Intensificación del proceso electroquímico para la remoción de cromo en residuos líquidos

173 páginas. Doctorado en Ingeniería de Procesos.El cromo es un metal comúnmente utilizado en la industria galvanoplástica, la cual genera aguas de enjuague que contienen concentraciones de cromo hexavalente por encima de las permisibles por la regulación ambiental. Varias alternativas de tratamiento se han propuesto para atacar este problema, de donde destacan los métodos electroquímicos. Entre estos últimos, un proceso atractivo es el que utiliza electrodos de hierro, los cuales son fuente para la generación electroquímica in situ del agente reductor, que químicamente reduce al cromo en el seno del líquido, de su estado hexavalente a trivalente. El efluente, pasa a un tanque de mezclado para propiciar la precipitación de los metales en hidróxidos metálicos, mediante el incremento del pH del medio, con la finalidad de separarlos del agua tratada. En este trabajo se presentan distintas estrategias para intensificar este proceso de tratamiento, con la finalidad de mejorar el desempeño hidrodinámico del reactor electroquímico y la etapa de precipitación. Para la evaluación del comportamiento de los procesos, tanto en el reactor electroquímico como en el de precipitación, se realizaron pruebas experimentales en reactores de mezcla completa y de jarras, las cuales se complementaron con estudios mediante la dinámica computacional de fluidos, para integrar la información del desempeño de los procesos bajo los diferentes escenarios probados. El capítulo dos detalla el estudio realizado mediante herramientas de dinámica computacional de fluidos al reactor electroquímico de anillos rotatorios, el cual ha mostrado altas eficiencias de remoción de cromo hexavalente en aguas contaminadas. Esta parte del proyecto da a conocer cuál es el enfoque de modelado más apropiado para simular la hidrodinámica que se desarrolla dentro del reactor. Se realiza la comparación de los resultados predichos por tres variantes del modelo de turbulencia κ-ε (standard, RNG y realizable) acoplado al modelo de múltiples marcos de referencia para simular la rotación del electrodo. También se evalúa el efecto de la posición de las fronteras del marco de referencia rotacional respecto a las fronteras del marco de referencia estacionario. Se demuestra que la predicción con el modelo κ−ε realizable en conjunto con la posición a 0° genera los resultados con mayor acercamiento a las mediciones experimentales de tiempo de mezclado obteniendo un 6% de error. En el capítulo tres se muestran los resultados de la incorporación de una novedad, la cual consiste en un reactor equipado con el electrodo estático de electro-deflectores agitado por dos impulsores de alabes inclinados, conocido como PBT. Los resultados de esta modificación se comparan respecto a los obtenidos con el desempeño del reactor electroquímico equipado con el electrodo dinámico de anillos rotatorios. La comparación se realiza de forma teórica para evaluar sus diferencias en cuanto a su desempeño hidrodinámico, y experimental para conocer su eficiencia frente a la reducción de cromo hexavalente. Para realizar la comparación, los reactores se operaron a la misma velocidad de agitación y al mismo número de Reynolds. Los resultados del análisis hidrodinámico muestran que el arreglo de electro-deflectores estáticos junto con el par de impulsores permite mejorar el tiempo de mezclado en 36%, incrementando la eficiencia hidráulica en 85% cuando el reactor se opera al mismo número de Reynolds. Se evidencia que la capacidad de circulación del reactor afecta directamente la tasa de reducción de cromo hexavalente, ya que los tiempos de tratamiento tienen una tendencia parecida a los tiempos de circulación axial. También se muestra que hay una reducción del consumo energético de al menos un 21% cuando el reactor es equipado con los electro-deflectores y el sistema de agitación de dos impulsores. En el capítulo cuatro se evalúan las condiciones de operación del reactor electroquímico, como son: configuración geométrica del electrodo, velocidad de agitación e intensidad de corriente. Para evaluar el cambio en la configuración del electrodo se utiliza el electrodo de anillos estáticos y electro-deflectores. Al operar el electrodo con anillos estáticos también se evalúa la necesidad de incorporar deflectores convencionales. Los sistemas de agitación del reactor están compuestos por dos impulsores PBT, de los cuales también se evalúa la separación entre ellos. Al realizar las simulaciones se consideró la interacción de la interfase líquido-gas. Los resultados revelan que por la posición de los impulsores es necesario tomar en cuenta en el modelo la interacción líquido aire para obtener una predicción más realista del patrón de flujo en la configuración de electro-deflectores. Resultado de los estudios, se obtuvo que la configuración con menor consumo energético fue la de los electro-deflectores con una separación entre impulsores igual a su diámetro pues sus características geométricas e hidrodinámicas le permiten ser más eficiente. En este sistema se exploró el efecto de la velocidad de agitación y de la intensidad de corriente. La velocidad de agitación aumenta la tasa de reducción de cromo hexavalente, hallando su límite en 300 rpm. En esta velocidad de agitación se exploró el efecto de la intensidad de corriente, de donde se encuentra una dependencia lineal del consumo energético del reactor respecto a esta variable en el rango evaluado. En el capítulo cinco se estudia la etapa de precipitación. Los estudios se realizan en un sistema de jarras agitado con dos tipos de impulsores, uno radial y otro axial. Se realiza la evaluación del efecto del pH al que se ajusta el efluente para realizar la precipitación en los valores de 4, 6, 7 y 9. Los resultados muestran que después de precipitar el agua tratada a un pH = 9.0, se obtiene un clarificado con pH neutro y se logran precipitar todas las especies. Se evalúa también el ambiente hidrodinámico de las jarras de forma experimental y numérica, determinando que el impulsor radial disipa mayor energía turbulenta respecto al impulsor axial. Por lo anterior, el impulsor axial propicia un ambiente hidrodinámico favorable para el desarrollo de los flóculos, lo que se traduce