Evaluación experimental y matemática de modelos de adsorción molecular para contaminantes orgánicos en partículas de TiO2-P25

Abstract In this work we evaluated conventional models based on adsorption isotherms of L2 type for organic compounds: DCA, phenol and 4-chlorophenol over TiO2-P25 particles to different operational conditions. The models studied were Langmuir-Hinshelwood, Redlich-Petersen and Toth because these models can be applied as possible equations to improve the description of the reaction rate mechanism based on hydroxyl radical attack, and the degradation using heterogeneous photocatalysis. Finally the models were compared with experimental data for determination of the more appropriate isotherm. L-H model was the more appropriate and the results were high effective in the prediction of experimental data. Resumen Se evaluaron modelos convencionales de adsorción molecular basados en isotermas del tipo L2 para compuestos orgánicos ácido dicloroacético, fenol y 4-clorofenol sobre partículas de TiO2-25 a diferentes condiciones de operación. Los modelos estudiados fueron Langmuir-Hinshelwood, Redlich-Petersen y Toth puesto que estos modelos pueden ser aplicados como posibles ecuaciones para mejorar la descripción de los mecanismos de velocidad de reacción basados en ataque de radicales hidroxilo y degradación usando fotocatálisis heterogénea. Los modelos fueron comparados con datos experimentales para determinar la isoterma más adecuada. El modelo L-H fue el mas apropiado y los resultados fueron de alta efectividad en la predicción de los datos experimentales

Implementación de un curso MOOC aplicando la metodología MIA® (Mindfulness Into Action), mediante plataforma EDJET para el Instituto Mia®, Ibarra, Ecuador

Implementar un curso MOOC aplicando la metodología MIA® (Mindfulness Into Action) mediante la plataforma Edjet para el Instituto MIA® Ibarra Ecuador.El proyecto nace de la necesidad de virtualizar y dar a conocer el uso de nuevas herramientas tecnológicas para realizar metodologías de investigación y desarrollo personal. En este caso se construyó una plataforma MOOC Massive Open Online Course para virtualizar el proceso MIA® (Mindfulness Into Action), el mismo que fue desarrollado en Columbia University. MIA® es un proceso de desarrollo cognitivo que combina prácticas organizacionales y técnicas indígenas, con el fin de construir de forma sistémica un proceso de investigación acción, en una plataforma virtual. Compartir el desarrollo de esta metodología tiene como principal objetivo alcanzar a más usuarios, puesto que hoy en día las tecnologías de machine learning virtual son las plataformas más comerciales a nivel mundial para el aprendizaje. Lo que se traduce en varias ventajas de desarrollo como reducción de los costos de aplicación del proceso MIA y tiempo que conlleva el análisis de la información en una forma cualitativa y cuantitativa. Además, se utilizó tres metodologías para el desarrollo de la presente tesis, que son la metodología DICREVOA 2.0 que nos permitió virtualizar la metodología MIA a través de los objetos de aprendizaje. Y XP nos permitió el desarrollo del sistema de evaluación y seguimiento de los participantes.Ingenierí

Comprehensive kinetics of the photocatalytic degradation of emerging pollutants in a led-assisted photoreactor. S-metolachlor as case study

Although the potential and beneficial characteristics of photocatalysis in the degradation of a good number of emerging pollutants have been widely studied and demonstrated, process design and scale-up are restrained by the lack of comprehensive models that correctly describe the performance of photocatalytic reactors. Together with the kinetics of degradation reactions, the distribution of the radiation field in heterogeneous photocatalytic systems is essential to the optimum design of the technology. Both the Local Volumetric Rate of Photon Absorption (LVRPA) and the Overall Volumetric Rate of Photon Absorption (OVRPA) help to understand this purpose. This work develops a Six-lux radiation absorption-scattering model coupled to the Henyey-Greenstein scattering phase function to evaluate the LVRPA profile in a LED-assisted photocatalytic reactor. Moreover, the OVRPA has been calculated and integrated into the kinetic equation, accounting for the influence of the radiation distribution on the reaction rate. The model has been validated with experimental data for the degradation of S-Metolachlor (MTLC), and the set of operating variables that maximize the reactor performance, 0.5 g/L of TiO2 P25 and pH 3, has been determined.This research was funded by the Spanish Ministry of Science, Innovation, and Universities (Grant Numbers: RTI2018-099407-B-I00 and RTI2018-093310-B-I00) (MCIU/AEI/FEDER, UE)

Impact of photocatalyst optical properties on the efficiency of solar photocatalytic reactors rationalized by the concepts of initial rate of photon absorption (IRPA) dimensionless boundary layer of photon absorption and apparent optical thickness

