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Jeanmichel Laine - One of the best experts on this subject based on the ideXlab platform.
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effect of hydrogen peroxide on the destruction of organic contaminants synergism and inhibition in a continuous mode photocatalytic reactor
Applied Catalysis B-environmental, 2004Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Jeanmichel LaineAbstract:Abstract The effect of hydrogen peroxide on the photocatalytic degradation of organic contaminants in water was investigated using a TiO 2 -rotating disk photocatalytic reactor (RDPR) operated in a continuous-mode and at steady state. The experiments were performed at pH 3.0, in the presence of near-UV radiation, and using 4-Chlorobenzoic Acid (4-CBA) as a model non-volatile organic contaminant at influent concentration of 300 μmol l −1 . Experiments were performed at concentrations of hydrogen peroxide in the range 0–10.74 mmol l −1 . Addition of hydrogen peroxide at small concentrations ( −1 ) had a synergistic effect and increased considerably the rates of photocatalytic reactions. An optimum influent hydrogen peroxide concentration was observed at 1.6 mmol l −1 , which caused an increased in the rates of 4-CBA degradation and total organic carbon (TOC) mineralization by 1.72 and 2.13 times, respectively. This corresponded to an optimum oxidant to contaminant molar ratio of 5.33. At higher concentrations, hydrogen peroxide was found to cause an inhibiting effect on the photocatalytic reactions. The synergistic and inhibiting effects of hydrogen peroxide were rationalized based on the reaction rate constants between relevant radical species.
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effect of hydrogen peroxide on the destruction of organic contaminants synergism and inhibition in a continuous mode photocatalytic reactor
Applied Catalysis B-environmental, 2004Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Jeanmichel LaineAbstract:Abstract The effect of hydrogen peroxide on the photocatalytic degradation of organic contaminants in water was investigated using a TiO2-rotating disk photocatalytic reactor (RDPR) operated in a continuous-mode and at steady state. The experiments were performed at pH 3.0, in the presence of near-UV radiation, and using 4-Chlorobenzoic Acid (4-CBA) as a model non-volatile organic contaminant at influent concentration of 300 μmol l−1. Experiments were performed at concentrations of hydrogen peroxide in the range 0–10.74 mmol l−1. Addition of hydrogen peroxide at small concentrations (
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oxidation of organic contaminants in a rotating disk photocatalytic reactor reaction kinetics in the liquid phase and the role of mass transfer based on the dimensionless damkohler number
Applied Catalysis B-environmental, 2002Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Jeanmichel LaineAbstract:Abstract The photocatalytic degradation of a model non-volatile chlorinated aromatic compound 4-Chlorobenzoic Acid (4-CBA) was investigated as a function of disk angular velocity, contaminant concentration, and incident light intensity using a rotating disk photocatalytic reactor (RDPR). The study was designed to investigate the effect of all three parameters on the degradation rate as well as their importance on unveiling the existence of mass transfer limitations in the liquid phase under specific conditions. The results showed that the reaction rate increased with disk angular velocity in accordance with a saturation-type dependency. In the range of 2–6 rpm the degradation rate increased almost linearly with disk angular velocity. Above 6 rpm, however, the influence of disk angular velocity was not significant. The initial increase in the reaction rate with disk angular velocity was attributed to the longer time available per rotation resulting in higher down flow of liquid carried by the disk and to the increase in the overall mass transfer coefficient. The rates of 4-CBA Acid decomposition and Cl− mineralization at 6 rpm as a function of initial 4-CBA concentration followed Langmuir–Hinshelwood kinetics. At 6 rpm, the rates of 4-CBA degradation followed a linear dependency with incident light intensity. This was attributed to the existence of low local values of incident light intensity on the illuminated disk. With respect to the effect of these three parameters on the degradation rate, the obtained results suggested the absence of significant mass transfer limitations at disk angular velocities higher than 6 rpm. The latter was verified by additional calculations of the Damkohler (Da) number based on dimensionless analysis. The Da number was found to decrease significantly with disk angular velocity and at high disk angular velocities (ω>15 rpm), Da was much lower than 0.1, even when the concentration of the contaminant in the bulk was extremely small (i.e. 1 μmol/l).
