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Wei Chu - One of the best experts on this subject based on the ideXlab platform.
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Monuron photodegradation using peroxymonosulfate activated by non metal doped tio2 under visible led and the modeling via a parallel serial kinetic approach
Chemical Engineering Journal, 2018Co-Authors: Amal Abdelhaleem, Wei ChuAbstract:Abstract N-doped TiO2 (NT) was proven to be efficient for Monuron decay via peroxymonosulfate (PMS) activation under visible LED (Vis LED). The activation mechanism revealed that OH and SO4− have a critical role in the Monuron decay with a ratio of about 3 to 1, respectively; and the holes at the catalyst surface are the main precursors in forming SO4− . The NT/PMS/Vis LED hybrid process was found to be an effective approach under a wide solution pH range of 2.5–9.2 (>80% decay). Interestingly, the highest efficiency was observed at pH 9.2 due to the contribution of PMS/Vis LED process by generating both OH and SO4− at alkaline pH. However, the decay rate of Monuron was inhibited at pH 11.6 due to the dissociation of OH into O− and the electrostatic repulsion among reagents. The process was also suitable for ion-rich wastewater since no significant reduction in the performance was induced in the presence of high concentrations of inorganic anions. Furthermore, the process was proven to be a promising approach for mineralization of Monuron and its intermediates. Twenty reaction intermediates were detected and five of them are newly reported. A novel mathematical model was established based on reaction intermediates using a parallel-serial-irreversible reaction approach, which is helpful in predicting the detoxification extent of hazardous intermediates.
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photocatalytic oxidation of Monuron in the suspension of wo3 under the irradiation of uv visible light
Chemosphere, 2012Co-Authors: Wei Chu, Y F RaoAbstract:Abstract A comprehensive study of the degradation of Monuron, one of the phenylurea herbicides, was conducted by UV–Vis/WO3 process. It was found that hydroxyl radicals played a major role in the decay of Monuron while other radicals (e.g. superoxide) and hole might also contribute to the decomposition of Monuron. The oxidation path likely plays a major role in the generation of hydroxyl radicals. The effects of initial pH level, initial concentration of Monuron, and inorganic oxidants on the performance of UV–Vis/WO3 process were also investigated and optimized. Comparison between Monuron decay pathways by UV–Vis/WO3 and UV/TiO2 was conducted. The decay mechanisms, including N-terminus demethylation, dechlorination and direct hydroxylation on benzene ring, were observed to be involved in the oxidation of Monuron in these two processes. Sixteen intermediates were identified during the photodegradation of Monuron and degradation pathways were proposed accordingly.
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riboflavin sensitized photooxidation of phenylurea herbicide Monuron in aqueous peroxide solution
Chemical Engineering Journal, 2009Co-Authors: K. H. Chan, Wei ChuAbstract:Abstract A natural photosensitizer riboflavin (Rf), known as vitamin B 2 , and an environmental friendly strong oxidant hydrogen peroxide (H 2 O 2 ) were employed for the riboflavin-sensitized photooxidation process (UV/Rf/H 2 O 2 ) in this study. This approach could be considered as a hybrid process of UV/Rf (photosensitization) and UV/H 2 O 2 (advanced oxidation). The photodecay of a phenylurea herbicide Monuron was investigated by varying the doses of Rf and H 2 O 2 in this work. The use of UV/Rf/H 2 O 2 showed a promising performance for degrading Monuron compared with the direct photolysis (UV), UV/Rf, and UV/H 2 O 2 processes. It was found that more than 99% of the Monuron was removed in the UV/Rf/H 2 O 2 process in less than 70 min depending on the dosages of Rf and H 2 O 2 . In general, the overall improvement of UV/Rf/H 2 O 2 process would achieve as high as ∼450% comparing to sole-UV process. In addition, a kinetic model for the UV/Rf/H 2 O 2 process was developed successfully in this study to facilitate the prediction of the additional performance on the degradation of Monuron comparing with the daughter processes (UV, UV/Rf, and UV/H 2 O 2 ).
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Removal of phenylurea herbicide Monuron via riboflavin-mediated photosensitization.