en velocidades de sedimentación mayores con respecto a las alcanzadas cuando la jarra se opera con el impulsor radial. Además, el impulsor axial consume solo el 50% de la energía que consume el impulsor radial.Chromium is a metal commonly used in the electroplating industry, which generates rinsing water containing hexavalent chromium concentrations above those allowed by environmental regulations. Several treatment alternatives have been proposed to attack this problem, among which electrochemical methods stand out. Among the latter, an attractive process is the one that uses iron electrodes, which are the source for the in situ electrochemical generation of the reducing agent, which chemically reduces the chromium in the liquid from its hexavalent to its trivalent state. The effluent is passed to a mixing tank to promote the precipitation of the metals into metal hydroxides by increasing the pH of the medium in order to separate them from the treated water. In this work, different strategies are presented to intensify this treatment process in order to improve the hydrodynamic performance of the electrochemical reactor and the precipitation stage. To assess the processes performance, in both systems, the electrochemical reactor and in the precipitation reactor, experimental tests were carried out in stirred tank reactors and jars test, which were complemented with studies using computational fluid dynamics to integrate the information on the performance of the processes under the different scenarios tested. Chapter two details the study carried out using computational fluid dynamics tools on the rotating rings electrochemical reactor, which has shown high removal efficiencies of hexavalent chromium in pollulet water. This part of the project shows the most appropriate modeling approach to simulate the hydrodynamics inside the reactor. Comparison of the results predicted by three variants of the κ-ε turbulence model (stadard, RNG and realizable) coupled to the multi-reference frame model to simulate the electrode rotation is performed. The effect of position of the rotational reference frame boundaries relative to the stationary reference frame boundaries is also evaluated. It is shown that the prediction with the κ-ε realizable model in conjunction with the position at 0° generates the results with the closest approach to the experimental mixing time measurements obtaining a 6% error. Chapter three shows the results of the incorporation of a novelty, which consists of a reactor equipped with the static electrode of electro-baffles agitated by two inclined vane impellers, known as PBT. The results of this modification are compared with those obtained with the performance of the electrochemical reactor equipped with the dynamic rotating ring electrode. The comparison is made theoretically to evaluate their differences in terms of hydrodynamic performance, and experimentally to know their efficiency against the reduction of hexavalent chromium. For the comparison, the reactors were operated at the same stirring speed and Reynolds number. The results of the hydrodynamic analysis show that the arrangement of static electro-baffles together with the pair of impellers improves the mixing time by 36%, increasing the hydraulic efficiency by 85% when the reactor is operated at the same Reynolds number. It is evident that the circulation capacity of the reactor directly affects the reduction rate of hexavalent chromium, since the treatment times have a similar trend to the axial circulation times. It is also shown that there is a reduction in energy consumption of at least 21% when the reactor is equipped with the electro-baffles and the two-impeller agitation system. In chapter four, the operating conditions of the electrochemical reactor are evaluated, such as: geometric configuration of the electrode, stirring speed and current intensity. To evaluate the change in the electrode configuration, the static ring electrode and electro-baffles are used. When operating the electrode with static rings, the need to incorporate conventional baffles is also evaluated. The reactor agitation systems are composed of two PBT impellers, of which the separation between them is also evaluated. In performing the simulations, the interaction of the liquid-gas interface was considered. The results reveal that due to the position of the impellers it is necessary to take into account the liquid-air interaction in the model to obtain a more realistic prediction of the flow pattern in the electro-baffles configuration. As a result of the studies, it was found that the configuration with the lowest energy consumption was the electro-baffles with a separation between impellers equal to their diameter, since its geometrical and hydrodynamic characteristics allow it to be more efficient. The effect of agitation speed and current intensity was explored in this system. The agitation speed increases the reduction rate of hexavalent chromium, finding its limit at 300 rpm. At this agitation speed, the effect of the current intensity was explored, from which a linear dependence of the reactor energy consumption on this variable was found in the range evaluated. In chapter five, the precipitation stage is studied. The studies are carried out in an agitated jar system with two types of impellers, one radial and the other axial. The evaluation of the effect of the pH at which the effluent is adjusted to perform precipitation at values of 4, 6, 7 and 9 is carried out. The results show that after precipitating the treated water at pH = 9.0, a clarified product with neutral pH is obtained and all species are precipitated. The hydrodynamic environment of the jars is also evaluated experimentally and numerically, determining that the radial impeller dissipates more turbulent energy than the axial impeller. Therefore, the axial impeller provides a favorable hydrodynamic environment for the development of flocs, which results in higher sedimentation velocities than those achieved when the jar is operated with the radial impeller. In addition, the axial impeller consumes only 50% of the energy consumed by the radial impeller.Investigación realizada con el apoyo del Programa Nacional de Posgrados de Calidad del Consejo Nacional de Ciencia y Tecnología (CONACYT)

