prosthesis, using the Finite Element Analysis (FEA). Methods: three tridimensional FEA modelsof the upper anterior area, restored with a cast post, another with a prefabricated post and the third one with an implant, were prepared. The models of the restored area consisted of trabecular bone, cortical bone, periodontal ligament, gingival, root, gutta-percha, resin luting cement, post, composite resin core (for prefabricated posts), metallic core and metal ceramic crown.The post materials considered for analysis were a noble casting alloy and fiber glass. The posts were cemented with resin luting cement. A lineal analysis was carried out and the nonlinearities associated with the geometry of the model, were considered. The variables included in the model were the modulus of elasticity and Poisson´s ratio. An increasing load of 1N was applied on the lingual surface of the crown with an inclination of 45°. Von Mises stress were then calculated. Results: the Finite Element Analysisshowed that the distribution of stresses generated on the tooth modeled with posts, decreased significantly, in accordance with an inverse proportional relation with the modulus of elasticity of the material. In the implant model, the stresses concentrated on the cervical area and on the implant itself. Conclusions: within the limitations of this study, it was found that that there were marked differences in relation with the stress distribution among the three retention alternatives, where the system with different rigidity components is loaded, the most rigid element is capable of resisting the highest stress without distortion.