Chemosphere, 2007Co-Authors: Wei Chu, K. H. Chan, Chad T. Jafvert, Yuk Sing Gilbert ChanAbstract:Abstract Photodegradation of the phenylurea herbicide Monuron by using riboflavin (Rf), a sensitizer, was investigated by varying the doses of Monuron and Rf in this work. An enhanced photochemical effect was observed in the process compared with the direct photolysis by using UV irradiation only. The reaction time was greatly shortened from more than 60 min (direct photolysis) to 8–30 min depending on the doses of initial concentration of Monuron ([M]0) and Rf. A modified hyperbola model was found to be useful to determine the reaction kinetics and thereafter the performance on the photodegradation of Monuron sensitized by Rf. Two measurable characteristic constants (initial decay rate and total removal index) were used to quantify the reaction. The maximum removal difference compared with the direct photolysis and Rf-sensitization was investigated. It was found that the improvement of the process depended on both the [M]0 and the doses of Rf.
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selection of supported cobalt substrates in the presence of oxone for the oxidation of Monuron
Journal of Agricultural and Food Chemistry, 2007Co-Authors: Wei Chu, Wk Choy, Cy KwanAbstract:The immobilization of cobalt ion on different media to catalyze oxone has been investigated. A probe herbicide, Monuron, was effectively degraded by using Co2+/oxone systems. For Co2+ supported on ...
K. H. Chan - One of the best experts on this subject based on the ideXlab platform.
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riboflavin sensitized photooxidation of phenylurea herbicide Monuron in aqueous peroxide solution
Chemical Engineering Journal, 2009Co-Authors: K. H. Chan, Wei ChuAbstract:Abstract A natural photosensitizer riboflavin (Rf), known as vitamin B 2 , and an environmental friendly strong oxidant hydrogen peroxide (H 2 O 2 ) were employed for the riboflavin-sensitized photooxidation process (UV/Rf/H 2 O 2 ) in this study. This approach could be considered as a hybrid process of UV/Rf (photosensitization) and UV/H 2 O 2 (advanced oxidation). The photodecay of a phenylurea herbicide Monuron was investigated by varying the doses of Rf and H 2 O 2 in this work. The use of UV/Rf/H 2 O 2 showed a promising performance for degrading Monuron compared with the direct photolysis (UV), UV/Rf, and UV/H 2 O 2 processes. It was found that more than 99% of the Monuron was removed in the UV/Rf/H 2 O 2 process in less than 70 min depending on the dosages of Rf and H 2 O 2 . In general, the overall improvement of UV/Rf/H 2 O 2 process would achieve as high as ∼450% comparing to sole-UV process. In addition, a kinetic model for the UV/Rf/H 2 O 2 process was developed successfully in this study to facilitate the prediction of the additional performance on the degradation of Monuron comparing with the daughter processes (UV, UV/Rf, and UV/H 2 O 2 ).
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Riboflavin-sensitized photooxidation of phenylurea herbicide Monuron in aqueous peroxide solution
Elsevier, 2009Co-Authors: K. H. Chan, Chu WAbstract:A natural photosensitizer riboflavin (Rf), known as vitamin B2, and an environmental friendly strong oxidant hydrogen peroxide (H2O2) were employed for the riboflavin-sensitized photooxidation process (UV/Rf/H2O2) in this study. This approach could be considered as a hybrid process of UV/Rf (photosensitization) and UV/H2O2 (advanced oxidation). The photodecay of a phenylurea herbicide Monuron was investigated by varying the doses of Rf and H2O2 in this work. The use of UV/Rf/H2O2 showed a promising performance for degrading Monuron compared with the direct photolysis (UV), UV/Rf, and UV/H2O2 processes. It was found that more than 99% of the Monuron was removed in the UV/Rf/H2O2 process in less than 70 min depending on the dosages of Rf and H2O2. In general, the overall improvement of UV/Rf/H2O2 process would achieve as high as ∼450% comparing to sole-UV process. In addition, a kinetic model for the UV/Rf/H2O2 process was developed successfully in this study to facilitate the prediction of the additional performance on the degradation of Monuron comparing with the daughter processes (UV, UV/Rf, and UV/H2O2).Department of Civil and Environmental Engineerin
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Removal of phenylurea herbicide Monuron via riboflavin-mediated photosensitization.