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tio2 assisted photocatalytic degradation of 4 Chlorobenzoic Acid in water effect of type of catalyst catalyst loading initial contaminant concentration and solution characteristics
Water Science & Technology: Water Supply, 2001Co-Authors: Dionysios D. Dionysiou, Jeanmichel Laine, Isabelle Baudin, Makram T. Suidan, T. L. HuangAbstract:Photocatalytic degradation of 4-Chlorobenzoic Acid in water was studied using different TiO 2 catalysts (Degussa P-25, Ishihara ST01 and Hombikat UV-100) and solution characteristics. Mineralization of 4-Chlorobenzoic Acid was achieved in all the experiments and total recovery of the chlorine as free Cl - was obtained. The catalyst concentration influenced the photocatalytic rates and the optimum loading concentration was determined to be different for Degussa P-25 and Ishihara ST01, mainly due to the difference in their adsorption and scattering characteristics. Comparison between the catalysts for their photocatalytic activity revealed that other factors must influence the photocatalytic reaction rates beside the surface area of the catalysts. The photocatalytic reaction rates were found to obey the Langmuir-Hinshelwood adsorptionreaction model. At pH = 7.0, the presence of Cl did not inhibit the reaction rates. At pH = 3.0, however, the photocatalytic reaction rates were higher for the solution containing NO - 3 instead of Cl - at the same molar concentration.
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rotating disk photocatalytic reactor development characterization and evaluation for the destruction of organic pollutants in water
Water Research, 2000Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Ganesh Balasubramanian, Amid P Khodadoust, Jeanmichel LaineAbstract:This work focuses on the development, characterization and evaluation of the TiO2 Rotating Disk Photocatalytic Reactor (RDPR) for the treatment of organic pollutants in water. A commercial TiO2-based catalyst in the form of composite ceramic balls was used as the immobilized photocatalyst on the rotating disk. LiCl tracer studies conducted at different disk angular velocities, ranging from 20 to 5 rpm, proved that the mixing in the RDPR is close to that of an ideal CSTR. Two different techniques, an overflow method and the potassium ferrioxalate actinometry method were employed for determining the liquid holdup and turnover time of the rotating disk with glass beads substituted for TiO2 coated beads. The two methods were in agreement and only the overflow method was employed for determining the same parameters for the rotating disk when loaded with TiO2 composite ceramic balls. Power law correlations were obtained in all cases. TiO2-assisted photocatalytic degradation of 4-Chlorobenzoic Acid (4-CBA) was investigated in the RDPR at a specified angular velocity of the rotating disk (4 rpm), initial pH=3.0, and room temperature using near-UV radiation.
Dionysios D. Dionysiou - One of the best experts on this subject based on the ideXlab platform.
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correlation of structural properties and film thickness to photocatalytic activity of thick tio2 films coated on stainless steel
Applied Catalysis B-environmental, 2006Co-Authors: Yongjun Chen, Dionysios D. DionysiouAbstract:Abstract A transparent, relatively dense and thick TiO 2 film with good mechanical properties and enhanced photocatalytic activity has been successfully immobilized on 304 stainless steel. The study included optimization of structural properties and film thickness. Experiments on the photocatalytic degradation of 4-Chlorobenzoic Acid (4-CBA) as a model organic contaminant showed that the photocatalytic activity of this kind of thick film can be significantly improved by decreasing calcination temperature (i.e. from 600 to 500 °C), which is due to an increase in BET surface area and porosity, decrease in crystal size, and decrease in foreign metal diffusion from stainless steel support to the surface of the film. The observed apparent rate constant of TiO 2 -500 (500 °C, two dip coating layers) was found to be approximately 5.2 times that of TiO 2 -600 (600 °C, two dip coating layers). The results showed that increasing film thickness within a certain range (up to 10 μm) could significantly improve the photocatalytic activity without causing crack formation for the thick TiO 2 -500 film (500 °C). The optimum film thickness is 10 μm (four dip coating cycles), under which the observed apparent rate constant of TiO 2 -500 is approximately 2.3 times higher than that of TiO 2 -500 with 2.5 μm film thickness (one dip coating layer). Based on several advantages of TiO 2 -500 film (500 °C, four dip coating layers), including high photocatalytic activity, absence of foreign metal ions at the film surface, optimum film thickness, good structural integrity, and excellent adhesion on the stainless steel support, this kind of sol–gel-derived thick film immobilized on stainless steel support is a promising potential photocatalyst for water treatment applications.