The concepts of “initial rate of photon absorption” (IRPA), “dimensionless boundary layer of photon absorption” and “apparent optical thickness (τapp)” are presented to evaluate the radiative transfer phenomena in solar, slurry, planar, photocatalytic reactors. The radiation field produced by suspensions of TiO2 and goethite, two photocatalysts with profoundly different optical properties used in heterogenous photocatalysis and heterogeneous photo-assisted Fenton reactions, was determined by the six-flux radiation absorption-scattering model coupled to the Henyey-Greenstein scattering phase function (SFM-HG). The concept of IRPA, defined by the differentiation at the local volumetric rate of photon absorption (LVRPA) at the reactor window boundary, is proposed as a new approach to determine the impact of catalyst loading and optical properties on the extinction of light inside a photoreactor. The IRPA showed that the extinction of light follows a second order dependency on the photocatalyst concentration while the impact of the optical properties can be expressed by a decoupled function (Ψ function). The Ψ function increased with photocatalyst concentration and approached a maximum at the same optimal photocatalyst concentration determined from the analysis of the total rate of photon absorption (TRPA) in the reactor. The analysis of TRPA and boundary layer of photon absorption redefined here in dimensionless form, as a function of τapp, determined that the most efficient rate of radiation absorption in solar powered planar reactors occurs at τapp = 4.1–4.4, with approximately 10% of the reactor width under darkness. τapp is a similarity dimensionless parameter exclusively derived from the SFM approach, which clusters the effects of photocatalyst loading, reactor dimension and photocatalyst optical properties, providing an ideal parameter for designing and scaling photocatalytic reactors operated with any kind of photocatalytic material

Boundary Layer of Photon Absorption Applied to Heterogeneous Photocatalytic Solar Flat Plate Reactor Design

This study provides information to design heterogeneous photocatalytic solar reactors with flat plate geometry used in treatment of effluents and conversion of biomass to hydrogen. The concept of boundary layer of photon absorption taking into account the efficient absorption of radiant energy was introduced; this concept can be understood as the reactor thickness measured from the irradiated surface where 99% of total energy is absorbed. Its thickness and the volumetric rate of photons absorption (VRPA) were used as design parameters to determine (i) reactor thickness, (ii) maximum absorbed radiant energy, and (iii) the optimal catalyst concentration. Six different commercial brands of titanium dioxide were studied: Evonik-Degussa P-25, Aldrich, Merck, Hombikat, Fluka, and Fisher. The local volumetric rate of photon absorption (LVRPA) inside the reactor was described using six-flux absorption-scattering model (SFM) applied to solar radiation. The radiation field and the boundary layer thickness of photon absorption were simulated with absorption and dispersion effects of catalysts in water at different catalyst loadings. The relationship between catalyst loading and reactor thickness that maximizes the absorption of radiant energy was obtained for each catalyst by apparent optical thickness. The optimum concentration of photocatalyst Degussa P-25 was 0.2 g/l in 0.86 cm of thickness, and for photocatalyst Aldrich it was 0.3 g/l in 0.80 cm of thickness

Coupling the six flux absorption-scattering model to the Henyey-Greenstein scattering phase function: Evaluation and optimization of radiation absorption in solar heterogeneous photoreactors

© 2016 Elsevier B.V.Robust and practical models describing the radiation field in heterogeneous photocatalytic systems, used in emerging environmental, photochemical and renewable energy applications, are fundamental for the further development of these technologies. The six-flux radiation absorption-scattering model (SFM) has shown to be particularly suitable for the modeling of the radiation field in solar pilot-plant photoreactors. In this study, the SFM was coupled to the Henyey-Greenstein (HG) scattering phase function in order to assemble the model with a more accurate description of the scattering phenomenon provided by this phase function. This new version of SFM, named as SFM-HG, was developed through fitting the Local Volumetric Rate of Photon Absorption (LVRPA) determined in a flat photoreactor to the "pseudo-experimental" LVRPA calculated by a Monte Carlo (MC) approach, which included the HG expression. As a result, simple mathematical correlations describing the SFM-HG scattering probabilities as function of the HG scattering parameter were determined. The SFM-HG was validated through a comparison with the MC model predictions of the Total Rate of Photon Absorption (TRPA) in the slab photoreactor. A RMSE% of approximately 5% demonstrated satisfactory agreement between the models. The SFM-HG was further applied to evaluate the impact of selected scattering phase functions on the absorption of radiation in solar photoreactors, operated with commercial TiO2 photocatalyst. The results have established that, the apparent optical thickness, τapp (or τapp,max for tubes) a parameter derived from the SFM approach, is the most appropriate for the design and optimization of photocatalytic reactors. This parameter is insensitive to scattering albedos and phase functions. CPC, tubular and flat-plate photoreactors should be designed with τapp,max = 12, τapp,max = 7 and τapp = 4.5 respectively

