Diseño de un Seminario/Laboratorio asistido por ordenador para el estudio de procesos de foto-descontaminación de efluentes gaseosos en MATLAB®

El proyecto ha desarrollado un seminario/laboratorio asistido por ordenador que incluye la simulación de un sistema de reacción para la descontaminación de corrientes gaseosas y la validación experimental a partir de medias experimentales del flujo de fotones en el sistema lámpara-reactor. Ha sido diseñado como actividad práctica de la asignatura “Ingeniería Ambiental” del Grado en Ingeniería Química de la Universidad de Granada. Estará relacionado con los contenidos que se desarrollan en el “Bloque 2: Contaminación de corrientes gaseosas” a partir del estudio y diseño de un sistema de reacción foto-catalítico para la eliminación de contaminantes en fase gas; promoviendo el desarrollo de competencias básicas, generales y específicas de la asignatura recogidas en la memoria verificada del grado. Se ha realizado el diseño completo de la actividad generando una gran variedad de material didáctico entre los que se encuentran: presentaciones/diapositivas vinculadas a la actividad, guías de desarrollo del seminario, código desarrollado en MATLAB®, guion de prácticas para la validación experimental, etc. Estos han sido diseñados para que puedan ser aplicados en formato presencial, híbrido (presencial/no presencial) o completamente virtual. Se han diseñado varias plantillas de trabajo para el estudiantado que están asociadas a distintos niveles de dificultad, lo que permitirá una relativa flexibilidad para su aplicación en otras asignaturas del Grado en Ingeniería Química. La parte final del seminario incluye la validación experimental del modelo a partir de mediciones básicas de propiedades ópticas del equipo de reacción, de modo que este proyecto ha incluido también tareas donde se han diseñado estas actividades experimentales

Recent progress in the quantitative assessment and interpretation of photoactivity

The development of the photo-catalysis field is limited by a deficient quantitative assessment of photo-activity. The interplay between mass and momentum transport together with radiative transfer phenomena taking place at any photo-catalytic reaction or process makes complex such quantitative assessment. To reach this goal, the review studies the measurement, meaning, and analysis of three types of observables. The first family of observables has the reaction rate and closely connected observables as the turnover frequency as central pieces. The second family owns the so-called efficiency observables, starting from the photonic yield and quantum efficiency of the reaction and ending in the global efficiency of the process. Finally, the review studies kinetic constant observables. The contribution focusses on most rencet contribution analyzing these observables in terms of their (adequate) measurement conditions and physico-chemical interpretation, in order to unveil their full potential in the context of the photo-catalysis field.MCIN/AEI PID2019-105490RB-C31ERDF A way of making EuropeEuropean CommissionConsejo Nacional de Ciencia y Tecnologia (CONACyT) SENER-CONACyT 117373UGR PPJIA2019-0

Er-W codoping of TiO2-anatase: structural and electronic characterization and disinfection capability upon UV, visible, and near-IR excitation

The codoping of the anatase structure with tungsten and erbium was carried out using a microemulsion preparation procedure. Tungsten and erbium single doped and pure anatase nanomaterials were also prepared. The corresponding solids were characterized using X-ray diffraction, surface area, transmission electron microscopy, X-ray photoelectron and absorption (X-ray near-edge and extended X-ray absorption) spectroscopies as well as UV–vis and photoluminescence spectroscopies. Results provided a complete structural and electronic characterization of the solids, showing the unique features generated by the copresence of tungsten and erbium at substitutional positions of the anatase structure. The disinfection capability of these single and codoped TiO2-based materials was tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria and under ultraviolet, visible and near infrared light excitations. The ErW-anatase solid presents significant photoactivity in the elimination of both microorganisms in the whole UV–vis-nearIR range of excitation wavelengths. The biocidal results were interpreted with the help of a kinetic modelling of the experiments and correlated with results from the physico-chemical characterization of the samples and from an electron paramagnetic resonance and optical study of the radicals species produced under illumination. This procedure indicates a different physical origin of the photoactivity for light excitation above and below ca. 500 nm

Thermo-photo degradation of 2-propanol using a composite ceria-titania catalyst: Physico-chemical interpretation from a kinetic model

