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Dessy Wulandari - One of the best experts on this subject based on the ideXlab platform.
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zno montmorillonite for photocatalytic and Photochemical Degradation of methylene blue
Applied Clay Science, 2011Co-Authors: Is Fatimah, Shaobin Wang, Dessy WulandariAbstract:Synthesis of a ZnO/montmorillonite photocatalyst based on an Indonesian natural montmorillonite was conducted using a sol–gel intercalation method. The physicochemical properties of the material were determined by XRD, N2 adsorption–desorption, SEM, TEM and UV–Vis diffuse reflectance. The activity was evaluated in photocatalytic and Photochemical Degradation of methylene blue (MB) with and without H2O2. Characterization showed that the ZnO particles were successfully distributed in montmorillonite support and ZnO/montmorillonite had lower band gap energy. The increased adsorption of MB on ZnO/montmorillonite resulted in faster photoDegradation. The kinetics of the reaction obeyed the Langmuir–Hinshelwood model.
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ZnO/montmorillonite for photocatalytic and Photochemical Degradation of methylene blue
Applied Clay Science, 2011Co-Authors: Is Fatimah, Shaobin Wang, Dessy WulandariAbstract:Synthesis of a ZnO/montmorillonite photocatalyst based on an Indonesian natural montmorillonite was conducted using a sol–gel intercalation method. The physicochemical properties of the material were determined by XRD, N2 adsorption–desorption, SEM, TEM and UV–Vis diffuse reflectance. The activity was evaluated in photocatalytic and Photochemical Degradation of methylene blue (MB) with and without H2O2. Characterization showed that the ZnO particles were successfully distributed in montmorillonite support and ZnO/montmorillonite had lower band gap energy. The increased adsorption of MB on ZnO/montmorillonite resulted in faster photoDegradation. The kinetics of the reaction obeyed the Langmuir–Hinshelwood model.
David R. Tyler - One of the best experts on this subject based on the ideXlab platform.
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Metal–metal bond photochemistry as a tool for understanding the Photochemical Degradation of plastics
Inorganica Chimica Acta, 2015Co-Authors: David R. TylerAbstract:Abstract Research from the author’s laboratory is reviewed on the photochemistry of polymers that have metal–metal bonds incorporated into their backbones. These polymers are useful for studying the mechanistic aspects of polymer photoDegradation because irradiation with visible light causes photolysis of the metal–metal bonds with subsequent Degradation of the polymer backbone. The relative simplicity of the Degradation process in these polymers facilitates detailed mechanistic studies. In contrast, the Degradation pathways in “regular” polymers are intricate, and consequently it is difficult to do detailed mechanistic studies of photoDegradation. Two mechanistic studies involving the metal–metal-bond-containing polymers are reviewed. The first study investigated why the kinetics of Photochemical Degradation are biphasic. Using the polymers with metal–metal bonds, it was shown that the biphasic kinetics arise because the Photochemically generated radicals are initially formed in one of two environments. In one environment, a radical trap is within the immediate reactive sphere of the radical; in the other environment, no radical trap is present. The second study examined the temperature dependence of the Photochemical Degradation reactions in the polymers. The temperature dependence was shown to arise from secondary chain movements of the polymers. It is emphasized that similar studies using regular polymers would have been more difficult to carry out and interpret.
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Mechanistic Aspects of the Effects of Stress on the Rates of Photochemical Degradation Reactions in Polymers
Journal of Macromolecular Science Part C: Polymer Reviews, 2004Co-Authors: David R. TylerAbstract:Abstract This review examines the mechanistic origins of the effects of stress on the Photochemical Degradation rates of polymers. Recent studies have shown that tensile and shear stresses accelerate the rate of the Photochemical Degradation of polymers. Conversely, compressive stress generally retards the rate of Photochemical Degradation. After an initial discussion of the Photochemical auto‐oxidation mechanism, the three primary hypotheses that purport to explain how stress affects Photochemical Degradation are examined. The first hypothesis is attributed to Plotnikov, who proposed that stress changes the quantum yields of the reactions that lead to bond photolysis. The second hypothesis, attributed to a number of researchers, says that stress affects the ability of the geminate radical pairs, formed in the Photochemical bond cleavage reactions, to recombine. The third hypothesis proposes that stress changes the rates of radical reactions subsequent to radical formation. A further attempt to account fo...
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Investigation of the origin of tensile stress-induced rate enhancements in the Photochemical Degradation of polymers.
Journal of the American Chemical Society, 2004Co-Authors: Rui Chen, Myungok Yoon, Arwyn L. E. Smalley, David C. Johnson, David R. TylerAbstract:To investigate the effect of tensile stress on the Photochemical Degradation efficiencies of polymers, a modified PVC polymer with Cp(CO)3Mo−Mo(CO)3Cp (Cp = η5-C5H5) units along the backbone was synthesized. The polymer is Photochemically reactive because the Mo−Mo bonds are photolyzed with visible light and the resulting radicals are captured with Cl atoms from along the polymer backbone. Of most importance from a mechanistic standpoint, the Photochemical Degradation reaction occurs in the absence of oxygen, which eliminates the kinetically complicating effect of rate-limiting oxygen diffusion. Tensile stress initially caused the quantum yield of polymer Degradation to increase, but, after a certain point, additional stress caused a decrease in the quantum yield. This dependence of quantum efficiency on stress is consistent with a hypothesis in which stress affects the ability of the Photochemically generated radicals to recombine. At low to moderate stress, the effect of stress is to increase the separa...