Mathematical Analysis of Discontinuous Rectification Columns at Pilot Scale Based on the Continuous Stable States Concept and MESH Equations

Mathematical analysis and simulation of a discontinuous rectification column was performed using an operational strategy during the start-up before reaching a pseudo-stable state in discontinuous operation. The mathematical model was formulated focusing on the equilibrium state (ES) and implementing MESH equations (M: Mass balance, E: Equilibrium thermodynamics, S: Stoichiometry relations, H: Enthalpy or heat balance) to provide solutions using the Thomas method and the Wang-Henke algorithms internally coupled to the Fourth Order Runge-Kutta method. The results were validated with experimental data from a distillation column at a pilot scale using an ethanol-water system with an equilibrium behavior described by the UNIQUAC Functional-group Activity Coefficients (UNIFAC) and Predictive Soave-Redlich-Kwong (PSRK) thermodynamic models with a global error of 1.84%. The molar ethanol concentrations presented deviations from the mathematical model predictions from 1.51% to 0.02%, with a global mean error of 0.48%. A mean error of 0.055% was obtained for the temperature profile of the column, thus demonstrating the effectiveness of the solution and its convergence capacity. The solution based on the Thomas method and the Wang-Henke algorithms coupled to the Runge-Kutta method made it possible to describe the behavior and variables of all stages of the distillation column. Operation at total reflux from start-up avoids wasting product and allows for the stabilization of the state variables, such as temperature and molar composition

A novel prototype offset multi tubular photoreactor (OMTP) for solar photocatalytic degradation of water contaminants

© 2018 Elsevier B.V. The design and operation of a new solar photoreactor prototype named Offset Multi Tubular Photoreactor (OMTP) is presented. The OMTP advances over the compound parabolic collector (CPC) photoreactor, which is one of the most efficient design for large-scale solar detoxification of water and wastewater. The OMTP design is based on a simple modification of the common CPC and included a supplementary set of tubes in the space occupied by the axes of intersection of the CPC reflective involutes. This new reactor configuration increased the irradiated reactor volume by 79% and the fluid residence time by up to 1.8-fold in comparison to the CPC, for the same solar irradiated area (footprint). The model parameters used for comparing and scaling the OMPT and CPC were β (reactor volume/total volume), α (area of absorption/total volume), α g (physical area/total volume), degradation efficiency η α per unit area, and the operating volume. The total solar energy absorbed in the reactors (1.74 m 2 footprint) was 15.17 W for the CPC and 21.86 W for the OMTP, which represents an overall gain of 44% for the latter. The performance of the OMTP and CPC were compared at the same value of solar exposure, β of 0.3 with optimal photocatalyst loading of 0.25 g/L titanium dioxide (TiO 2 P25). The degradation efficiencies of methylene blue, dichloroacetic acid, 4-chlorophenol (120 ppm initial concentration) in the OMTP were up to 81%, 125%, 118% and 242% higher, respectively, in comparison to the CPC after 8000 J/m 2 of accumulated solar energy. The OMTP should outperform the CPC in environmental and renewable energy applications of solar heterogeneous photocatalysis

Scale-Up and Optimization for Slurry Photoreactors

Several aspects of scale-up and optimization of heterogeneous photocatalytic reactors are detailed in the following chapter. The relevance of the dimensionless numbers, the critical factors of the photoreactor design, and the optimization methods are explored from an engineering point of view. The apparent optical thickness is the most crucial dimensionless parameter for photoreactor design and optimization; therefore, the study will be more focused on this topic. Moreover, a real case for a commercial application of the solar photocatalysis will be presented in this chapter. This full-scale plant is currently operating as an industrial wastewater treatment plant in a flexographic company located in Cali, Colombia

Synthesis of Mg-Al layered double hydroxides by electrocoagulation

Recently, layered double hydroxides (LDHs) have attracted much consideration due to their versatility and easily manipulating properties and their potential applications such as anion exchangers, support of catalysts, flame retardants, biomedical drug delivery. A novel method for the in-situ preparation in situ of LDHs, using electrocoagulation (EC) processes was developed, the EC process was performed under two different conditions, at 5 mA m−2, changing polarity of the electrodes to find out the composition that leads to LDHs generation. The final product was characterized using XRD, BET and FTIR techniques. This method presented the following advantages: (1) Simultaneously LDHs synthesis and wastewater treatment by ion removal; (2) Polarity control allows to manipulate the M2+/M3+molar ratio, LDHs properties and its potential applications; (3) The method spent less time to carry out the synthesis and; (4) it did not need complicated solid-liquid separation processes