This work describes a study carried out to construct and determine a kinetic formalism for the gas-phase degradation of 2-propanol using a combined thermo-photo based process. Outstanding catalytic performance was observed for a composite ceria-titania system with respect its parent ceria and titania reference systems. Thermo-photo as well as parallel photo- and thermal-alone experiments were carried out to interpret catalytic behavior. The kinetic experiments were conducted using a continuous flow reactor free of internal and external mass-heat transfer and designed using a Box-Behnken formalism. The kinetic expression developed for the thermo-photo degradation process explicitly includes the effect of the photon absorption in the reaction rate and leads to a mathematical formula with two components having different physico-chemical nature. This fact is used to settle down a fitting procedure using two steps (two separated experimental sets of data concerning temperature, light intensity, oxygen, water and/or 2-propanol concentrations) with, respectively, four and three parameters. The kinetic formalism was validated by fitting the experimental data from these two independent experiments, rendering a good agreement with the model predictions. The parameters coming from the kinetic modelling allow an interpretation of the catalytic properties of the ceria-titania catalyst, quantifying separately its enhanced performance (with respect to its parent systems) in the photonic and thermal components for the process. The procedure is applicable to a wide variety of thermo-photo processes in order to contribute to the understanding of their physical roots

Enhancing photocatalytic performance of TiO2 in H2 evolution via Ru co-catalyst deposition

A series of ruthenium catalysts supported into pure anatase titania were tested in the photo-production of hydrogen from methanol:water mixtures under UV and visible illumination conditions. Catalysts containing 1, 2, 3 and 5 wt.% of ruthenium were subjected to a characterization study with the help of X-ray diffraction, Raman, X-ray photoelectron spectroscopy, photoluminescence, morphology as well as scanning and transmission electron microscopy. Through the measurement of the optical properties of the suspension of the catalysts and the hydrogen photo-production reaction rate we calculate the true quantum efficiency. Optimum activity is presented by the catalyst with a 3 wt.% of Ru component, which shows quantum efficiency values of ca. 3.1 and 0.6% under, respectively, UV and visible light illumination. Careful examination of the physico-chemical properties of the solid allows to establish a correlation between the ruthenium surface exposed and the quantum efficiency. The implications of such result to justify chemical activity of the ruthenium supported samples are discussed both for UV and visible illumination conditions

Laboratory-Scale Optimization of Celestine Concentration Using a Hydrocyclone System

A pilot hydrocyclone plant was used to concentrate medium-grade celestine ore (67% celestine) from the Montevive deposit in Granada (Spain) by using a dense media concentration (DMS) process. To optimize the concentration process, several types of heavy minerals (coarse, fine C40 ferrosilicon and/or magnetite) were used to prepare a dense media with a constant density of 3.0 kg/L. Then, the dense media (loaded with run-of-mine celestine mineral) was fed into the hydrocyclone system. The mineral was then separated into two streams, the first containing the mineral fractions that float (over stream) and the second containing fractions that sink (under stream) in the dense media. Next, the heavy minerals (ferrosilicon and/or magnetite) were recovered from the dense media using magnetic separation. The celestine mineral recovered from each stream was divided into two fractions with particles size above or below 250 m to study the effect of the mineral particle size on the separation process. Their mineral composition was quantified by X-ray diffraction (XRD) using the Rietveld method. The celestine is preferentially concentrated in the under stream in the mineral fraction with particles larger than 250 m (up to 90% celestine). The optimum results (highest % of celestine) were obtained after desliming and using the ferrosilicon C40 medium, which has the smallest particle size (<40 m) of all media used. The results of this study show that medium-grade celestine mineral accumulated in the mine tailings can be efficiently concentrated using a DMS process, which could help in making mine operations more sustainable and eco-friendlier.CNT 5589 (University of Granada)MineTheGap (European Union) CELABDEN PROJEC

Bimetallic Pt-Pd co-catalyst Nb-doped TiO2 materials for H2 photo-production under UV and Visible light illumination

In this work we synthesized a series of binary PtPd co-catalysts supported on a Nb-doped TiO2 support. The catalytic solids and corresponding monometallic reference systems are characterized using X-ray diffraction, X-ray photoelectron, and UV–vis spectroscopies, together with microscopy and porosimetry tools. Such characterization was able to show the formation of PtPd alloy particles in the bimetallic catalysts. The mono and bimetallic TiO2-based powders were tested in the photo-production of hydrogen from methanol:water mixtures under UV and visible illumination conditions. Analysis of catalytic properties was carried out through the measurement of the optical properties of the materials and the calculation of the true quantum efficiency parameter. Results indicate that the PtPd co-catalysts have superior performance that the Pt and Pd monometallic counterparts both under UV and visible illumination conditions. Optimum performance was achieved with a material having a Pt:Pd 1:1 atomic ratio. A remarkable increase in the use of the visible range and thus in sunlight utilization is achieved with the 1:1 Pt:Pd bimetallic system with respect to the monometallic counterparts. The evolution of the bimetallic co-catalysts under reaction conditions as well as their key properties to interpret photo-activity were analyzed with the help of the above mentioned techniques as well as photoluminescence spectroscopy and an in-situ infrared analysis of the materials under reaction conditions. Results point out the critical role that both PtPd alloying and the metal-support interface play in the reaction