Chemosphere, 2007Co-Authors: Wei Chu, K. H. Chan, Chad T. Jafvert, Yuk Sing Gilbert ChanAbstract:Abstract Photodegradation of the phenylurea herbicide Monuron by using riboflavin (Rf), a sensitizer, was investigated by varying the doses of Monuron and Rf in this work. An enhanced photochemical effect was observed in the process compared with the direct photolysis by using UV irradiation only. The reaction time was greatly shortened from more than 60 min (direct photolysis) to 8–30 min depending on the doses of initial concentration of Monuron ([M]0) and Rf. A modified hyperbola model was found to be useful to determine the reaction kinetics and thereafter the performance on the photodegradation of Monuron sensitized by Rf. Two measurable characteristic constants (initial decay rate and total removal index) were used to quantify the reaction. The maximum removal difference compared with the direct photolysis and Rf-sensitization was investigated. It was found that the improvement of the process depended on both the [M]0 and the doses of Rf.
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hybrid system to upgrade conventional fenton s process by incorporating photo fenton as a successive treatment process degradation of Monuron
Industrial & Engineering Chemistry Research, 2007Co-Authors: Wei Chu, K. H. ChanAbstract:The degradation of Monuron in different remediation processes including UV, UV/H2O2, Fenton's process (FP), and photo-Fenton's process (UV/FP) was investigated, and then a hybrid system was proposed based on the results. The processes of UV and UV/H2O2 were found to completely remove the Monuron, but a longer irradiation time was required. For the FP, a rapid decay of Monuron was observed at the beginning of the process but a complete removal was difficult unless very high doses of reagents were used, and negative effects from overdose could be observed. For the UV/FP, both the rapid decay and complete removal of Monuron were observed. However, it may not be as cost-effective as the UV irradiation because higher energy consumption was involved. Thus, a new approach on upgrading conventional FP by incorporating UV/FP as a successive treatment process was proposed in this work. This hybrid system could improve the initial decay rate and performance of FP and reduce the power consumption compared to that in ...
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Hybrid system to upgrade conventional fenton's process by incorporating photo-fenton as a successive treatment process : degradation of Monuron
American Chemical Society, 2007Co-Authors: Chu W, K. H. ChanAbstract:The degradation of Monuron in different remediation processes including UV, UV/H2O2, Fenton's process (FP), and photo-Fenton's process (UV/FP) was investigated, and then a hybrid system was proposed based on the results. The processes of UV and UV/H2O2 were found to completely remove the Monuron, but a longer irradiation time was required. For the FP, a rapid decay of Monuron was observed at the beginning of the process but a complete removal was difficult unless very high doses of reagents were used, and negative effects from overdose could be observed. For the UV/FP, both the rapid decay and complete removal of Monuron were observed. However, it may not be as cost-effective as the UV irradiation because higher energy consumption was involved. Thus, a new approach on upgrading conventional FP by incorporating UV/FP as a successive treatment process was proposed in this work. This hybrid system could improve the initial decay rate and performance of FP and reduce the power consumption compared to that in the original UV/FP. A hybrid model equation was developed and found to be very useful for predicting the degradation of Monuron in the hybrid system.Department of Civil and Environmental Engineerin
Michele Bolte - One of the best experts on this subject based on the ideXlab platform.
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effect of iron speciation on the photodegradation of Monuron in combined photocatalytic systems with immobilized or suspended tio2
Environmental Chemistry Letters, 2009Co-Authors: Gilles Mailhot, Josef Krýsa, Jaromir Jirkovský, Hana Měsťankova, Michele BolteAbstract:Photodegradation kinetics of Monuron (3-(4-chlorophenyl)-1,1-dimethylurea) in photoreactor with immobilized and suspended TiO2 photocatalyst were studied. The effect of addition of ferric or ferrous perchlorate was investigated. Whatever the concentration of Fe(III/II) added there is no significant negative effect on the photodegradation rate of pollutants. On the contrary, depending on speciation and concentration of iron salts, slight or marked acceleration of the photodegradation kinetics was observed. This positive influence was more pronounced in the case of TiO2 suspensions than for TiO2 layers. Fe(III) was generally more effective than Fe(II).
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the influence of fe iii speciation on supported tio2 efficiency example of Monuron photocatalytic degradation
Applied Catalysis B-environmental, 2005Co-Authors: Gilles Mailhot, Josef Krýsa, Jaromir Jirkovský, H Městankova, Michele BolteAbstract:Abstract The degradation of herbicide Monuron (initial concentration 5×10−5 M) in plate photoreactor with laminar flow of the solution using heterogeneous (TiO2) and/or homogeneous photocatalyst (Fe(ClO4)3) was investigated. For the rate of photoinduced degradation with Fe(III) aquacomplexes, the initial concentration of monomer Fe(OH)2+, which is the most photocatalytically active form of Fe(III), is crucial. The degradation rate for combination of both photocatalysts is higher than the sum of the rates for separately taken single catalysts. This is caused not only by the addition of the two effects but also by the fact that Fe(III) acts as scavanger of electrons photogenerated in TiO2 particles thus let down hole–electron recombination. Fe(OH)2+ appears to be the most photoactive trap for electrons.
