Examinando por Autor "Alfano, Orlando M."

Mostrando 1 - 5 de 5

Intrinsic kinetic modelling with explicit radiation absorption effects of the photocatalytic oxidation of cyanide with TiO2 and silica-supported TiO2 suspensions
(ELSEVIER, 2008) Marugan, Javier; van Grieken, Rafael; Cassano, Alberto E.; Alfano, Orlando M.
This study is focused on the kinetic modeling of the photocatalytic oxidation of cyanide in slurry reactors. The developed model is based on an accepted reaction mechanism and takes into account explicitly the differences in the local volumetric rate of photon absorption (LVRPA) produced by the unavoidable radiation profiles existing in the photoreactor. The model and its correspondent procedures for the evaluation of the LVRPA distribution and the estimation of the kinetic parameters have been successfully validated with both powder TiO2 and TiO2/SiO2 photocatalysts with improved recovery properties. In both cases, the model reproduces the influence of the catalyst loading, the initial cyanide concentration, and the inlet radiation flux on the reaction rate, with errors below 5 %. The kinetic parameters estimated for the model are independent of the irradiation form, as well as the reactor size and its geometrical configuration, providing the necessary information for scaling-up and designing commercial scale photoreactors.
Kinetic modelling of Escherichia coli inactivation in a photocatalytic wall reactor
(Elsevier, 2014) Marugán, Javier; Grieken, Rafael van; Pablos, Cristina; Satuf, M. Lucila; Cassano, Alberto E.; Alfano, Orlando M.
A kinetic model of the photocatalytic inactivation of Escherichia coli in an annular wall reactor is presented. The model is based on a reaction scheme that involves a series of events in which bacteria are progressively damaged and eventually led to cell lysis. The model explicitly takes into account radiation absorption effects. Photocatalytic inactivation experiments were carried out in a photoreactor operated in a closed recirculating circuit with a reservoir tank and irradiated with a 6W black light lamp situated in the axis of the reactor. Immobilization of TiO2 Aeroxide P25 has been carried out by the dip-coating procedure onto the inner-tube wall of the annular reactor. Experimental results for different TiO2 layer thicknesses were used to estimate the kinetic parameters of the model. Good agreement between model predictions and inactivation experiments was achieved in the whole range of TiO2 thicknesses studied.
Quantum efficiency of cyanide photooxidation with TiO2/SiO2 catalysts: Multivariate analysis by experimental design
(ELSEVIER, 2007) Marugán, Javier; van Grieken, Rafael; Cassano, Alberto E.; Alfano, Orlando M.
Despite the large amount of work dealing with supported photocatalysts used to overcome the difficulties associated with the recovery of powdered titania after the photocatalytic treatments, few attempts have been made to calculate the quantum efficiency () of these materials. In this work the quantum efficiency for the photooxidation of cyanide with TiO2 and TiO2/SiO2 has been experimentally calculated using an approach based on the resolution of the radiative transfer equation inside the photoreactor. Due to the low absorption coefficient of the silica-supported material, a 2-dimensional 2-directional reactor model has been developed to describe the photon transport. The dependence of on the incident radiation flux, the catalysts concentration and the cyanide concentration has been investigated. With both material suspensions, higher quantum efficiencies have been observed when lower radiation fluxes and higher cyanide concentrations are used. However different trends in the quantum efficiencies are observed when increasing the catalyst concentration, leading to higher values when using powdered TiO2 and lower values for TiO2/SiO2 suspensions.
Rigorous kinetic modelling with explicit radiation absorption effects of the photocatalytic inactivation of bacteria in water using suspended titanium dioxide
(ELSEVIER, 2011) Marugán, Javier; van Grieken, Rafael; Pablos, Cristina; Satuf, M. Lucila; Cassano, Alberto E.; Alfano, Orlando M.
This study is focused on the kinetic modelling of the photocatalytic inactivation of bacteria with suspended TiO2. A rigorous model based on a proposed reaction mechanism and accounting explicitly for the rate of photon absorption has been developed. The application of the general kinetic expression to limiting cases suggests that the interaction bacteria-catalyst can be considered to be weak. In contrast, a complex dependence on the radiation absorption rate must be taken into account, as very different radiation conditions may coexist inside the photoreactor, with high absorption rates in the region near to the radiation entrance window and much lower values on the opposite side of the photoreactor. The model has been successfully validated by experimental data, being able to reproduce the evolution of the concentration of viable bacteria in a wide range of values of TiO2 concentration, irradiation power and initial concentration of bacteria with a normalized root mean square logarithmic error of 5.3 %. The values of the kinetic parameters are independent of the specific reactor setup or the operating conditions and therefore, the model can be used in a predictive way for photoreactor design and scaling-up, as well as for the optimization of other reactor configurations.
Scaling-up slurry reactors for the photocatalytic oxidation of CYANIDE with TiO2 and SILICA-SUPPORTED TiO2 suspensions
(ELSEVIER, 2009) Marugan, Javier; van Grieken, Rafael; Cassano, Alberto E.; Alfano, Orlando M.
A scaling-up methodology for the design of large scale slurry reactors for the photocatalytic oxidation of cyanide is proposed. The only experimental information required to be determined at laboratory scale is the intrinsic kinetics that describes the explicit dependence of the reaction rate with the local volumetric rate of photon absorption (LVRPA). Based on the kinetic model and the information about the geometry, irradiation source and the cyanide and catalyst concentrations as operation conditions, the performance of a larger scale reactor has been simulated following a predictive procedure with no adjustable parameters. The validation of the method has been carried out in a bench-scale reactor with ten times higher irradiated volume and a different geometry and irradiation source, in order to ensure that the conclusions about the applicability of the scaling-up model are independent of these parameters. The proposed scaling-up methodology and their correspondent procedures for the evaluation of the LVRPA distribution on the photoreactors has been successfully validated both with commercial TiO2 and a silica-supported TiO2 synthesized in our laboratory. The normalized root mean square error in the verification of the conversions predicted by the model for the larger scale reactor when compared with the experimental data are 7.7% and 6.2 % for TiO2 and TiO2/SiO2, respectively.