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Different visible light responses of commercial TiO2photocatalysts are assessed for theirapplication in air decontamination. To do that the modified TiO2catalysts were immobi-lized on borosilicate glass plates according to a dip coating method. Then, the photocatalyticperformance of these plates was evaluated in a continuous gas flat plate photoreactor irra-diated with visible light lamps using two representative air pollutants: nitrogen oxide andacetaldehyde. Working under visible light, the modified TiO2catalysts were compared bymeans of efficiency parameters: the true quantum efficiency, which relates the moles ofdegraded pollutant with the moles of the absorbed photons, and the apparent photonicefficiency, which relates the moles of degraded pollutant with the moles of incident pho-tons. Also, the photocatalytic pollutants degradation by immobilized modified TiO2could berelated with their optical properties, finding a clear correlation between them. These resultsare useful to decide which TiO2will be more efficient for a full scale air decontaminationprocess under visible light illumination. Fil: Ballari, Maria de Los Milagros. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Carballada, J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Minen, Romina Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Salvadores, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Brouwers, H. J. H.. Eindhoven University of Technology; Países Bajos Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

The disinfection efficiencies of a commercial mixture of peracetic acid against Escherichia coli were studied in laboratory scale experiments. The joint and separate action of two disinfectant agents, hydrogen peroxide and peracetic acid, were evaluated in order to observe synergistic effects. A kinetic model for each component of the mixture and for the commercial mixture was proposed. Through simple mathematical equations, the model describes different stages of attack by disinfectants during the inactivation process. Based on the experiments and the kinetic parameters obtained, it could be established that the efficiency of hydrogen peroxide was much lower than that of peracetic acid alone. However, the contribution of hydrogen peroxide was very important in the commercial mixture. It should be noted that this improvement occurred only after peracetic acid had initiated the attack on the cell. This synergistic effect was successfully explained by the proposed scheme and was verified by experimental results. Besides providing a clearer mechanistic understanding of water disinfection, such models may improve our ability to design reactors. Fil: Flores, Marina Judith. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Brandi, Rodolfo Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Labas, Marisol Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

Optical properties of iron pillared clays (Fe-PILCs) were determined by using spectrophotometer measurements coupled with the solution of the radiative transfer equation (RTE). The specific absorption and scattering coefficients, as well as the phase function for scattering, were obtained as a function of the wavelength in the range from 300 to 500 nm. Optical properties of the Fe-PILCs are greatly affected by their iron contents which are ascribed to changes in their textural properties and are significantly different from those of two other iron containing materials, goethite and zerovalent iron. To show an application of the optical properties, the quantum efficiency of the heterogeneous photo-Fenton process with a Fe-PILC was determined. The results indicate that Fe-PILCs could be used as catalysts in large-scale photoreactors whose dimensions could be adjusted in a wide range according to the catalyst load and iron content to be used. Fil: de Leon, María A.. Universidad de la Republica. Facultad de Quimica; Uruguay Fil: Sergio, Marta. Universidad de la Republica. Facultad de Quimica; Uruguay Fil: Bussi, Juan. Universidad de la Republica. Facultad de Quimica; Uruguay Fil: Ortiz de la Plata, Guadalupe Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina

The aim of this work is to study the degradation kinetics of the endocrine disruptor Benzyl Butyl Phthalate using Ozone and UV radiation. The model comprises four parallel sub-systems that are identified and isolated: (1) direct photolysis, (2) direct ozonation in the absence of hydroxyl radicals, (3) complete ozonation (direct + indirect oxidation) and (4) ozone + UV. To determine the nature of ozone attacks and the influence of ?OH radicals on O3 activity, two sets of experiments were performed: (i) Conventional ozonation and (ii) the same ozonation experiments in the presence of tert-butanol as radical scavenger, where only the reactions involving molecular ozone are present. The explored variables were: (i) Ozone concentration, (ii) Incident radiation rate at the reactor windows, (iii) reaction pH and (iv) the presence of radical scavengers. Major intermediates of BBP degradation were identified. Degradation kinetics was correctly modeled by a pseudo-second order kinetic model based on the sum of all the effects occurring during the treatment. The corresponding kinetic constants were obtained and the relative contributions of each of the considered subsystems were evaluated. Fil: Lovato, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Gilliard, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Martin, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina

A kinetic model for the simultaneous degradation of dichloroacetic acid (DCAA) and formic acid (FA) has been developed. The oxidation is produced by the combination of hydrogen peroxide (HP) and UV (253.7 nm) radiation. A set of four equations, three differentials and one algebraic, represents the time evolution of the concentration of DCAA, FA, HP and hydrochloric acid (HCl), a measurable by-product. The model is based on a complete reaction mechanism, which comprises hydrogen peroxide photolysis and decomposition of dichloroacetic and formic acids. It takes into account the effect of non-uniform distribution of the local rate of absorbed photons. The mathematical model renders simulation results that agree with the experimental data. It was also shown that FA decays much faster than DCAA. Fil: Mariani, Melisa Lourdes. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET- Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina; Fil: Brandi, Rodolfo Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET- Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina; Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET- Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina; Fil: Zalazar, Cristina Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET- Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina

The H2O2/UVC process was applied to the photodegradation of a commercial formulation of glyphosate in water. Two organisms (Vibrio fischeri bacteria and Rhinella arenarum tadpoles) were used to investigate the toxicity of glyphosate in samples M1, M2, and M3 following different photodegradation reaction times (120, 240 and 360 min, respectively) that had differing amounts of residual H2O2. Subsamples of M1, M2, and M3 were then used to create samples M1,E, M2,E and M3,E in which the H2O2 had been removed. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were measured in tadpoles to determine possible sub-lethal effects. In V. fischeri, M1,E, which was collected early in the photodegradation process, caused 52% inhibition, while M3,E, which was collected at the end of the photodegradation process, caused only 17% inhibition. Survival of tadpoles was 100% in samples M2, M3, and in M1,E, M2,E and M3,E. The lowest percentages of enzymatic inhibition were observed in samples without removal of H2O2: 13.96% (AChE) and 16% (BChE) for M2, and 24.12% (AChE) and 13.83% (BChE) for M3. These results show the efficiency of the H2O2/UVC process in reducing the toxicity of water or wastewater polluted by commercial formulations of glyphosate. According to the ecotoxicity assays, the conditions corresponding to M2 (11 ± 1 mg a.e. L−1 glyphosate and 11 ± 1 mg L−1 H2O2) could be used as a final point for glyphosate treatment with the H2O2/UV process. Fil: Junges, Celina Maria. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe; Argentina Fil: Vidal, Eduardo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina Fil: Attademo, Andres Maximiliano. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe; Argentina Fil: Mariani, Melisa Lourdes. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina Fil: Cardell, Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina Fil: Negro, Antonio Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina. Universidad Nacional del Litoral. Facultad de Ingenieria y Ciencias Hidricas. Departamento de Medio Ambiente; Argentina Fil: Peltzer, Paola. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe; Argentina Fil: Lajmanovich, Rafael Carlos. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe; Argentina Fil: Zalazar, Cristina Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina. Universidad Nacional del Litoral. Facultad de Ingenieria y Ciencias Hidricas. Departamento de Medio Ambiente; Argentina

A detailed reaction–reactor model of the kinetics of dichloroacetic acid (DCA) degradation employing ozone with UVC radiation was developed. The description differentiates the existence of illuminated and dark sections of the reacting system, as well as shows the application of the differential concept of chemically active species radiation absorption coefficients and the ones corresponding to other components that only participate in the characterization of the total existing radiation field. A distinction is made between the mass balances for ozone (operating in a well-stirred, recirculating, continuous flow reactor) and all other intervening species (operating in a well mixed, recirculating batch reactor). Additionally, the conceptualization of the requirement of a fully irradiated photochemical reactor is applied in order to confer meaningfulness to the obtained kinetic parameters. The complete sequence presented here includes three parallel reactions: (i) direct photolysis, (ii) direct ozonation and (iii) ozonation plus UVC radiation. This study attempts to reach one single 31 steps sequence that, by suitable cancellation of the reaction paths that specifically do not take part in each of the corresponding processes, reproduces the kinetics of direct photolysis or direct ozonation without UV radiation. Three sets of ordinary differential equations resulting from the mass balances of each one of the three parallel reactions are reported. Upon estimation of the missing kinetic constants for DCA, simulation results always show good agreement with experimental data. Through a parametric sensitivity analysis, it has been shown that without loss of accuracy, the model can be safely reduced to just 23 steps.

This glossary of terms covers phenomena considered under the very wide terms photocatalysis and radiation catalysis. A clear distinction is made between phenomena related to either photochemistry and photocatalysis or radiation chemistry and radiation catalysis. The term “radiation” is used here as embracing electromagnetic radiation of all wavelengths, but in general excluding fast-moving particles. Consistent definitions are given of terms in the areas mentioned above, as well as definitions of the most important parameters used for the quantitative description of the phenomena. Terms related to the up-scaling of photocatalytic processes for industrial applications have been included. This Glossary should be used together with the Glossary of terms used in photochemistry, 3rd edition, IUPAC Recommendations 2006: (doi:10.1351/pac200779030293) as well as with the IUPAC Compendium of Chemical Terminology, 2nd ed. (the “Gold Book”, 2006– doi:10.1351/goldbook) because many terms used in photocatalysis are defined in these documents.

In the present work the existente of mass transfer limitations in slurry, photocatalytic reactors is studied. Experimental validation is made in a flat plate reactor that is part of a recycling system. The reactor is described with a mathematical model previously developed [Ballari et al., 2008a. Chemical Engineering Journal 136, 50], considering a transient, two-dimensional mass balance (TDM). The complete reactor model was developed to show the existence of these effects, which result from the occurrence of concentration gradients in reaction space. They develop when these reactors are operated under some operating conditions whose effects should be always analyzed before assuming the validity of existence of perfect mixing in reaction space. Dichloroacetic acid (DCA) was the adopted model compound. To solve TDM, a kinetic expression for DCA acid was determined before under well mixed conditions [Ballari et al., 2009. Industrial and Engineering Chemistry Research 48(4), 1847]. The studied variables are flow rate, catalyst loading, and irradiation rates. The experimental data agree quite well when they are interpreted in terms of the two-dimensional model (TDM) regardless of the operating mode. The perfect mixing model (PMM), normally employed to describe this and other types of slurry photoreactors, does not have the same level of universal application; i.e. it is restricted to perfect mixing, but in many cases far simpler to use. However, it can be concluded that when the photocatalytic reaction is not fast, employing catalyst loadings below 1gL–1, irradiation rates at the reactor wall below 1x10x-6 Einstein cm-2 s-1 and good mixing operation (Re41700) it will be always safe to assume that mass transport limitations in the bulk of the fluid are non existent. In a typical batch reactor the above flow conditions are equivalent to very intense mixing. If the catalyst concentration is in creased, the mixing conditions should be improved in the same proportion. Within limits, higher solid loadings can be compensated with lower irradiation rates[Ballarietal.,2008a. Chemical Engineering Journal 136, 50]. In addition, with the validated model, additional simulations are shown, operating the reactor under different virtual reactor thicknesses to widen amplitude of the reached conclusions. These findings Hill be useful in kinetic studies to prevent incursion in certain ranges of experimental conditions that could lead to erroneous interpretation of the obtained kinetic data. Fil: Ballari, Maria de Los Milagros. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina. Universidad Nacional del Litoral; Argentina Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina. Universidad Nacional del Litoral; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina. Universidad Nacional del Litoral; Argentina