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effect of hydrogen peroxide on the destruction of organic contaminants synergism and inhibition in a continuous mode photocatalytic reactor
Applied Catalysis B-environmental, 2004Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Jeanmichel LaineAbstract:Abstract The effect of hydrogen peroxide on the photocatalytic degradation of organic contaminants in water was investigated using a TiO 2 -rotating disk photocatalytic reactor (RDPR) operated in a continuous-mode and at steady state. The experiments were performed at pH 3.0, in the presence of near-UV radiation, and using 4-Chlorobenzoic Acid (4-CBA) as a model non-volatile organic contaminant at influent concentration of 300 μmol l −1 . Experiments were performed at concentrations of hydrogen peroxide in the range 0–10.74 mmol l −1 . Addition of hydrogen peroxide at small concentrations ( −1 ) had a synergistic effect and increased considerably the rates of photocatalytic reactions. An optimum influent hydrogen peroxide concentration was observed at 1.6 mmol l −1 , which caused an increased in the rates of 4-CBA degradation and total organic carbon (TOC) mineralization by 1.72 and 2.13 times, respectively. This corresponded to an optimum oxidant to contaminant molar ratio of 5.33. At higher concentrations, hydrogen peroxide was found to cause an inhibiting effect on the photocatalytic reactions. The synergistic and inhibiting effects of hydrogen peroxide were rationalized based on the reaction rate constants between relevant radical species.
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effect of hydrogen peroxide on the destruction of organic contaminants synergism and inhibition in a continuous mode photocatalytic reactor
Applied Catalysis B-environmental, 2004Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Jeanmichel LaineAbstract:Abstract The effect of hydrogen peroxide on the photocatalytic degradation of organic contaminants in water was investigated using a TiO2-rotating disk photocatalytic reactor (RDPR) operated in a continuous-mode and at steady state. The experiments were performed at pH 3.0, in the presence of near-UV radiation, and using 4-Chlorobenzoic Acid (4-CBA) as a model non-volatile organic contaminant at influent concentration of 300 μmol l−1. Experiments were performed at concentrations of hydrogen peroxide in the range 0–10.74 mmol l−1. Addition of hydrogen peroxide at small concentrations (
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oxidation of organic contaminants in a rotating disk photocatalytic reactor reaction kinetics in the liquid phase and the role of mass transfer based on the dimensionless damkohler number
Applied Catalysis B-environmental, 2002Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Jeanmichel LaineAbstract:Abstract The photocatalytic degradation of a model non-volatile chlorinated aromatic compound 4-Chlorobenzoic Acid (4-CBA) was investigated as a function of disk angular velocity, contaminant concentration, and incident light intensity using a rotating disk photocatalytic reactor (RDPR). The study was designed to investigate the effect of all three parameters on the degradation rate as well as their importance on unveiling the existence of mass transfer limitations in the liquid phase under specific conditions. The results showed that the reaction rate increased with disk angular velocity in accordance with a saturation-type dependency. In the range of 2–6 rpm the degradation rate increased almost linearly with disk angular velocity. Above 6 rpm, however, the influence of disk angular velocity was not significant. The initial increase in the reaction rate with disk angular velocity was attributed to the longer time available per rotation resulting in higher down flow of liquid carried by the disk and to the increase in the overall mass transfer coefficient. The rates of 4-CBA Acid decomposition and Cl− mineralization at 6 rpm as a function of initial 4-CBA concentration followed Langmuir–Hinshelwood kinetics. At 6 rpm, the rates of 4-CBA degradation followed a linear dependency with incident light intensity. This was attributed to the existence of low local values of incident light intensity on the illuminated disk. With respect to the effect of these three parameters on the degradation rate, the obtained results suggested the absence of significant mass transfer limitations at disk angular velocities higher than 6 rpm. The latter was verified by additional calculations of the Damkohler (Da) number based on dimensionless analysis. The Da number was found to decrease significantly with disk angular velocity and at high disk angular velocities (ω>15 rpm), Da was much lower than 0.1, even when the concentration of the contaminant in the bulk was extremely small (i.e. 1 μmol/l).
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tio2 assisted photocatalytic degradation of 4 Chlorobenzoic Acid in water effect of type of catalyst catalyst loading initial contaminant concentration and solution characteristics
Water Science & Technology: Water Supply, 2001Co-Authors: Dionysios D. Dionysiou, Jeanmichel Laine, Isabelle Baudin, Makram T. Suidan, T. L. HuangAbstract:Photocatalytic degradation of 4-Chlorobenzoic Acid in water was studied using different TiO 2 catalysts (Degussa P-25, Ishihara ST01 and Hombikat UV-100) and solution characteristics. Mineralization of 4-Chlorobenzoic Acid was achieved in all the experiments and total recovery of the chlorine as free Cl - was obtained. The catalyst concentration influenced the photocatalytic rates and the optimum loading concentration was determined to be different for Degussa P-25 and Ishihara ST01, mainly due to the difference in their adsorption and scattering characteristics. Comparison between the catalysts for their photocatalytic activity revealed that other factors must influence the photocatalytic reaction rates beside the surface area of the catalysts. The photocatalytic reaction rates were found to obey the Langmuir-Hinshelwood adsorptionreaction model. At pH = 7.0, the presence of Cl did not inhibit the reaction rates. At pH = 3.0, however, the photocatalytic reaction rates were higher for the solution containing NO - 3 instead of Cl - at the same molar concentration.
Isabelle Baudin - One of the best experts on this subject based on the ideXlab platform.
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effect of hydrogen peroxide on the destruction of organic contaminants synergism and inhibition in a continuous mode photocatalytic reactor
Applied Catalysis B-environmental, 2004Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Jeanmichel LaineAbstract:Abstract The effect of hydrogen peroxide on the photocatalytic degradation of organic contaminants in water was investigated using a TiO 2 -rotating disk photocatalytic reactor (RDPR) operated in a continuous-mode and at steady state. The experiments were performed at pH 3.0, in the presence of near-UV radiation, and using 4-Chlorobenzoic Acid (4-CBA) as a model non-volatile organic contaminant at influent concentration of 300 μmol l −1 . Experiments were performed at concentrations of hydrogen peroxide in the range 0–10.74 mmol l −1 . Addition of hydrogen peroxide at small concentrations ( −1 ) had a synergistic effect and increased considerably the rates of photocatalytic reactions. An optimum influent hydrogen peroxide concentration was observed at 1.6 mmol l −1 , which caused an increased in the rates of 4-CBA degradation and total organic carbon (TOC) mineralization by 1.72 and 2.13 times, respectively. This corresponded to an optimum oxidant to contaminant molar ratio of 5.33. At higher concentrations, hydrogen peroxide was found to cause an inhibiting effect on the photocatalytic reactions. The synergistic and inhibiting effects of hydrogen peroxide were rationalized based on the reaction rate constants between relevant radical species.
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effect of hydrogen peroxide on the destruction of organic contaminants synergism and inhibition in a continuous mode photocatalytic reactor
Applied Catalysis B-environmental, 2004Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Jeanmichel LaineAbstract:Abstract The effect of hydrogen peroxide on the photocatalytic degradation of organic contaminants in water was investigated using a TiO2-rotating disk photocatalytic reactor (RDPR) operated in a continuous-mode and at steady state. The experiments were performed at pH 3.0, in the presence of near-UV radiation, and using 4-Chlorobenzoic Acid (4-CBA) as a model non-volatile organic contaminant at influent concentration of 300 μmol l−1. Experiments were performed at concentrations of hydrogen peroxide in the range 0–10.74 mmol l−1. Addition of hydrogen peroxide at small concentrations (
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oxidation of organic contaminants in a rotating disk photocatalytic reactor reaction kinetics in the liquid phase and the role of mass transfer based on the dimensionless damkohler number
Applied Catalysis B-environmental, 2002Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Jeanmichel LaineAbstract:Abstract The photocatalytic degradation of a model non-volatile chlorinated aromatic compound 4-Chlorobenzoic Acid (4-CBA) was investigated as a function of disk angular velocity, contaminant concentration, and incident light intensity using a rotating disk photocatalytic reactor (RDPR). The study was designed to investigate the effect of all three parameters on the degradation rate as well as their importance on unveiling the existence of mass transfer limitations in the liquid phase under specific conditions. The results showed that the reaction rate increased with disk angular velocity in accordance with a saturation-type dependency. In the range of 2–6 rpm the degradation rate increased almost linearly with disk angular velocity. Above 6 rpm, however, the influence of disk angular velocity was not significant. The initial increase in the reaction rate with disk angular velocity was attributed to the longer time available per rotation resulting in higher down flow of liquid carried by the disk and to the increase in the overall mass transfer coefficient. The rates of 4-CBA Acid decomposition and Cl− mineralization at 6 rpm as a function of initial 4-CBA concentration followed Langmuir–Hinshelwood kinetics. At 6 rpm, the rates of 4-CBA degradation followed a linear dependency with incident light intensity. This was attributed to the existence of low local values of incident light intensity on the illuminated disk. With respect to the effect of these three parameters on the degradation rate, the obtained results suggested the absence of significant mass transfer limitations at disk angular velocities higher than 6 rpm. The latter was verified by additional calculations of the Damkohler (Da) number based on dimensionless analysis. The Da number was found to decrease significantly with disk angular velocity and at high disk angular velocities (ω>15 rpm), Da was much lower than 0.1, even when the concentration of the contaminant in the bulk was extremely small (i.e. 1 μmol/l).
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tio2 assisted photocatalytic degradation of 4 Chlorobenzoic Acid in water effect of type of catalyst catalyst loading initial contaminant concentration and solution characteristics
Water Science & Technology: Water Supply, 2001Co-Authors: Dionysios D. Dionysiou, Jeanmichel Laine, Isabelle Baudin, Makram T. Suidan, T. L. HuangAbstract:Photocatalytic degradation of 4-Chlorobenzoic Acid in water was studied using different TiO 2 catalysts (Degussa P-25, Ishihara ST01 and Hombikat UV-100) and solution characteristics. Mineralization of 4-Chlorobenzoic Acid was achieved in all the experiments and total recovery of the chlorine as free Cl - was obtained. The catalyst concentration influenced the photocatalytic rates and the optimum loading concentration was determined to be different for Degussa P-25 and Ishihara ST01, mainly due to the difference in their adsorption and scattering characteristics. Comparison between the catalysts for their photocatalytic activity revealed that other factors must influence the photocatalytic reaction rates beside the surface area of the catalysts. The photocatalytic reaction rates were found to obey the Langmuir-Hinshelwood adsorptionreaction model. At pH = 7.0, the presence of Cl did not inhibit the reaction rates. At pH = 3.0, however, the photocatalytic reaction rates were higher for the solution containing NO - 3 instead of Cl - at the same molar concentration.
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rotating disk photocatalytic reactor development characterization and evaluation for the destruction of organic pollutants in water
Water Research, 2000Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Ganesh Balasubramanian, Amid P Khodadoust, Jeanmichel LaineAbstract:This work focuses on the development, characterization and evaluation of the TiO2 Rotating Disk Photocatalytic Reactor (RDPR) for the treatment of organic pollutants in water. A commercial TiO2-based catalyst in the form of composite ceramic balls was used as the immobilized photocatalyst on the rotating disk. LiCl tracer studies conducted at different disk angular velocities, ranging from 20 to 5 rpm, proved that the mixing in the RDPR is close to that of an ideal CSTR. Two different techniques, an overflow method and the potassium ferrioxalate actinometry method were employed for determining the liquid holdup and turnover time of the rotating disk with glass beads substituted for TiO2 coated beads. The two methods were in agreement and only the overflow method was employed for determining the same parameters for the rotating disk when loaded with TiO2 composite ceramic balls. Power law correlations were obtained in all cases. TiO2-assisted photocatalytic degradation of 4-Chlorobenzoic Acid (4-CBA) was investigated in the RDPR at a specified angular velocity of the rotating disk (4 rpm), initial pH=3.0, and room temperature using near-UV radiation.
Makram T. Suidan - One of the best experts on this subject based on the ideXlab platform.
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effect of hydrogen peroxide on the destruction of organic contaminants synergism and inhibition in a continuous mode photocatalytic reactor
Applied Catalysis B-environmental, 2004Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Jeanmichel LaineAbstract:Abstract The effect of hydrogen peroxide on the photocatalytic degradation of organic contaminants in water was investigated using a TiO 2 -rotating disk photocatalytic reactor (RDPR) operated in a continuous-mode and at steady state. The experiments were performed at pH 3.0, in the presence of near-UV radiation, and using 4-Chlorobenzoic Acid (4-CBA) as a model non-volatile organic contaminant at influent concentration of 300 μmol l −1 . Experiments were performed at concentrations of hydrogen peroxide in the range 0–10.74 mmol l −1 . Addition of hydrogen peroxide at small concentrations ( −1 ) had a synergistic effect and increased considerably the rates of photocatalytic reactions. An optimum influent hydrogen peroxide concentration was observed at 1.6 mmol l −1 , which caused an increased in the rates of 4-CBA degradation and total organic carbon (TOC) mineralization by 1.72 and 2.13 times, respectively. This corresponded to an optimum oxidant to contaminant molar ratio of 5.33. At higher concentrations, hydrogen peroxide was found to cause an inhibiting effect on the photocatalytic reactions. The synergistic and inhibiting effects of hydrogen peroxide were rationalized based on the reaction rate constants between relevant radical species.
