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Johannes A Lercher - One of the best experts on this subject based on the ideXlab platform.

  • surface transport processes and sticking probability of aromatic molecules in hzsm 5
    Journal of Physical Chemistry C, 2008
    Co-Authors: Stephan J Reitmeier, Rino R Mukti, Andreas Jentys, Johannes A Lercher
    Abstract:

    The elementary steps of the Sorption of aromatic molecules such as benzene, toluene, p-xylene, and o-xylene on nonporous amorphous SiO2 (Aerosil) and microporous silicas using HZSM-5 as an example are studied by time-resolved rapid scan IR spectroscopy. Sorption into the zeolite pores proceeds via a weakly bound physisorbed and nonlocalized state on the external surface as the dominating reaction pathway. The weak interaction leads to very low sticking probabilities on the order of 10-7 for porous and nonporous materials alike. Within the molecules investigated, the sticking coefficient increases in the series toluene, o-xylene, benzene, and p-xylene. Using a statistical thermodynamic analysis, this sequence is attributed to the symmetry of the sorbate molecule, the Sorption Enthalpy of the sorbate increasing with the molar mass, and the space the sorbate molecule occupies on the surface.

  • experimental and theoretical investigation of the sticking probability of aromatics on hzsm 5 and sio2
    Studies in Surface Science and Catalysis, 2008
    Co-Authors: Stephan J Reitmeier, Rino R Mukti, Andreas Jentys, Johannes A Lercher
    Abstract:

    Abstract The elementary steps of Sorption and transport of benzene, toluene and p-/o -xylene on MFI-type zeolites were studied by fast time-resolved rapid scan IR spectroscopy. The transport into the zeolite pore proceeds via a weakly bound physisorbed state on the external surface. Due to the weak interaction, very low sticking probabilities in the order of 10 -7 for porous and non-porous materials were observed. The sticking coefficients increased in the series toluene, o -xylene, benzene, and p-xylene, attributed using to the statistical thermodynamic analysis, to the symmetry of the sorbate molecule, the Sorption Enthalpy of the sorbate which increases with molar mass and the space the sorbate molecule occupied on the surface.

Eric Guibal - One of the best experts on this subject based on the ideXlab platform.

  • Effect of agitation mode (mechanical, ultrasound and microwave) on uranium Sorption using amine- and dithizone-functionalized magnetic chitosan hybrid materials
    Chemical Engineering Journal, 2021
    Co-Authors: Khalid Elwakeel, Mohammed Hamza, Eric Guibal
    Abstract:

    Magnetic chitosan nanoparticles, activated by glycidyl methacrylate, can be functionalized by grafting diethylenetriamine (DETA) and dithizone for improving U(VI) Sorption at pH around 5. The physicochemical properties of the materials have been characterized by a wide variety of analytical techniques. Uranyl Sorption increases with the pH (progressive deprotonation of amine and sulfur groups). Uptake kinetics are controlled by the agitation mode: the equilibrium time is reduced while using ultrasonic treatment (especially at highest frequency: 80 kHz): the cavitation effect improves the accessibility to internal reactive groups (Sorption capacity is increased). The diffusivity coefficient is increased by 4–5 times. In the case of microwave, the Sorption capacity is significantly reduced (especially for R-Dithizone, down to 0.8 mmol U g−1) because of temperature increase, which limits the Sorption (exothermic mechanism). Mass transfer is tremendously enhanced: equilibrium time is less than 60 s (30 min for ultrasonic treatment and 120 min with mechanical agitation). Sorption capacity at monolayer saturation (Langmuir) decreases with increasing the temperature from 2.20 to 1.74 mmol U g−1 for R-Amine (from 1.77 to 1.22 mmol U g−1 for R-Dithizone). The Sorption Enthalpy is close to −19.7 kJ mol−1 for R-Amine (with positive entropy change, ΔS°) and −34.2 kJ mol−1 for R-Dithizone (negative ΔS°). Metal deSorption is highly efficient using 0.3 M Na2CO3 /0.1 M H2O2 solution. Metal deSorption is instantaneous (less than 1 min) and complete when using microwave treatment. The ultrasonic treatment allows improving deSorption efficiency and decreasing the concentration of the eluent compared with mechanical agitation. The process is successfully applied for uranyl separation from the leachates of marine sediments, especially in the presence of Complexon III (masking agent).

Stephan J Reitmeier - One of the best experts on this subject based on the ideXlab platform.

  • surface transport processes and sticking probability of aromatic molecules in hzsm 5
    Journal of Physical Chemistry C, 2008
    Co-Authors: Stephan J Reitmeier, Rino R Mukti, Andreas Jentys, Johannes A Lercher
    Abstract:

    The elementary steps of the Sorption of aromatic molecules such as benzene, toluene, p-xylene, and o-xylene on nonporous amorphous SiO2 (Aerosil) and microporous silicas using HZSM-5 as an example are studied by time-resolved rapid scan IR spectroscopy. Sorption into the zeolite pores proceeds via a weakly bound physisorbed and nonlocalized state on the external surface as the dominating reaction pathway. The weak interaction leads to very low sticking probabilities on the order of 10-7 for porous and nonporous materials alike. Within the molecules investigated, the sticking coefficient increases in the series toluene, o-xylene, benzene, and p-xylene. Using a statistical thermodynamic analysis, this sequence is attributed to the symmetry of the sorbate molecule, the Sorption Enthalpy of the sorbate increasing with the molar mass, and the space the sorbate molecule occupies on the surface.