A study has been conducted on the decomposition of 2-chlorophenol (2-CP) applying a heterogeneous Fenton reaction using goethite as catalyst at pH 3. The research was aimed at obtaining a workable kinetic expression apt for developing a kinetic model for scaling up purposes. Several aspects of the reaction have been described in the available literature but, for the moment, without a reasonable representation of the entire reaction behavior. In order to provide a more comprehensive and probable explanation of the whole observed performance, a set of experiments was carried out varying systematically all the significant variables. The proposal considers that the reaction is essentially a combination of four heterogeneous processes associated with one typical homogeneous Fenton reaction. Three of the surface reactions explain a very small iron leaching to the medium by a proton induced solubilization, a reductive dissolution reaction and a non-reductive iron release produced by detected 2-CP chemical decomposition byproducts, particularly, chlorohydroquinone (ClHQ) and oxalic acid (OxA). Iron concentration in the solution may be further increased in the final stages of the reaction after most of the 2-CP has been degraded, by the appearance of OxA that takes part in a third surface reaction. The fourth heterogeneous reaction rationalizes the unusual hydrogen peroxide consumption at high catalyst loadings. During the homogeneous reaction, the presence of ClHQ and ClBQ produces a homogeneous autocatalytic beneficial enhancement of the Fe3+ → Fe2+ transformation. Consequently, the existence of phenolic derivatives either in the mixture or as reaction byproducts produces a beneficial enhancement of the reaction rate. Very low iron leaching is required to produce the onset of the homogeneous Fenton reaction, which was shown to be strongly dependent upon the reaction temperature. All the experimental findings were satisfactorily described by a set of 19-step feasible reaction scheme. The process could be useful for the treatment of wastewaters containing pollutants with phenolic derivatives, as long as iron leaching remains within tolerable limits.

The kinetics of the degradation of 2-chlorophenol (2-CP) employing both the heterogeneous Fenton and photo-Fenton reactions using goethite as the solid catalyst is studied. The photoreactor was irradiated with a 350–400 nm wavelength light. The kinetics is based on 19 steps of a combined heterogeneous–homogeneous mechanism derived for the thermal Fenton reaction [see companion article by the authors: Ortiz de la Plata et al. (2009)] [1] . For the photo-Fenton alternative, two more steps are needed. Some of the specific kinetic constants of the reaction scheme are approximately known. However, for the heterogeneous “thermal” Fenton reaction, three new unknown constants were required and were attained from experimental data obtained in this and the previous work. The parameters were (i) the reaction of the HO radical with 2-CP, (ii) the proton induced iron dissolution and (iii) the reductive induced iron dissolution [1] . In the case of the heterogeneous photo-Fenton reaction steps, the radiation field in the reacting system was described by solving the complete radiative transfer equation inside the reactor. With this purpose, the knowledge of the needed goethite optical properties were previously characterized [2] . Combining the dark and the irradiated experiments 21 kinetically consistent parameters were achieved for the proposal of a feasible mechanism. They are valid for both systems; making the two primary quantum yields of the photoreaction equal to zero, the “dark” Fenton reaction performance is properly described by the remaining 19 specific rate constants. These results are independent of the used experimental apparatus and can be safely used for scaling-up purposes within the range of the explored variables.

The photocatalytic degradation of radiation absorbing and nonabsorbing pollutants in slurry reactors is analyzed in terms of two performance parameters: the observed photonic efficiency (OPE) and t...

A comprehensive kinetic model for the photooxidation of oxalic acid (C 2 O 4 H 4 ) in a fluidized bed (FB) of a TiO 2 /quartz sand composite, in a UV-fully illuminated photoreactor, was developed and correlated with experimental results. A proper solution for the mass balance of the reacting system was achieved by combining the complete radiation field profile and the most recent and updated pathway for the adsorption and photodecomposition of oxalic acid onto TiO 2 ( Mendive et al., 2007 ), which was employed to determine the kinetic expression and model parameters.

In a broad sense, photochemical reactions proceed through pathways involving several reaction steps. The initiation step is the absorption of energy both by the reactant or sensitizer molecules and in some cases, by the catalyst, leading to intermediate products that ultimately give rise to stable end products. Preferably, the reaction rate expression is derived from a proposed mechanism together with sound simplifying assumptions; otherwise, it may be adopted on an empirical basis. Under a kinetic control regime, the rate expression thus obtained depends on the local rate of photon absorption according to a power law whose exponent very often ranges from one half to unity. The kinetic expression should be valid at every point of the reactor volume. However, due to radiation attenuation in an absorbing and/or scattering medium, the value of the photon absorption rate is always a function of the spatial position. Therefore, the overall photochemical reaction rate will not be uniform throughout the entire reaction zone, and the distinction between local and volume average photochemical reaction rates becomes mandatory. Experimental values of reaction rates obtained from concentration measurements performed in well-mixed reaction cells are, necessarily, average values. Consequently, for validation purposes, experimental results from these cells must be compared with volume averages of the mechanistically or empirically derived local reaction rate expressions. In this work it is shown that unless the rate is first order with respect to the photon absorption rate or the attenuation in the absorbing and/or scattering medium is kept very low, when the averaging operation is not performed, significant errors may be expected. Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Irazoqui, Horacio Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

This study is focused on the kineticmodeling of the photocatalytic oxidation of cyanide in slurry reactors. The developed model is based on an accepted reaction mechanism and explicitly takes into account 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. Fil: Marugan, Javier. Universidad Rey Juan Carlos; España Fil: Van Grieken, Rafael. Universidad Rey Juan Carlos; España Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

A kinetic study of the photocatalytic degradation of 4-chlorophenol employing titanium dioxide is presented. Experiments were carried out in a cylindrical slurry reactor irradiated by UV lamps. The aromatic reaction intermediates were identified and quantified. Intrinsic expressions to represent the kinetics of 4-chlorophenol and the main intermediates, 4-chlorocatechol and hydroquinone, were derived from a proposed reaction scheme. These expressions include explicitly the effect of photon absorption on the reaction rate. The modeling of the radiation field in the reactor was accomplished by solving the radiative transfer equation with the discrete ordinate method. Experimental runs were performed by varying the catalyst concentration, the incident radiation, and the reactor length. The parameters of the kinetic model were estimated from the experiments by applying a non-linear regression procedure. Good agreement was obtained between model predictions and experimental data, with a root mean square error of 14.4%.

