Examinando por Autor "Marugán, J."

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Kinetic modeling of the first step of Mn2O3/MnO thermochemical cycle for solar hydrogen production
(Elsevier, 2012-12) Marugán, J.; Botas, J.A.; Molina, R.; Herradón, C.
This work reports the kinetic study of the first step of the Mn2O3/MnO thermochemical cycle for hydrogen production by water splitting. The reaction kinetics of Mn (III) oxide thermal reduction has been evaluated using dynamic thermogravimetric analysis at constant heating rate under nitrogen flow. This way the reaction rate can be described as a function of temperature and different kinetic models were fitted to the experimental data obtained from thermogravimetric experiments. A good fitting can be observed for each experiment, although a significant disparity in the values estimated for the Arrhenius parameters has been found (activation energies and pre-exponential factors). Unique values for the kinetic parameters have been calculated by application of a multivariate non-linear regression method for the simultaneous fitting of data from all the experiments carried out at different heating ramps. However, also in this case the values of the Arrhenius parameters are significantly different depending on the chosen kinetic equation. Optimal kinetic parameters have been finally calculated through the estimation of activation energy values by model-free isoconversional methods and using a rigorous multivariate nonlinear regression for the calculation of the model-dependant pre-exponential factors.
Optical density and photonic efficiency of silica-supported TiO2 photocatalysts
(ELSEVIER, 2006) Marugán, J.; Hufschmidt, D.; Sagawe, G.; Selzer, V.; Bahnemann, D.
Over the last years, many research groups have developed supported TiO2-based materials in order to improve the engineering applications of photocatalytic technologies. However, not many attempts have been made to evaluate the optical behaviour of these materials. This work focuses on the study of the photonic efficiencies of silica-supported TiO2 photocatalysts following the photodegradation of dichloroacetic acid (DCA) as model compound. Catalysts with different types of silica support and titania loadings were tested and their activity was found to be in correlation with the results of the clusters size distribution of the TiO2 nanocrystals. The photonic efficiency of the supported photocatalysts depends extremely on the optical density of the solid suspensions. Influence of the textural properties of the support and the titania loading on the optical density as well as on the photonic efficiency of the materials are discussed. The dependence of the absorption of radiation by the suspension on the catalyst concentration is also analyzed.
Photocatalytic inactivation of dual- and mono-species biofilms by immobilized TiO2
(Elsevier, 2021) Pablos, C.; Govaert, M.; Angarano, V.; Smet, C.; Marugán, J.; Van Impe, J.F.M
Biofilms formed by different bacterial species are likely to play key roles in photocatalytic resistance. This study aims to evaluate the efficacy of a photocatalytic immobilized nanotube system (TiO2-NT) (IS) and suspended nanoparticles (TiO2-NP) (SS) against mono- and dual-species biofilms developed by Gram-negative and Gram-positive strains. Two main factors were corroborated to significantly affect the biofilm resistance during photocatalytic inactivation, i.e., the biofilm-growth conditions and biofilm-forming surfaces. Gram-positive bacteria showed great photosensitivity when forming dual-species biofilms in comparison with the Gram-positive bacteria in single communities. When grown onto TiO2-NT (IS) surfaces for immobilized photocatalytic systems, mono- and dual-species biofilms did not exhibit differences in photocatalytic inactivation according to kinetic constant values (p > 0.05) but led to a reduction of ca. 3–4 log10. However, TiO2-NT (IS) surfaces did affect biofilm colonization as the growth of mono-species biofilms of Gram-negative and Gram-positive bacteria is significantly (p ≤ 0.05) favored compared to co-culturing; although, the photocatalytic inactivation rate did not show initial bacterial concentration dependence. The biofilm growth surface (which depends on the photocatalytic configuration) also favored resistance of mono-species biofilms of Gram-positive bacteria compared to that of Gram-negative in immobilized photocatalytic systems, but opposite behavior was confirmed with suspended TiO2 (p ≤ 0.05). Successful efficacy of immobilized TiO2 for inactivation of mono- and dual-species biofilms was accomplished, making it feasible to transfer this technology into real scenarios in water treatment and food processing.
Reflector design for the optimization of photoactivated processes in tubular reactors for water treatment
(Elsevier, 2023) Martín-Sómer, M.; Moreira, J.; Santos, Carla; Gomes, Ana I.; Moreno-SanSegundo, J.; Vilar, Vítor J.P.; Marugán, J.
Photoactivated advanced oxidation processes have excellent performance in removing recalcitrant pollutants from water. However, the high operating cost associated with the energy consumption of UV lamps is a big drawback. In this work, the design and optimization of the reflector in a tube-in-tube membrane photoreactor were carried out using a ray tracing methodology to maximize the light deployed to the reactor. Simulations were carried out using different lamps/reactor arrangements with 1, 2 and 3-sided flat reflectors and with circular and parabolic geometries. Results showed that direct radiation is maximized when the distance reactorlamps is minimized, increasing optical efficiency. On the other hand, it was observed that for the flat reflectors, the closer the furthest point of the reflector to the center of the reactor, the higher optical efficiency is achieved due to the reduction in the number of bouncing rays in the reflector. In the case of parabolic geometries, some additional considerations are necessary, since not only the distance at which the reflector is placed matters, but also its geometrical focus. The best performance is achieved for those in which the distance from the furthest point of the reflector to the center of the reactor was lower and the lamps placed near the focus of the parabola. For the studied reflector geometries, the calculated optical efficiencies when using anodized aluminum were 46.1%, 56.5%, 60.0%, 41.8%, and 65.9% for reflectors of 1, 2, and 3 sides, cylinder, and parabola, respectively. Model predictions were successfully validated using experimental ferrioxalate actinometry data, confirming the huge potential of this simple simulation methodology for photoreactor design purposes.
Removal of cyanides in wastewater by supported TiO2-based photocatalysts
(ELSEVIER, 2002) Aguado, José; van Grieken, R.; López Muñoz, M.J.; Marugán, J.
Titania supported samples on different types of silica have been prepared through a sol-gel method followed by hydrothermal processing. The photocatalytic activity of the samples was tested for free cyanides photo-oxidation. As compared to commercial TiO2 all the synthesized materials showed not only similar photocatalytic efficiencies but improved recovery properties. The degradation of iron (III) cyanocomplexes was also studied in the absence or presence of titania catalyst. In all cases, a photoinduced CN¿ released from the complex takes place through a homogeneous process. The further oxidation of those cyanides ions to cyanate species is significantly enhanced in the presence of the catalyst in which mesostructured SBA-15 silica is used as support.