Is Fatimah - One of the best experts on this subject based on the ideXlab platform.
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zno montmorillonite for photocatalytic and Photochemical Degradation of methylene blue
Applied Clay Science, 2011Co-Authors: Is Fatimah, Shaobin Wang, Dessy WulandariAbstract:Synthesis of a ZnO/montmorillonite photocatalyst based on an Indonesian natural montmorillonite was conducted using a sol–gel intercalation method. The physicochemical properties of the material were determined by XRD, N2 adsorption–desorption, SEM, TEM and UV–Vis diffuse reflectance. The activity was evaluated in photocatalytic and Photochemical Degradation of methylene blue (MB) with and without H2O2. Characterization showed that the ZnO particles were successfully distributed in montmorillonite support and ZnO/montmorillonite had lower band gap energy. The increased adsorption of MB on ZnO/montmorillonite resulted in faster photoDegradation. The kinetics of the reaction obeyed the Langmuir–Hinshelwood model.
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ZnO/montmorillonite for photocatalytic and Photochemical Degradation of methylene blue
Applied Clay Science, 2011Co-Authors: Is Fatimah, Shaobin Wang, Dessy WulandariAbstract:Synthesis of a ZnO/montmorillonite photocatalyst based on an Indonesian natural montmorillonite was conducted using a sol–gel intercalation method. The physicochemical properties of the material were determined by XRD, N2 adsorption–desorption, SEM, TEM and UV–Vis diffuse reflectance. The activity was evaluated in photocatalytic and Photochemical Degradation of methylene blue (MB) with and without H2O2. Characterization showed that the ZnO particles were successfully distributed in montmorillonite support and ZnO/montmorillonite had lower band gap energy. The increased adsorption of MB on ZnO/montmorillonite resulted in faster photoDegradation. The kinetics of the reaction obeyed the Langmuir–Hinshelwood model.
Jieshan Qiu - One of the best experts on this subject based on the ideXlab platform.
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Effects of excited-state structures and properties on Photochemical Degradation of polybrominated diphenyl ethers: a TDDFT study.
Chemosphere, 2012Co-Authors: Wang, Ce Hao, Zhanxian Gao, Jingwen Chen, Jieshan QiuAbstract:Abstract This study presents new insight into the Photochemical Degradation of polybrominated diphenyl ethers (PBDEs), and it provides details about the structures and properties of 27 PBDE congeners in the electronically excited state using the time-dependent density functional theory method. Each PBDE congener exhibited remarkably different geometries in the ground state and the excited state. The significant lengthening of C–Br bond in each PBDE congener was observed in the excited state for the first time by theoretical calculation, which is directly involved in the photochemistry reductive debromination of n-BDE to (n−1)-BDE. Generally, the lengthening of C–Br bonds cannot occur at the para position. Furthermore, the calculated results demonstrated that the photoreactivity of PBDEs increased with an increase of bromination degree. It was also found that the pattern of Br substituents had an effect upon the photoreactivity of PBDEs. These findings suggest that the information obtained in the excited state is crucial to the mechanism explanation of the Photochemical Degradation of PBDEs.
Shaobin Wang - One of the best experts on this subject based on the ideXlab platform.
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zno montmorillonite for photocatalytic and Photochemical Degradation of methylene blue
Applied Clay Science, 2011Co-Authors: Is Fatimah, Shaobin Wang, Dessy WulandariAbstract:Synthesis of a ZnO/montmorillonite photocatalyst based on an Indonesian natural montmorillonite was conducted using a sol–gel intercalation method. The physicochemical properties of the material were determined by XRD, N2 adsorption–desorption, SEM, TEM and UV–Vis diffuse reflectance. The activity was evaluated in photocatalytic and Photochemical Degradation of methylene blue (MB) with and without H2O2. Characterization showed that the ZnO particles were successfully distributed in montmorillonite support and ZnO/montmorillonite had lower band gap energy. The increased adsorption of MB on ZnO/montmorillonite resulted in faster photoDegradation. The kinetics of the reaction obeyed the Langmuir–Hinshelwood model.
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ZnO/montmorillonite for photocatalytic and Photochemical Degradation of methylene blue
Applied Clay Science, 2011Co-Authors: Is Fatimah, Shaobin Wang, Dessy WulandariAbstract:Synthesis of a ZnO/montmorillonite photocatalyst based on an Indonesian natural montmorillonite was conducted using a sol–gel intercalation method. The physicochemical properties of the material were determined by XRD, N2 adsorption–desorption, SEM, TEM and UV–Vis diffuse reflectance. The activity was evaluated in photocatalytic and Photochemical Degradation of methylene blue (MB) with and without H2O2. Characterization showed that the ZnO particles were successfully distributed in montmorillonite support and ZnO/montmorillonite had lower band gap energy. The increased adsorption of MB on ZnO/montmorillonite resulted in faster photoDegradation. The kinetics of the reaction obeyed the Langmuir–Hinshelwood model.