Examinando por Autor "VAN GRIEKEN, RAFAEL"

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Assessing the efficacy of novel and conventional disinfectants on Salmonella cross contamination during washing of fresh-cut lettuce and their impact on product shelf life
(ELSEVIER, 2022-06) PABLOS, CRISTINA; ROMERO, AITOR; DE DIEGO, ANA; CORRALES, CARLA; VAN GRIEKEN, RAFAEL; BASCÓN, ISABEL; PÉREZ-RODRÍGUEZ, FERNANDO; MARUGÁN, JAVIER
The effect of the application of different disinfectants on the microbial load and sensory quality of fresh-cut lettuce was evaluated during washing, and after subsequent storage at 4 °C under modified atmosphere packaging (MAP). Different families of potential alternative sanitizers were tested: quaternary ammonium compounds (QACs) as benzalkonium chloride (BZK), and didecyldimethylammonium chloride (DDAC); isothiazolinones (mixture of chloromethylisothiazolinone and methylisothiazolinone, CMIT:MIT 3:1); and, essential oils (carvacrol, CAR). All these disinfectants were effective to inactivate Salmonella (103 CFU/mL) present in wash water. In addition, all tested chemicals could reduce Salmonella on produce to levels >95%, with chlorine and BZK-CAR reaching maximum reductions of 99.0%. These disinfectants also enhanced a reduction in natural microbiota present on the produce. The highest reduction corresponded to free chlorine (50 mg/L) (95.1%), CMIT:MIT (50 mg/L) (Kathon®) (94.5%), and BZK (300 mg/L) (91.3%). However, only free chlorine (50 mg/L), CMIT:MIT (50 mg/L) (Kathon®), and DDAC (100 mg/L) resulted in minimal negative impact on end-product quality during 14-day storage. On the contrary, an adequate sensory quality could be only maintained up to 7 days for produce treated with BZK (300 mg/L).
Critical role of the light spectrum on the simulation of solar photocatalytic reactors
(ELSEVIER, 2019-09-05) VAN GRIEKEN, RAFAEL; CASADO, CINTIA; GARCÍA-GIL, ÁNGELA; MARUGÁN, JAVIER
This work describes the critical role of the matching between the spectral distribution of the incident light and the absorption spectra of the semiconductor material on the accuracy of the simulation of solar photocatalytic reactors. In silico results have been generated by a multiphysics model including the rigorous description of the hydrodynamics, radiation transfer, mass transport and chemical reaction rate, with the particular feature of using a spectral band discretization approach for the resolution of the radiation balance and the estimation of the spectral local volumetric rate of photon absorption. Model predictions with a mechanistic kinetic model have been experimentally validated using a solar reactor based on a tubular reactor coupled to a compound parabolic collector (CPC) under illumination with a solar simulator (xenon lamp) and natural sunlight. Small differences in the spectral distribution of both light sources led to significantly different predictions for the reaction rate, explaining the higher efficiency experimentally achieved with natural sunlight in comparison with the solar simulator for equivalent total UV-A irradiances. The developed model is able to explain the discrepancies between experimental results in solar simulators and under natural sunlight, usually reported in the literature, offering a novel numerical approach for rigorous modelling of photoreactors using light sources with any spectral distribution.
Novel macroporous 3D photocatalytic foams for simultaneous wastewater disinfection and removal of contaminants of emerging concern
(ELSEVIER, 2019-06-15) VAN GRIEKEN, RAFAEL; MARTÍN-SOMER, MIGUEL; MARUGÁN, JAVIER; PABLOS, CRISTINA; DE DIEGO, ANA; ENCINAS, ÁNGEL; MONSALVO, VICTOR M.
A comparative study of the photocatalytic efficiency obtained in water disinfection and the simultaneous removal of micropollutants was carried out by using three different TiO2 photocatalytic materials. The three photocatalysts were immobilized in macroporous reticulated ZrO2 3D foams and their efficiency was compared with that obtained in suspensions for the treatment of synthetic and real wastewater. The results obtained show similar photocatalytic efficiencies for the three photocatalysts used, showing the catalysts WTT-P and AQ1 to be an alternative to the common use of P25 catalyst. The use of supported photocatalysts in the treatment of synthetic water showed lower efficiencies compared to the suspended photocatalysts due to the existence of diffusive limitations caused by the low concentration of the micropollutants. However, these differences were not observed when treating a wastewater treatment effluent. In this case, the non-selective action of the hydroxyl radicals causes the loss of a significant part of the available radicals for the oxidation of non-target compounds present in the water. Consequently, diffusion was not identified as the limiting stage of the removal rate, but the availability of hydroxyl radicals in the reaction medium, which allows the 3D foams to be as effective as the processes in suspension.
Wavelength dependence of the efficiency of photocatalytic processes for water treatment
(ELSEVIER, 2018) VAN GRIEKEN, RAFAEL; PABLOS, CRISTINA; MARUGÁN, JAVIER; VEGA, BEATRIZ; MARTÍN-SOMER, MIGUEL
The main objective of this work is to present a novel approach to evaluate quantitatively the action spectra and energy efficiency for chemical oxidation and bacterial inactivation of photocatalytic processes using monochromatic LED sources. Two different catalysts with different absorption spectra (TiO2 and iron citrate complex) were used. In all cases, it was confirmed a direct relationship between the absorption spectrum of the catalyst and the spectral dependence of the photonic efficiency. The best alternative for TiO2 processes in terms of energy consumption when using artificial lighting is the use of 365 nm. In contrast, for iron complexes it seems more economically feasible the use of longer wavelengths close to the visible range, because the lower absorption of the complex is counterbalanced by the higher energy efficiency of the LED devices. This can be obviously extrapolated to the use of sunlight, where the use of iron-based photocatalytic processes can harvest a higher fraction of the available light. Predictions of the process efficiency under solar irradiation based on the action spectra determined with LED at laboratory scale have been successfully validated by experimental data. The methodology proposed in this work could be easily extrapolated to other wavelength ranges required by novel catalysts or efficient short wavelength monochromatic LED sources available in the future.