Optical properties of solid catalysts needed for a rigorous modeling of heterogeneous photo-Fenton reaction kinetics and the ultimate reactor design have not been studied so far. Without these data, quantitative information concerning the influence of the radiation field in the process performance is almost impossible. These reactions are still under the first stages of their studies, and most of the effort has been aimed at elucidate yields, tentative mechanisms, the optimum operating pH and ways to reduce iron ions leaching to the aqueous solution. This work reports the values of above-mentioned parameters precisely calculated, resorting to specially designed spectrophotometer measurements coupled with the solution of the radiative transfer equation (RTE). Goethite, a natural occurring ferric oxide, was studied to obtain the values of the radiation linear volumetric absorption and scattering coefficients, as well as the phase function for scattering, some of them as a function of mass composition, and all of them as a function of the wavelength range between 310 and 500 nm. The results indicate that, in addition to its demonstrated ability to degrade effectively many contaminants, its optical properties exhibit very low absorption and scattering properties. This outcome improves its potentiality for applications in large-scale reactors, because the resulting useful optical path length will be significantly large. Specifically, these results are compared with a typical photocatalytic substance, such as titanium dioxide to remark the differences. Fil: Ortiz de la Plata, Guadalupe Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

This work is a continuation of a previous study concerning the problem of mass transfer limitations in slurry, photocatalytic reactors employing pure, titanium dioxide suspensions. With simulation experiments applied to an existing isothermal reactor, the mineralization reaction of dichloroacetic acid was used as a test reaction because introducing some corrections in the model of a published work, and resorting to the original experimental data, an intrinsic reaction kinetics was available. In the first part, only irreducible radiation field non-uniformities and the existence, under some operating conditions, of strong, mass concentration gradients in the bulk were explored. It was found that the last might be significant unless very good mixing conditions prevail. In this second part, the study is concentrated on external and internal catalytic particles (or agglomerates) transport limitations. In this case, resorting to the definition of a specifically defined photocatalytic effectiveness factor, the coupled effects of concentration gradients and light penetration impediments can be analyzed separately. The mathematical description of the catalytic particle (or agglomerate) performance is made employing rigorous, radiation and mass transfer models derived from fundamental principles. The main explored variables were (i) irradiation rates, particularly considering the influence of the wavelength distribution of the employed radiation, (ii) size of the catalytic particles and their eventual agglomerations, (iii) virtual changes in the reaction rate, to include the possibility of faster reactions, (iv) catalyst loadings and (v) porosity of the catalyst agglomeration. Only for very large particles, not usually employed with unsupported titanium dioxide, interfacial external mass transfer limitations in the boundary layer surrounding the catalytic particle may be significant. Inside the catalytic particle or the porous agglomerate, the most important restriction is the light penetration that can be observed even in particle sizes (or agglomerates) below 1 μm.

The inactivation reaction of Escherichia coli bacteria employing hydrogen peroxide at 20 ºC and pH = 7 was studied in a well-mixed batch reactor. The proposed objective, as far as the extent of inactivation is concerned, was obtained for H2O2 concentrations above 100 ppm (1 ppm = 2.94×10-5 mmol cm-3) but, compared with other disinfection technologies, for too long reaction times. Below 40 ppm of the oxidant concentration inactivation was practically ineffective. Results were analyzed employing Modified forms of the Series-Event and Multitarget mechanistic models. At concentrations above 100 ppm the induction time in the semi-logarithmic plot of bacteria concentration versus time was reduced. With both modified models it was found that the reaction order with respect to the hydrogen peroxide concentration was different than one. Both mathematical descriptions provide a good representation of the experimental results in an ample range of the disinfectant concentrations and confirm a methodology that renders the starting point of a reaction kinetic expression useful for further studies regarding the optimization of the operating conditions (pH and temperature, for example), including also combination with other advanced oxidation technologies. An interpretation of the data in terms of a Weibull-like model [1] is also included. Fil: Labas, Marisol Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Zalazar, Cristina Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Brandi, Rodolfo Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Instituto de Desarrollo Tecnologico para la Industria Quimica. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnologico para la Industria Quimica; Argentina

This chapter describe the methodology for the full predictive simulation of photocatalytic reactors with engineering and design purposes. A rigorous approach based on the resolution of the conservation equations of momentum, mass and radiant energy of the system will be used, emphasizing the similarities and differences with conventional chemical reactors. One of the key steps for making feasible the predictive simulation of reactors with different sizes, geometries and light sources is the availability of an intrinsic kinetic model of the process based on a reaction mechanism that takes into account the radiation absorption step in an explicit way. The procedure for the determination of this type of kinetic model based on experimental data at laboratory scale requires knowledge of the optical properties of the photocatalytic material, requisite for the resolution of the radiative transfer equation that would provide the rigorous description of the radiation field in the reactor. A case study of the application of this methodology to the photocatalytic oxidation of cyanide with TiO2/SiO2 materials is included, describing in detail each step of the procedure.

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 (h) 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 two-dimensional two-directional reactor model has been developed to describe the photon transport. The dependence of h 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. Fil: Marugan, Javier. Universidad Rey Juan Carlos; España Fil: Van Grieken, Rafael. Universidad Rey Juan Carlos; España Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

A kinetic expression to represent the photocatalytic degradation of 4-chlorophenol (4-CP) has been derived in a small, well-stirred, slurry reactor. Based on a plausible reaction sequence, the obtained mathematical representation describes with good accuracy the decomposition of 4-CP as well as the evolution of the most important reaction intermediates. This information is used to actionate a very different reactor in size, shape and operating conditions. The adopted approach consists in the precise modeling of the laboratory reactor to estimate intrinsic kinetic parameters. Afterward, the reaction kinetics obtained in the small reactor is used to model a bench scale reactor, without employing any adjustable parameters. Simulation results are in good agreement with the experimental data obtained in the larger reactor. This approach points to the development of a full scale-up procedure employing exclusively laboratory reactor information.