Propuesta de un modelo para predecir el comportamiento de la operación de solubilización de residuos sólidos orgánicos

Uno de los retos en la aplicación de la digestión anaerobia para el tratamiento de residuos sólidos orgánicos son los pretratamientos que necesitan estos sustratos para ser solubilizados y metabolizados eficientemente por los microorganismos. La solubilización es una alternativa viable porque acorta los tiempos de retención en el digestor y no utiliza agentes químicos. El presente trabajo expone la propuesta de un modelo dinámico para predecir la solubilización de residuos de frutas y hortalizas (RFH), la cual es una de las etapas importantes pues de ello depende la cantidad de sustrato soluble provenientes de los RFH que se alimentará al reactor anaerobio. Se considera el sistema de solubilización adaptado a tres distintos escenarios de operación; lote, continuo, y mixto.One of the challenges in the application of anaerobic digestion for the treatment of organic solid waste is the pretreatments that these substrates need to be adequately metabolized by microorganisms. Solubilization is a viable alternative because it shortens retention times in the digester and does not use chemical agents. This work presents the proposal of a dynamic model to predict the solubilization stage, which is one of the important stages because the amount of nutrients in the organic solid waste that will be fed to the anaerobic reactor depends on it. The solubilization system is considered adapted to three different operation scenarios: batch, continuous, and mixed

PIV and dynamic LES of the turbulent stream and mixing induced by a V-grooved blade axial agitator

The hydrodynamic behavior of a turbulent flow and the mixing characteristics generated by a V-grooved axial impeller inside an agitated tank reactor were investigated both experimentally and numerically. Angle resolved Particle Image Velocimetry (PIV) techniques with an angular displacement Δθ = 5° have been applied and two aerodynamic planes along the blades were considered. PIV-based results were compared to those obtained by Large Eddy Simulation (LES), used with the dynamic Smagorinsky-Lilly sub-grid scale (SGS) model. Results showed the existence of distinctive recirculation zones in the aerodynamic planes, and new additional frequencies in the impeller stream, induced by the grooves. A decrease of mixing time of about 11% was obtained experimentally, consequence of the better suction induced by the grooved blades in the early stages of mixing. Mean velocities, vorticity, TKE obtained from LES showed a good agreement with the PIV-based results. The distributions of turbulence dissipation rate ε were similar to those obtained from PIV, however showing high under-predicted magnitudes

Allogeneic stem cell transplantation as a curative option in relapse/refractory diffuse large B cell lymphoma: Spanish multicenter GETH/GELTAMO study