  • experimental and theoretical investigation of the sticking probability of aromatics on hzsm 5 and sio2
    Studies in Surface Science and Catalysis, 2008
    Co-Authors: Stephan J Reitmeier, Rino R Mukti, Andreas Jentys, Johannes A Lercher
    Abstract:

    Abstract The elementary steps of Sorption and transport of benzene, toluene and p-/o -xylene on MFI-type zeolites were studied by fast time-resolved rapid scan IR spectroscopy. The transport into the zeolite pore proceeds via a weakly bound physisorbed state on the external surface. Due to the weak interaction, very low sticking probabilities in the order of 10 -7 for porous and non-porous materials were observed. The sticking coefficients increased in the series toluene, o -xylene, benzene, and p-xylene, attributed using to the statistical thermodynamic analysis, to the symmetry of the sorbate molecule, the Sorption Enthalpy of the sorbate which increases with molar mass and the space the sorbate molecule occupied on the surface.

Khalid Elwakeel - One of the best experts on this subject based on the ideXlab platform.

  • Effect of agitation mode (mechanical, ultrasound and microwave) on uranium Sorption using amine- and dithizone-functionalized magnetic chitosan hybrid materials
    Chemical Engineering Journal, 2021
    Co-Authors: Khalid Elwakeel, Mohammed Hamza, Eric Guibal
    Abstract:

    Magnetic chitosan nanoparticles, activated by glycidyl methacrylate, can be functionalized by grafting diethylenetriamine (DETA) and dithizone for improving U(VI) Sorption at pH around 5. The physicochemical properties of the materials have been characterized by a wide variety of analytical techniques. Uranyl Sorption increases with the pH (progressive deprotonation of amine and sulfur groups). Uptake kinetics are controlled by the agitation mode: the equilibrium time is reduced while using ultrasonic treatment (especially at highest frequency: 80 kHz): the cavitation effect improves the accessibility to internal reactive groups (Sorption capacity is increased). The diffusivity coefficient is increased by 4–5 times. In the case of microwave, the Sorption capacity is significantly reduced (especially for R-Dithizone, down to 0.8 mmol U g−1) because of temperature increase, which limits the Sorption (exothermic mechanism). Mass transfer is tremendously enhanced: equilibrium time is less than 60 s (30 min for ultrasonic treatment and 120 min with mechanical agitation). Sorption capacity at monolayer saturation (Langmuir) decreases with increasing the temperature from 2.20 to 1.74 mmol U g−1 for R-Amine (from 1.77 to 1.22 mmol U g−1 for R-Dithizone). The Sorption Enthalpy is close to −19.7 kJ mol−1 for R-Amine (with positive entropy change, ΔS°) and −34.2 kJ mol−1 for R-Dithizone (negative ΔS°). Metal deSorption is highly efficient using 0.3 M Na2CO3 /0.1 M H2O2 solution. Metal deSorption is instantaneous (less than 1 min) and complete when using microwave treatment. The ultrasonic treatment allows improving deSorption efficiency and decreasing the concentration of the eluent compared with mechanical agitation. The process is successfully applied for uranyl separation from the leachates of marine sediments, especially in the presence of Complexon III (masking agent).

Rino R Mukti - One of the best experts on this subject based on the ideXlab platform.

  • surface transport processes and sticking probability of aromatic molecules in hzsm 5
    Journal of Physical Chemistry C, 2008
    Co-Authors: Stephan J Reitmeier, Rino R Mukti, Andreas Jentys, Johannes A Lercher
    Abstract:

    The elementary steps of the Sorption of aromatic molecules such as benzene, toluene, p-xylene, and o-xylene on nonporous amorphous SiO2 (Aerosil) and microporous silicas using HZSM-5 as an example are studied by time-resolved rapid scan IR spectroscopy. Sorption into the zeolite pores proceeds via a weakly bound physisorbed and nonlocalized state on the external surface as the dominating reaction pathway. The weak interaction leads to very low sticking probabilities on the order of 10-7 for porous and nonporous materials alike. Within the molecules investigated, the sticking coefficient increases in the series toluene, o-xylene, benzene, and p-xylene. Using a statistical thermodynamic analysis, this sequence is attributed to the symmetry of the sorbate molecule, the Sorption Enthalpy of the sorbate increasing with the molar mass, and the space the sorbate molecule occupies on the surface.

  • experimental and theoretical investigation of the sticking probability of aromatics on hzsm 5 and sio2
    Studies in Surface Science and Catalysis, 2008
    Co-Authors: Stephan J Reitmeier, Rino R Mukti, Andreas Jentys, Johannes A Lercher
    Abstract:

    Abstract The elementary steps of Sorption and transport of benzene, toluene and p-/o -xylene on MFI-type zeolites were studied by fast time-resolved rapid scan IR spectroscopy. The transport into the zeolite pore proceeds via a weakly bound physisorbed state on the external surface. Due to the weak interaction, very low sticking probabilities in the order of 10 -7 for porous and non-porous materials were observed. The sticking coefficients increased in the series toluene, o -xylene, benzene, and p-xylene, attributed using to the statistical thermodynamic analysis, to the symmetry of the sorbate molecule, the Sorption Enthalpy of the sorbate which increases with molar mass and the space the sorbate molecule occupied on the surface.