The performance of photocatalytic reactors is largely conditioned by their configuration. In particular, photocatalytic wall reactors are affected by configuration-linked factors such as diffusive resistances, reactor radiation incidence and absorption efficiencies, and by the amount of photocatalytic surface area that is effectively irradiated. In this paper, the effect of different configurations and design variables on the performance of annular photocatalytic reactors was analyzed.With this purpose, a complete reactor model was developed and solved, taking into account singleand multi-annular configurations, different reactor dimensions, and three flow patterns. The model was successfully validated against experimental results for the photocatalytic oxidation of perchloroethylene (PCE) in a multi-annular reactor. From the simulation results, it was possible to conclude that the unfavorable effect of the diffusive resistances on the reactor performance could be reduced by constructing photocatalytic annular wall reactors of small annular width and large photocatalytic surface area. Besides, the multi-annular configuration is more effective in using the radiative energy fed into the reactor than the single-annulus reactor configuration. According to the results obtained for PCE photocatalytic degradation, among all the studied reactor configurations the most efficient one is that with its annuli interconnected in a series pattern. Fil: Imoberdorf, Gustavo Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Irazoqui, Horacio Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

In a previous work it has been shown that the combination of H 2 O 2 and low wavelength UV radiation is a suitable process for degrading dichloroacetic acid (DCA). The final result provided a validated and complete reaction scheme. That proposal included two possible ways for the hydroxyl radical to react with DCA [Zalazar, C., Labas, M., Brandi, R., Cassano, A., 2007. Dichloroacetic acid degradation employing hydrogen peroxide and UV radiation. Chemosphere 66, 808–815]. This work was directed to a single objective: to derive, from the previous reaction sequence, a mathematical model able to represent the kinetics of DCA oxidation and validate its predictive quality with experiments. This representation of the reaction must include all the required variables for an ulterior reactor design and scale-up and, consequently, the kinetic model parameters must be independent of the shape, size and configuration of the laboratory reactor. Working with a complete set of experimental runs that included all the involved variables, the unknown kinetics parameters of the DCA degradation were obtained by comparing predicted concentrations by the model (represented by a set of two ordinary differential equations and two algebraic equations coupled with a mass and a radiation balance inside the reactor) with the experimental values, employing a multi-parameter non-linear regression analysis. Experimental values confirmed the validity of the proposed mechanism. Additionally, an optimal concentration ratio of hydrogen peroxide with respect to DCA was obtained ( r = C H 2 O 2 / C DCA ≈ 8 ) . The intermediate results of the numerical solution of the complete system of differential and algebraic equations representing the proposed complete reaction mechanism were useful to find simplified, analytical expressions for the reaction rates of DCA and H 2 O 2 . The obtained rates resulting from these simplifications were compared with those of the complete system showing a very satisfactory concordance. This outcome is, at the same time, a clear indication of the significant influence of the HO 2 ⋅ radical in the reaction evolution.

Radiative energy efficiencies of a multi-annular photocatalytic reactor were evaluated and analysed. The total quantum efficiency, defined as the ratio of the number of molecules of the pollutant reacted to the number of photons emitted by the lamp, is expressed as the product of three factors: (i) the reactor radiation incidence efficiency, (ii) the catalyst radiation absorption efficiency, and (iii) the overall reaction quantum efficiency. By means of a detailed mathematical model, the numerical values of each one were 83, 92, and 0–2.5%, respectively. The dependence of the overall reaction quantum efficiency upon operating variables was also studied. Fil: Imoberdorf, Gustavo Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Irazoqui, Horacio Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

A multi-annular photocatalytic reactor was designed, that shows good effectiveness for perchloroethylene (PCE) removal from contaminated air streams. In a previous work, a rigorous physical and mathematical model of the photocatalytic reactor was developed and experimentally verified. In this work, this mathematical model was used to study the radiative energy efficiency of the multi-annular photoreactor. The total quantum efficiency is defined as the ratio of the number of molecules of PCE reacted to the number of photons emitted by the lamp, and it is expressed as the product of the following factors: the reactor radiation incidence efficiency, the catalyst radiation absorption efficiency, and the overall reaction quantum efficiency. For the employed reactor, the numerical values of each one were 83%, 92%, and

The degradation reaction of dichloroacetic acid employing H(2)O(2) and UVC radiation (253.7nm) has been studied in a well mixed reactor operating inside a recycling system. It has been shown that in an aqueous solution no stable reaction intermediates are formed and, at every time during the reaction, two mols of hydrochloric acid are formed for every mol of dichloroacetic acid that is decomposed and, in the same way, there is a paired agreement between the calculated TOC concentration corresponding to the unaltered dichloroacetic acid and the experimental values measured in the solution. On this basis and classical references from the scientific literature for the H(2)O(2) photolysis, a complete reaction scheme, apt for reaction kinetics mathematical modeling and ulterior scale-up is proposed.

A study of the quantum efficiency of the photocatalytic degradation of 4-chlorophenol (4-CP) in a TiO2 slurry reactor is presented. Also, in order to assess the final conversion of the pollutant into CO2, the efficiency of the mineralization process is defined and evaluated. To calculate these efficiencies, the radiation absorbed by the heterogeneous reacting system needs to be determined. A one-dimensional, one-directional radiation field model is proposed to compute the photon absorption inside the slurry photocatalytic reactor. Degradation rates and quantum efficiencies are analyzed considering the influence of three operating variables: pH, catalyst loading, and irradiation intensity. Important dependencies on these variables were found. The best efficiencies were obtained in acidic conditions, at the highest employed catalyst concentration (1.0 × 10-3 g cm-3) and at the lowest level of irradiation.