Grupo Español de Trasplante Hematopoyético (GETH) and Grupo Español de Linfoma y Trasplante Autólogo (GELTAMO).We performed a retrospective multicenter study including 140 patients with relapsed/refractory (R/R) diffuse large B cell lymphoma (DLBCL) who underwent allogeneic hematopoietic stem cell transplantation (allo-SCT) from March 1995 to November 2018. Our objective was to analyze long term outcomes. Seventy-four percent had received a previous auto-SCT (ASCT) and the median number of lines pre-allo-SCT was 3 (range 1–9). Three year-event free survival (EFS) and overall survival (OS) were 38% and 44%, respectively. Non-relapse mortality (NRM) at day 100 was 19%. Cumulative incidence of grade III–IV acute graft versus host disease (GVHD) at day 100 was 16% and moderate/severe chronic GVHD at 3 years 34%. Active disease at allo-SCT (HR 1.95, p = 0.039) (HR 2.19, p = 0.019), HCT-CI ≥ 2 (2.45, p = 0.002) (HR 2.33, p = 0.006) and donor age >37 years (HR 2.75, p = 0.014) (HR 1.98, p = 0.043) were the only independent variables both for PFS and OS, respectively. NRM was significantly modified by HCT-CI ≥ 2 (HR 4.8, p = 0.008), previous ASCT (HR 4.4, p = 0.048) and grade III–IV acute GVHD on day 100 (HR 6.13, p = 0.016). Our data confirmed that allo-SCT is a curative option for patients with R/R DLBCL, displaying adequate results for fit patients with chemosensitive disease receiving an allo-SCT from a young donor

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

La Ciencia de Materiales en la Facultad de Química - UAEM

El libro se encuentra conformado por 13 capítulos que son resultados parciales de tesis de maestría y doctorado, escritos por estudiantes, por su comité de tutores y, en algunos casos, por los investigadores que colaboran con cada grupo disciplinario. Por ello, está dirigido a estudiantes de posgrado en Ciencia de Materiales, y de Ingeniería en Materiales del último año de la carrera.En 1996 dieron inicio los programas de Maestría y Doctorado en Ciencia de Materiales en la Facultad de Química de la Universidad Autónoma del Estado de México. Estos programas ofrecen a los estudiantes la formación académica y de investigación, a través del desarrollo de proyectos que incluyen la síntesis, modificación y el procesamiento de nuevos materiales para aplicaciones en medicina, óptica, construcción, catálisis, detección de sustancias volátiles, entre otras. En los últimos 3 años con el apoyo de estudiantes e investigadores, se logró concluir esta obra que da a conocer la importancia de sintetizar, caracterizar y aplicar materiales con base en sus propiedades.Secretaría de Educación Pública-Subsecretaría de Educación Superior-Dirección General de Educación Superior Universitaria. Número del convenio con la SEP: 2017-15-001-017

Global attitudes in the management of acute appendicitis during COVID-19 pandemic: ACIE Appy Study

Background: Surgical strategies are being adapted to face the COVID-19 pandemic. Recommendations on the management of acute appendicitis have been based on expert opinion, but very little evidence is available. This study addressed that dearth with a snapshot of worldwide approaches to appendicitis. Methods: The Association of Italian Surgeons in Europe designed an online survey to assess the current attitude of surgeons globally regarding the management of patients with acute appendicitis during the pandemic. Questions were divided into baseline information, hospital organization and screening, personal protective equipment, management and surgical approach, and patient presentation before versus during the pandemic. Results: Of 744 answers, 709 (from 66 countries) were complete and were included in the analysis. Most hospitals were treating both patients with and those without COVID. There was variation in screening indications and modality used, with chest X-ray plus molecular testing (PCR) being the commonest (19\ub78 per cent). Conservative management of complicated and uncomplicated appendicitis was used by 6\ub76 and 2\ub74 per cent respectively before, but 23\ub77 and 5\ub73 per cent, during the pandemic (both P < 0\ub7001). One-third changed their approach from laparoscopic to open surgery owing to the popular (but evidence-lacking) advice from expert groups during the initial phase of the pandemic. No agreement on how to filter surgical smoke plume during laparoscopy was identified. There was an overall reduction in the number of patients admitted with appendicitis and one-third felt that patients who did present had more severe appendicitis than they usually observe. Conclusion: Conservative management of mild appendicitis has been possible during the pandemic. The fact that some surgeons switched to open appendicectomy may reflect the poor guidelines that emanated in the early phase of SARS-CoV-2