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effect of hydrogen peroxide on the destruction of organic contaminants synergism and inhibition in a continuous mode photocatalytic reactor
Applied Catalysis B-environmental, 2004Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Jeanmichel LaineAbstract:Abstract The effect of hydrogen peroxide on the photocatalytic degradation of organic contaminants in water was investigated using a TiO2-rotating disk photocatalytic reactor (RDPR) operated in a continuous-mode and at steady state. The experiments were performed at pH 3.0, in the presence of near-UV radiation, and using 4-Chlorobenzoic Acid (4-CBA) as a model non-volatile organic contaminant at influent concentration of 300 μmol l−1. Experiments were performed at concentrations of hydrogen peroxide in the range 0–10.74 mmol l−1. Addition of hydrogen peroxide at small concentrations (
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oxidation of organic contaminants in a rotating disk photocatalytic reactor reaction kinetics in the liquid phase and the role of mass transfer based on the dimensionless damkohler number
Applied Catalysis B-environmental, 2002Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Jeanmichel LaineAbstract:Abstract The photocatalytic degradation of a model non-volatile chlorinated aromatic compound 4-Chlorobenzoic Acid (4-CBA) was investigated as a function of disk angular velocity, contaminant concentration, and incident light intensity using a rotating disk photocatalytic reactor (RDPR). The study was designed to investigate the effect of all three parameters on the degradation rate as well as their importance on unveiling the existence of mass transfer limitations in the liquid phase under specific conditions. The results showed that the reaction rate increased with disk angular velocity in accordance with a saturation-type dependency. In the range of 2–6 rpm the degradation rate increased almost linearly with disk angular velocity. Above 6 rpm, however, the influence of disk angular velocity was not significant. The initial increase in the reaction rate with disk angular velocity was attributed to the longer time available per rotation resulting in higher down flow of liquid carried by the disk and to the increase in the overall mass transfer coefficient. The rates of 4-CBA Acid decomposition and Cl− mineralization at 6 rpm as a function of initial 4-CBA concentration followed Langmuir–Hinshelwood kinetics. At 6 rpm, the rates of 4-CBA degradation followed a linear dependency with incident light intensity. This was attributed to the existence of low local values of incident light intensity on the illuminated disk. With respect to the effect of these three parameters on the degradation rate, the obtained results suggested the absence of significant mass transfer limitations at disk angular velocities higher than 6 rpm. The latter was verified by additional calculations of the Damkohler (Da) number based on dimensionless analysis. The Da number was found to decrease significantly with disk angular velocity and at high disk angular velocities (ω>15 rpm), Da was much lower than 0.1, even when the concentration of the contaminant in the bulk was extremely small (i.e. 1 μmol/l).
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tio2 assisted photocatalytic degradation of 4 Chlorobenzoic Acid in water effect of type of catalyst catalyst loading initial contaminant concentration and solution characteristics
Water Science & Technology: Water Supply, 2001Co-Authors: Dionysios D. Dionysiou, Jeanmichel Laine, Isabelle Baudin, Makram T. Suidan, T. L. HuangAbstract:Photocatalytic degradation of 4-Chlorobenzoic Acid in water was studied using different TiO 2 catalysts (Degussa P-25, Ishihara ST01 and Hombikat UV-100) and solution characteristics. Mineralization of 4-Chlorobenzoic Acid was achieved in all the experiments and total recovery of the chlorine as free Cl - was obtained. The catalyst concentration influenced the photocatalytic rates and the optimum loading concentration was determined to be different for Degussa P-25 and Ishihara ST01, mainly due to the difference in their adsorption and scattering characteristics. Comparison between the catalysts for their photocatalytic activity revealed that other factors must influence the photocatalytic reaction rates beside the surface area of the catalysts. The photocatalytic reaction rates were found to obey the Langmuir-Hinshelwood adsorptionreaction model. At pH = 7.0, the presence of Cl did not inhibit the reaction rates. At pH = 3.0, however, the photocatalytic reaction rates were higher for the solution containing NO - 3 instead of Cl - at the same molar concentration.