Microbiologically contaminated water, in this case artificially infected with Escherichia coli was treated with low wavelength (253.7 nm) radiation in a laboratory reactor where all the significant operating variables were carefully measured and controlled. A modification of the series-event model was used to interpret the experimental data which were collected employing four different levels of the incident radiation arriving at the reactor. The developed model is based on a rather complex dependence with respect to the E. coli concentration and to the radiation that is effectively absorbed by the bacteria which was precisely quantified. The mathematical description of the kinetics has three parameters: (i) the threshold limit of bacteria damage ( n = 2), (ii) the kinetic constant [ k = 9.03 ± 0.36 s −1 (cm 3 W −1 ) m ] and (iii) the reaction order with respect to the bacteria photonic absorption rate ( m = 0.205 ± 0.015). About 99.99% plus inactivation was reached in all cases for rather short effective contact times and predictions from the model agree very well with experimental data in the whole range of investigated variables.

The photochemical efficiency of a fluidized bed (FB) of quartz sand coated with TiO2 by plasma-CVD, was investigated using a fully illuminated, parallel planar photoreactor. The local volumetric rate of photon absorption (LVRPA) of the devicewas obtained by the combined use of experimental measurements and computer modeling of the radiation field. Because of the anisotropy of the FB in the vertical direction, due to particle segregation, and the strong absorption of radiation of the photocatalyst particles across the photoreactor, a two-dimensional modeling (2D) was developed. To accomplish these goals, the relevant specific volumetric optical parameters (namely, the spectral absorption and scattering coefficient) of FBs of the TiO2-coated quartz catalytic composite were used. To take into account said vertical anisotropy of the fluidized bed, a functional dependency between the spectral optical coefficients and bed height was derived in the present work, by assuming a completely segregated FB, and experimentally validated through transmittance measurements. Finally, the evaluation of the photochemical efficiency of the FB in the decomposition of oxalic acid, a well-known model reactant, revealed that this type of devices might outperform the conventional slurry systems, as well as dispense of downstream separation steps Fil: Pozzo, Roberto Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Brandi, Rodolfo Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Giombi, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Baltanas, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

Fil: Imoberdorf, Gustavo Eduardo. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Instituto de Desarrollo Tecnologico para la Industria Quimica. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnologico para la Industria Quimica; Argentina

A kinetic model for water disinfection employing UV-C radiation was developed that is valid for clear waters as well as for a concentrated and nutritious medium. Escherichia coli was used as a test bacteria. The kinetic model is a modification of the series event inactivation mathematical description that takes into account the radiation absorption rate corresponding to the existing, viable bacteria and the radiation attenuation produced by the quasi transparent or the translucent environment. It also explains two additional observed phenomena: (i) the effect of bacteria growth in the nutritious medium during disinfection and (ii) a further reduction in the inactivation rate that was attributed to some form of bacteria protection produced by a not well understood association of the bacteria with of the components of the concentrated culture. Comparing theoretical predictions from the model with experimental concentration vs. time data, the model parameters were obtained. Predictions show good agreement with collected experimental data within the range of the explored variables. Fil: Labas, Marisol Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Martin, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

The intrinsic reaction kinetics of the photocatalytic decomposition of dichloroacetic acid (DCA) at different, but constant oxygen concentrations was studied. Other significant variables were initial DCA concentration, catalyst (titanium dioxide) concentration and light intensities. The results of the kinetic measurements were analyzed using a complete mathematical model of the experimental device that was used for the laboratory operation (a differential reactor inside a recycle). In this way it was expected to obtain intrinsic kinetic parameters. The kinetic model, that was developed from a proposed complete reaction sequence, has only two lumped specific kinetic constants and represents the dependence of the reaction rate with oxygen, DCA and catalyst concentrations as well as the local volumetric rate of photon absorption. Simulation results are in good agreement with experiments and, at the same time, permit a detailed description of the existing radiation field in the experimental reactor.

The effect of oxygen on the reaction kinetics of the photocatalytic oxidation of dichloroacetic acid at pH below the titanium dioxide isoelectric point (pH from 5 to 4) was studied. A kinetic scheme based on the direct hole attack to the dichloracetate ion in conjunction with the classical role of oxygen acting as an electron acceptor is proposed. Oxygen also intervenes in a direct addition reaction to one of the intermediate reaction products. Experiments were conducted in a well-mixed, small, flat plate reactor employing Aldrich titanium dioxide as the photocatalyst in the suspension mode and using polychromatic irradiation with energy in the range from 275 to 385 nm in wavelength. A complete mathematical model, including the effect of the absorbed radiation intensities and catalyst concentration was developed. Experimental data agree well with theoretical predictions employing just two kinetic parameters derived from the proposed reaction mechanism.

The evaluation of the radiation field inside a slurry reactor constitutes a central step in the study of photocatalytic reactions. This task can be achieved by solving the radiative transfer equation (RTE) for the system under study. To solve the RTE, three optical properties of the catalyst suspensions are needed: the absorption coefficient, the scattering coefficient, and the phase function for scattering. In the present work, a novel experimental method to measure the optical properties of aqueous titanium dioxide (TiO2) suspensions is proposed. The method involved diffuse reflectance and transmittance spectrophotometric measurements of the catalyst suspensions, the evaluation of the radiation field in the sample cell, and the application of a non linear optimization program to adjust model predictions to experimental data. Three commercial brands of TiO2 were investigated: Aldrich, Degussa P25 and Hombikat UV 100. Fil: Satuf, María Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Brandi, Rodolfo Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

Actinometry is an old and useful method developed in the chemistry field to estimate the amount of photons entering and being absorbed in a reaction cell filled with a well-known reacting system. As it is usually used it is of reduced suitability for intrinsic kinetic studies aimed at scaling-up purposes. However, in photochemical reaction engineering analysis it can be of invaluable help if it is properly applied to accurately calculate the boundary condition that is needed to solve the radiative transfer equation in laboratory photochemical reactors dedicated to obtain intrinsic kinetic parameters. This contribution shows the way that actinometric measurements can be used as one of the most precise and simple methods to estimate the above mentioned boundary condition for both homogeneous and heterogeneous systems, an indispensable parameter to calculate with precise models based in the general radiation transport equation, the light distribution inside the reaction space. This local property is needed to formulate the initiation step of any photochemical reaction scheme when operation is made in the kinetic control regime. Consequently it will be always included in any properly developed complete reaction kinetic model. The proposed extended application is illustrated with one example employing a reactor used in photocatalytic reactions. Fil: Zalazar, Cristina Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Labas, Marisol Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Martin, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Brandi, Rodolfo Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