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mineralisation of Monuron photoinduced by fe iii in aqueous solution
Chemosphere, 2004Co-Authors: Hana Městankova, Gilles Mailhot, Jeanfrancois Pilichowski, Josef Krýsa, Jaromir Jirkovský, Michele BolteAbstract:Abstract The degradation of Monuron (3-(4-chlorophenyl)-1,1-dimethylurea) photoinduced by Fe(III) in aqueous solution has been investigated. The rate of degradation depends on the concentration of Fe(OH) 2+ , the most photoreactive species in terms of OH radical formation. These OH radicals are able to degrade Monuron until total mineralisation. The primordial role of the speciation of Fe(III)-hydroxy complex in aqueous solution, for the efficiency of the elimination of pollutant, was shown and explained in detail. The formation of Fe(II) in the irradiated solution was monitored and correlated with the total organic carbon evolution. Degradation photoproducts were identified and a mechanism of degradation is proposed.
Josef Krýsa - One of the best experts on this subject based on the ideXlab platform.
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effect of iron speciation on the photodegradation of Monuron in combined photocatalytic systems with immobilized or suspended tio2
Environmental Chemistry Letters, 2009Co-Authors: Gilles Mailhot, Josef Krýsa, Jaromir Jirkovský, Hana Měsťankova, Michele BolteAbstract:Photodegradation kinetics of Monuron (3-(4-chlorophenyl)-1,1-dimethylurea) in photoreactor with immobilized and suspended TiO2 photocatalyst were studied. The effect of addition of ferric or ferrous perchlorate was investigated. Whatever the concentration of Fe(III/II) added there is no significant negative effect on the photodegradation rate of pollutants. On the contrary, depending on speciation and concentration of iron salts, slight or marked acceleration of the photodegradation kinetics was observed. This positive influence was more pronounced in the case of TiO2 suspensions than for TiO2 layers. Fe(III) was generally more effective than Fe(II).
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photocatalytic degradation of model organic pollutants on an immobilized particulate tio2 layer roles of adsorption processes and mechanistic complexity
Applied Catalysis B-environmental, 2006Co-Authors: Josef Krýsa, Hana Městankova, Jaromir Jirkovský, Georg Waldner, Gottfried GrabnerAbstract:Abstract The kinetics of photocatalytic degradation of four different model organic compounds, formic acid (FA), oxalic acid (OA), 4-chlorophenol (4-CP) and the herbicide Monuron (3-(4-chlorophenyl)-1,1-dimethylurea) in a self-constructed batch-mode plate photoreactor with a thin flow of contaminated aqueous solution circulating over an illuminated particulate layer of TiO2 P25 (Degussa) was compared. Both OA and FA were adsorbed on TiO2 surface; their mineralization, induced by direct transfer of photogenerated holes, proceeded in a single step, without observable intermediates, following approximately zero order kinetics. Numerical simulations were performed using a newly proposed kinetic model based on the photostationary state assumption. The model allowed an explanation of the observed reaction order as well as the comparison of independent with competitive adsorption of organic compound and oxygen on the photocatalyst surface, yielding a better fit for the case of competition. 4-CP and Monuron, which were not adsorbed under the conditions used, were degraded through the action of photogenerated hydroxyl radicals. Their degradation proceeded with lower photoefficiency than for the adsorbed compounds (FA and OA). While the mineralization of both 4-CP and Monuron followed zero order kinetics, their degradation was close to first order. The different reaction orders were consistently explained using the photostationary state approach.