Improving electrochemical hydrogen evolution of Ag@CN nanocomposites by synergistic effects with α-rich proteins

A graphitic carbon nitride nanostructure has been successfully functionalized by incorporation of different silver contents and subsequent modification with an α-rich protein, namely hemoglobin. Mechanochemistry has been employed, as an efficient and sustainable procedure, for the incorporation of the protein. A complete characterization analysis has been performed following a multitechnique approach. Particularly, XPS data exhibited considerable differences in the C 1s region for the Hb/xAg@CN, ensuring the successful protein anchorage on the surface of the graphitic carbon nitride-based materials. The as-synthesized nanomaterials delivered impressive performance toward hydrogen evolution reactions with an overpotential of 79 mV at a current density of 10 mA/cm2 for Hb/20Ag@CN nanohybrids, which is comparable with the most efficient HER electrocatalysts reported in the literature. The outstanding HER properties were associated with the unique synergistic interactions, quantitatively measured, between AgNPs, Hb tertiary architecture, and the graphitic carbon nitride networks

Boosted Activity of g-C3N4/UiO-66-NH2 Heterostructures for the Photocatalytic Degradation of Contaminants in Water

The combination of graphitic carbon nitride and the metal-organic framework UiO-66-NH2 has been developed with the aim to enhance the photocatalytic activity of pure semiconductors. Different proportions of g-C3N4 and UiO-66-NH2 were combined. Complete characterization analysis of the resulting photocatalytic materials was conducted, including N-2 adsorption isotherms, XRD, FTIR, STEM-EDX microscopy, DRS-UV-visible, and photoluminescence. The photocatalytic activity was tested in an aqueous solution for the removal of acetaminophen as the target pollutant. From the obtained results, less than 50% of UiO-66-NH2 incorporated in the g-C3N4 structure enhanced the photocatalytic degradation rate of both bare semiconductors. Concretely, 75% of g-C3N4 in the final g-C3N4 /UiO-66-NH2 heterostructure led to the best results, i.e., complete acetaminophen elimination initially at 5 mg.L-1 in 2 h with a pseudo-first order rate constant of ca. 2 h(-1). The presence of UiO-66-NH2 in the g-C3N4 enhanced the optoelectronic properties, concretely, the separation of the photo-generated charges was improved according to photoluminescence characterization. The better photo-absorption uptake was also confirmed by the determination of the quantum efficiency values of the heterostructure if compared to either pure g-C3N4 or UiO-66-NH2. This photocatalyst with the best activity was further tested at different pH values, with the best degradation rate at a pH close to the pH(pzc) similar to 4.15 of the solid. Sequential recycling tests demonstrated that the heterostructure was stable after five cycles of use, i.e., 15 h. A high contribution of photo-generated holes in the process of the degradation of acetaminophen, followed marginally by superoxide radicals, was suggested by scavenger tests.University of Granada PPJIA2019-09 PPJIA2021-3

Ruthenium deposited onto graphitic carbon modified with boron for the intensified photocatalytic production of benzaldehyde

The selective oxidation of added-value aromatic alcohols into aldehydes of high interest via photocatalysis has been postulated as a green and competitive oxidative reaction at mild conditions. This work is focused on the design of a tertiary graphitic carbon nitride (g-C3N4) based photocatalysts competitive for the photocatalytic production of benzaldehyde in an aqueous solution. The polymeric g-C3N4 has been modified in an easy one-pot green synthesis scheme, with the incorporation of boron in the polymeric structure and the deposition of ruthenium nanoparticles. The Ru ratio within 0.5–4% was assessed. The photocatalysts were fully characterized (XRD, FTIR, XPS, N2 isotherms, DRS-UV–visible, and PL) and the photocatalytic activity was assessed in the oxidation of benzyl alcohol to benzaldehyde in an aqueous solution. The incorporation of boron enhanced the selectivity towards benzaldehyde due to enhanced separation charges suggested by the photoluminescence technique; whereas ruthenium improved the reaction rate of the alcohol, affecting negatively the selectivity though. The sample containing 1% of Ru was selected as the optimum in terms of selectivity. The relative contribution of the involved reactive oxidant species was assessed by chemical scavenger tests, highlighting the contribution of the photo-generated holes followed by O2•‾. The analysis of the band’s alignment of the g-C3N4 before the modification with boron and ruthenium supports the enhancement by rising the redox potential of the holes released in the valence band