In a previous article, the modeling and experimental verification of the radiation field inside a reactor made of several TiO2 coated, parallel, flat glass fiber meshes, bilaterally UV irradiated was accomplished. The degradation of trichloroethylene (TCE) in an air stream is studied using different values of the pollutant feed concentration, relative humidity and light intensity under operating conditions where kinetic control of the process is established. A kinetic model based on a reaction scheme that involves atomic chlorine as an active reaction intermediate is developed for describing concentration dependencies. It includes, explicitly, the effect of the absorbed light intensity on the rate. The interaction of the existing radiation field with the solid semiconductor to generate electrons, and holes in the reaction catalyst activation step is also modeled. All kinetic parameters are estimated from experiments. The obtained kinetic expression gives a first-order dependence with respect to the TCE concentration and accounts for a competitive effect of water vapor and TCE for the catalyst active sites. An additional important feature of the derived expression is its ability to represent both limiting cases concerning the dependence of the reaction rate with the irradiation rate; that is, order 1 or order 0.5, as well as all possible intermediate values. In fact, the equivalent dependence obtained in this work was 0.6, a value closer to the second case. The results show good agreement between predictions derived from the proposed kinetic expression and TCE experimental concentration data at the reactor's exit. The proposed reactor design provides a practical device for the treatment of contaminated air; it permits a fairly uniform irradiation of the catalytic meshes and a good ratio of the irradiated surface area with respect to the volume of the gaseous reacting mixture. With these features, rather high TCE conversions can be obtained. © 2005 American Institute of Chemical Engineers AIChE J, 2005

A solar photoreactor operated in the batch, recirculating mode is analyzed in terms of very simple observable variables such as the impinging photon flux, the incident area, the initial concentration, the flow rate, the reactor volume and a property defined as the Observed Photonic Efficiency. The proposed equipment is made of a tubular reactor, a tank, a pump and the connecting pipes. The analysis is formulated in terms of the photon input corresponding to an equivalent batch system that is derived as a new reaction coordinate for photoreactions. Employing several plausible approximations, the pollutant concentration evolution in the tank is cast in terms of very simple analytical solutions. Process photonic efficiencies are defined for the system operation and calculated with respect to the maximum achievable yield corresponding to the differential operation of the solar recirculating reactor.

Usual applications of photocatalytic reactors for treating wastewater exhibit the difficulty of handling fluids having varying composition and/or concentrations; thus, a detailed kinetic representation may not be possible. When the catalyst activation is obtained employing solar illumination an additional complexity always coexists: solar fluxes are permanently changing with time. For comparing different reacting systems under similar operating conditions and to provide approximate estimations for scaling up purposes, simplified models may be useful. For these approximations the model parameters should be restricted as much as possible to initial physical and boundary conditions such as: initial concentrations (expressed as such or as TOC measurements), flow rate or reactor volume, irradiated reactor area, incident radiation fluxes and a fairly simple experimental observation such as the photonic efficiency. A combination of a new concept: the “actual observed photonic efficiency” with ideal reactor models and empirical kinetic rate expressions can be used to provide rather simple working equations that can be efficiently used to describe the performance of practical reactors. In this paper, the method has been developed for the case of a photocatalytic batch reactor.

The radiation field in an annular, slurry photocatalytic reactor has been modeled and verified working with a pilot-plant reactor. A suspension of titanium dioxide in water flows through the annular reaction space, which is irradiated with a tubular, UV lamp placed at the central axis of the system. Two different types of titanium dioxide have been used: Aldrich and Degussa P25. Using a rigorous model, it is possible to precisely evaluate the radiation intensity at each point inside the reactor. The radiation distribution was verified by computing the forwardly transmitted radiative fluxes going out of the reactor walls at different axial positions and compared with radiometer measurements (“point” measurements). Predictions of the same fluxes were also verified with homogeneous actinometry employing potassium ferrioxalate (providing an average measurement of the outgoing fluxes over the reactor external surface). When predictions from the theoretical model are compared with experimental data, good agree...

Iron pillared clay (Fe-PILC) was prepared from a montmorillonite and was characterized by scanning electron microscopy and X-ray fluorescence. Fe-PILC catalytic activity was evaluated in photo-Fenton processes applied to the degradation of 2-clorophenol. Different catalyst loads were assayed. The Fe-PILC allowed almost complete degradation of the contaminant. An increase in the contaminant degradation rate was observed, following leaching of iron during catalytic assays, which suggest the existence of a homogeneous photo-Fenton mechanism. The catalytic performance of the Fe-PILC was compared with that for goethite and zero valent iron nanoparticles. Differences were found regarding the achieved degradation levels, the efficiency in oxidant consumption, and the extension of iron leaching. Fil: de León, María A.. Universidad de la República; Uruguay Fil: Sergio, Marta. Universidad de la República; Uruguay Fil: Bussi, Juan. Universidad de la República; Uruguay Fil: Ortiz de la Plata, Guadalupe Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

A spectroscopic and kinetic study of the photo-oxidation of acetaldehyde with a CeO2-TiO2 composite catalyst is presented. Both UV and visible illumination conditions were tested. The study focuses on analysing the role of ceria in the photocatalytic behaviour by contrasting the CeO2-TiO2 behaviour with that of the appropriate TiO2 reference. To this end, we developed an intrinsic kinetic expression with explicit inclusion of the effect of photon absorption on the reaction rate as well as a reaction scheme proposed on the basis of combined Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and Electron Paramagnetic Resonance (EPR) characterization. The combination of spectroscopic and kinetic tools provides quantitative evidence that the oxide-oxide contact controls the activity of the composite catalyst through the number of hole-related species able to attack the pollutant, this in turn being related to the influence of ceria defects on charge carrier fate. The abovementioned key properties controlling photoactivity are the same for UV and visible excitation, producing a highly active photocatalyst suitable for sunlight applications., A. Kubacka and M. J. Muñoz-Batista thank MINECO for support through the postdoctoral “Ramón y Cajal” programs and predoctoral FPI, respectively. M. J. Muñoz-Batista would like to thank MINECO for a grant-in-aid (EEBB-I-13-06684) allowing his stay at Santa Fe, Argentina. Financial support from MINECO is also acknowledged (project CTQ2010-14872/BQU). Also, the authors acknowledge financial support from the Universidad Nacional del Litoral, Agencia Nacional de Promoción Científica y Tecnológica, and Consejo Nacional de Investigaciones Científicas y Técnicas of Argentina.