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the influence of fe iii speciation on supported tio2 efficiency example of Monuron photocatalytic degradation
Applied Catalysis B-environmental, 2005Co-Authors: Gilles Mailhot, Josef Krýsa, Jaromir Jirkovský, H Městankova, Michele BolteAbstract:Abstract The degradation of herbicide Monuron (initial concentration 5×10−5 M) in plate photoreactor with laminar flow of the solution using heterogeneous (TiO2) and/or homogeneous photocatalyst (Fe(ClO4)3) was investigated. For the rate of photoinduced degradation with Fe(III) aquacomplexes, the initial concentration of monomer Fe(OH)2+, which is the most photocatalytically active form of Fe(III), is crucial. The degradation rate for combination of both photocatalysts is higher than the sum of the rates for separately taken single catalysts. This is caused not only by the addition of the two effects but also by the fact that Fe(III) acts as scavanger of electrons photogenerated in TiO2 particles thus let down hole–electron recombination. Fe(OH)2+ appears to be the most photoactive trap for electrons.
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mineralisation of Monuron photoinduced by fe iii in aqueous solution
Chemosphere, 2004Co-Authors: Hana Městankova, Gilles Mailhot, Jeanfrancois Pilichowski, Josef Krýsa, Jaromir Jirkovský, Michele BolteAbstract:Abstract The degradation of Monuron (3-(4-chlorophenyl)-1,1-dimethylurea) photoinduced by Fe(III) in aqueous solution has been investigated. The rate of degradation depends on the concentration of Fe(OH) 2+ , the most photoreactive species in terms of OH radical formation. These OH radicals are able to degrade Monuron until total mineralisation. The primordial role of the speciation of Fe(III)-hydroxy complex in aqueous solution, for the efficiency of the elimination of pollutant, was shown and explained in detail. The formation of Fe(II) in the irradiated solution was monitored and correlated with the total organic carbon evolution. Degradation photoproducts were identified and a mechanism of degradation is proposed.
Gilles Mailhot - One of the best experts on this subject based on the ideXlab platform.
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effect of iron speciation on the photodegradation of Monuron in combined photocatalytic systems with immobilized or suspended tio2
Environmental Chemistry Letters, 2009Co-Authors: Gilles Mailhot, Josef Krýsa, Jaromir Jirkovský, Hana Měsťankova, Michele BolteAbstract:Photodegradation kinetics of Monuron (3-(4-chlorophenyl)-1,1-dimethylurea) in photoreactor with immobilized and suspended TiO2 photocatalyst were studied. The effect of addition of ferric or ferrous perchlorate was investigated. Whatever the concentration of Fe(III/II) added there is no significant negative effect on the photodegradation rate of pollutants. On the contrary, depending on speciation and concentration of iron salts, slight or marked acceleration of the photodegradation kinetics was observed. This positive influence was more pronounced in the case of TiO2 suspensions than for TiO2 layers. Fe(III) was generally more effective than Fe(II).
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the influence of fe iii speciation on supported tio2 efficiency example of Monuron photocatalytic degradation
Applied Catalysis B-environmental, 2005Co-Authors: Gilles Mailhot, Josef Krýsa, Jaromir Jirkovský, H Městankova, Michele BolteAbstract:Abstract The degradation of herbicide Monuron (initial concentration 5×10−5 M) in plate photoreactor with laminar flow of the solution using heterogeneous (TiO2) and/or homogeneous photocatalyst (Fe(ClO4)3) was investigated. For the rate of photoinduced degradation with Fe(III) aquacomplexes, the initial concentration of monomer Fe(OH)2+, which is the most photocatalytically active form of Fe(III), is crucial. The degradation rate for combination of both photocatalysts is higher than the sum of the rates for separately taken single catalysts. This is caused not only by the addition of the two effects but also by the fact that Fe(III) acts as scavanger of electrons photogenerated in TiO2 particles thus let down hole–electron recombination. Fe(OH)2+ appears to be the most photoactive trap for electrons.
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mineralisation of Monuron photoinduced by fe iii in aqueous solution
Chemosphere, 2004Co-Authors: Hana Městankova, Gilles Mailhot, Jeanfrancois Pilichowski, Josef Krýsa, Jaromir Jirkovský, Michele BolteAbstract:Abstract The degradation of Monuron (3-(4-chlorophenyl)-1,1-dimethylurea) photoinduced by Fe(III) in aqueous solution has been investigated. The rate of degradation depends on the concentration of Fe(OH) 2+ , the most photoreactive species in terms of OH radical formation. These OH radicals are able to degrade Monuron until total mineralisation. The primordial role of the speciation of Fe(III)-hydroxy complex in aqueous solution, for the efficiency of the elimination of pollutant, was shown and explained in detail. The formation of Fe(II) in the irradiated solution was monitored and correlated with the total organic carbon evolution. Degradation photoproducts were identified and a mechanism of degradation is proposed.