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rotating disk photocatalytic reactor development characterization and evaluation for the destruction of organic pollutants in water
Water Research, 2000Co-Authors: Dionysios D. Dionysiou, Isabelle Baudin, Makram T. Suidan, Ganesh Balasubramanian, Amid P Khodadoust, Jeanmichel LaineAbstract:This work focuses on the development, characterization and evaluation of the TiO2 Rotating Disk Photocatalytic Reactor (RDPR) for the treatment of organic pollutants in water. A commercial TiO2-based catalyst in the form of composite ceramic balls was used as the immobilized photocatalyst on the rotating disk. LiCl tracer studies conducted at different disk angular velocities, ranging from 20 to 5 rpm, proved that the mixing in the RDPR is close to that of an ideal CSTR. Two different techniques, an overflow method and the potassium ferrioxalate actinometry method were employed for determining the liquid holdup and turnover time of the rotating disk with glass beads substituted for TiO2 coated beads. The two methods were in agreement and only the overflow method was employed for determining the same parameters for the rotating disk when loaded with TiO2 composite ceramic balls. Power law correlations were obtained in all cases. TiO2-assisted photocatalytic degradation of 4-Chlorobenzoic Acid (4-CBA) was investigated in the RDPR at a specified angular velocity of the rotating disk (4 rpm), initial pH=3.0, and room temperature using near-UV radiation.
Pierre Pichat - One of the best experts on this subject based on the ideXlab platform.
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probing multiple effects of tio2 sintering temperature on photocatalytic activity in water by use of a series of organic pollutant molecules
Catalysis Today, 2007Co-Authors: Rosario Enriquez, Alexander G Agrios, Pierre PichatAbstract:Abstract Our goal was to determine whether changes induced in TiO2 by sintering have a net effect on the photocatalytic removal rate of trace organics in water that depends on the organic. To that end, we have used (i) commercialized TiO2 samples prepared by varying the sintering temperature of the parent TiO2; (ii) several probe molecules: phenol, anisole, 4-chlorophenol, 2,5-dichlorophenol, 4-Chlorobenzoic Acid, pyridine and dichloroacetic Acid. For aromatics, except pyridine, the removal rates increased with sintering temperature, whereas the opposite was true for pyridine (with one exception) and dichloroacetic Acid. These results can be interpreted on the basis of the following hypotheses: decarboxylation requires direct pollutant–TiO2 contact; pyridine can react by formation of a N-centered radical cation; photocatalytic hydroxylation can occur within the near-surface solution layers. This last hypothesis was checked by comparing the removal rates of some of the probes over powdered TiO2 to rates over TiO2 coatings where the accessibility to the TiO2 surface was restricted by a SiO2 binder. In practice, the consequences are that one test pollutant does not suffice to quantitatively compare photocatalytic activities, and the selection of an optimal TiO2 sintering temperature for photocatalytic water treatment depends on the target pollutant(s).
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different net effect of tio2 sintering temperature on the photocatalytic removal rates of 4 chlorophenol 4 Chlorobenzoic Acid and dichloroacetic Acid in water
Journal of Environmental Science and Health Part A-toxic\ hazardous Substances & Environmental Engineering, 2006Co-Authors: Rosario Enriquez, Pierre PichatAbstract:Our purpose was to show that the sintering temperature of TiO2 can have a different net effect (thought to arise from a decrease in surface area against a decrease in recombination rate of charge carriers) on the photocatalytic removal rate of various organic pollutants in water. For that, we have chosen four chlorinated pollutants, viz. 4-chlorophenol (4-CP), 2,5-dichlorophenol (2,5-DCP), 4-Chlorobenzoic Acid (4-CBA) and dichloroacetic Acid (DCAA). Their photocatalytic removal was studied over four TiO2 samples (from Millennium Chemicals or affiliate) all obtained identically by TiOSO4 thermohydrolysis with subsequent calcination at various temperatures, TiO2 Degussa P25 was used for comparison. At equal TiO2 mass in the slurry photoreactor, the pseudo-first-order removal rate constant k increased with the calcination temperatures for the three aromatic pollutants, whereas it was the opposite for the aliphatic Acid. Results obtained with P25 were consistent with the reasoning based on the combined effect...