The kinetics of the photocatalytic decomposition of low concentrations of trichloroethylene (TCE) in water was modeled and the reaction parameters have been evaluated for different catalyst loadings. The employed reactor is a flat plate configuration irradiated by tubular lamps that have emission in the 300–400 nm wavelength range. The mass conservation model is two-dimensional while the developed radiation model is two-dimensional in space and two directional in radiation propagation. The performance of the photoreactor with this reaction can be properly represented employing only two lumped kinetic constants that can be derived from a 12 steps, complete reaction sequence. The deduced kinetic model has explicit functional dependencies for the local volumetric rate of photon absorption (LVRPA) and the effect of the catalyst concentration: r TCE , het ( x ,t)a v =−S g C m , cat α ∫ λ e λ a ( x ,t,C m,cat ) d λ [α 3 C TCE /(1+α 3 C TCE )] . Values of the kinetic constants are: α=1.94×10−9 mol g1/2 cm−2 s−1/2 einstein−1/2 and α3=5.52×106 cm3 mol−1. As derived from the reaction sequence and validated with experiments, it was observed that the reaction rate is proportional to the square root of the LVRPA. The dependence on the catalyst loading, well described by the model, is more complex due to its characteristic effect on the light distribution inside the reaction space.

Water contaminants can be completely mineralized by UV activated powdered TiO2. By recirculating slurried titania through a fluidized bed (FB) of quartz sand, the apparent quantum efficiency of the photocatalyst can be made several fold higher than by just using the suspended powder. Although, in principle, this could be attributed to the re-distribution of the incoming radiation inside the reacting space by the extra scattering centers (the sand grains), and/or the increment of the active catalytic surface through fragmentation of the coalesced TiO2 powder by the collisions among the sand grains and the titania particles, we have found that the latter effect predominates. However, the ionic composition of the aqueous media also plays a key role (via electrostatic interactions between both particulate solids), causing a higher effective concentration of TiO2 inside the reactor. Fil: Pozzo, Roberto Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Giombi, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Baltanás, Miguel A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

A model for scaling up a homogeneous photoreactor was developed and experimentally verified in a pilot-plant-size apparatus. The procedure is exemplified by the oxidation of dilute aqueous HCOOH solutions with UV radiation (254 nm) and H2O2. First, the kinetic model and the kinetic parameters of the HCOOH degradation were obtained in a well-stirred, small, batch flat-plate photoreactor (volume=70 ml). The method employed in the analysis of the experimental results yielded reaction-rate expressions for HCOOH and H2O2 that were independent of the reactor configuration. These kinetic equations and the corresponding kinetic constants were then used in a mathematical, fully deterministic model of a continuous-flow, 2-m-long, annular reactor (0.0065 m2 of cross section for flow) operating in a laminar-flow regime to predict exit concentrations of HCOOH. Irradiation was provided in both cases by two different types of germicidal lamps. No additional experiments were made to adjust the reactor-model parameters. Theoretical predictions from the representation of the reactor performance obtained were compared with experimental data furnished by experiments in the much-larger-size, cylindrical-flow reactor. Results showed good agreement for the range of variables explored; they corresponded to expected operating conditions in water streams polluted with low concentrations of organic compounds.

A simplified mathematical model to describe the oxidative degradation of glyphosate employing hydrogen peroxide and UV radiation was developed based on a sequence of predominant reactions. The kinetics obtained include all the required significant variables. Consequently, not only were concentration dependencies examined but also the influence of a detailed spatial description of the radiation field was included as part of the modeling. The kinetic parameters were obtained by comparing the simulation concentrations obtained with the model with the experimental values gathered in the laboratory reactor, employing a multiparameter non-linear regression analysis. In addition, the potential of the H2O2/UV process for treating water polluted with a commercial formulation, which was the glyphosate monoisopropylamine salt plus some additives, was studied. The glyphosate and TOC (total organic carbon) conversions reached were close to 80% and 70% respectively at 12 h (0.66 h actual exposure to radiation). It has been shown that a simple reaction scheme for the degradation of glyphosate acid and glyphosate isopropylamine salt from a commercial formulation can represent with good accuracy the performance of both reacting systems. In addition, the degradation procedure allowed a clear reduction of the toxicity of the glyphosate in the formulation over Vibrio fischeri at the end of the experiments. For this reason, reaching complete mineralization might not be necessary Fil: Vidal, Eduardo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias; Argentina Fil: Negro, Antonio Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; Argentina Fil: Zalazar, Cristina Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; Argentina

A fixed-bed, annular photoreactor is studied for the photocatalytic disinfection of Escherichia coli aqueous suspensions. Experiments were carried out under UV radiation employing P25 titanium dioxide immobilized onto glass Raschig rings. The photoreactor performance has been simulated following a predicted procedure that takes into account explicitly the radiation absorption step and a series-event disinfection mechanism. The modelling of the radiation field was carried out by Monte Carlo simulation. The reactor model has been compared with experimental data, being able to reproduce the evolution of the concentration of viable bacteria under different bacteria initial concentrations and irradiation levels. Fil: Marugan, Javier. Universidad Rey Juan Carlos; España Fil: Van Grieken, Rafael. Universidad Rey Juan Carlos; España Fil: Pablos, Cristina. Universidad Rey Juan Carlos; España Fil: Satuf, María Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Cassano, Alberto Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Alfano, Orlando Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina