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  • Küçük Resim Yok
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    Adsorption mechanisms investigation of methylene blue on the (001) zeolite 4A surface in aqueous medium by computational approach and molecular dynamics
    (Elsevier, 2022) Khnifira, M.; El Hamidi, S.; Sadiq, M.; Simsek, S.; Kaya, S.; Barka, N.; Abdennouri, M.
    The cationic methylene blue (CMB) and its pmtonated forms have been studied by computational tools to predict their adsorption behavior on zeolite 4A. The interaction nature has been exhaustively studied in terms of energy gap (Delta E-g), global reactivity descriptors, Fukui functions, adsorption energy, density of states and natural bond orbital analysis. It was found that the protonated CMB (N36N35) molecule is less stable, more electmphilic and very reactive. The highest contribution to the lowering of the stabilization energy (E-2) for all systems was mainly due to the intramolecular charge transfer from the lone pair of the nitrogen atoms as a donor orbital to pi* as an acceptor orbital. DFT calculations revealed that N36 and N35 site of CMB was faced with a lower energy gap (Delta E-g) and chemical hardness (eta) as well as a higher electron accepting power compared to other sites. Monte Carlo molecular modeling simulation (MCMM) confirmed the predominant of electrostatic interactions and p-p electron coupling. The studied compounds prefer to have configurations that facilitate p-p interaction, which is evident from the parallel orientation of CMB with zeolite surface. The dynamic parameters show that the adsorption of methylene blue is exothermic and spontaneous chemisorption.
  • Küçük Resim Yok
    Öğe
    Removal and regeneration of As(V) in aqueous solutions by adsorption on calcined fluorapatite
    (Springer, 2023) Billah, R. E. K.; Kaya, S.; Simsek, S.; Halim, E. M.; Agunaou, M.; Soufiane, A.
    Herein, Fluorapatite has been calcined and successfully applied for the removal of As(VI). The materials prepared have been characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Thermogravimetric analysis and point zero charge pH were also considered as part of these characterizations. Several parameters affecting the adsorption process were studied in this work, such as the mass, time, pH, and the initial concentration effect. The experimental data were modeled using kinetics (pseudo-first-order, PS1 and pseudo-second-order, PS2) and isotherm (Langmuir and Freundlich) models to understand the mechanism related to the uptake process. As(V) uptake was relatively rapid and was highly dependent on pH. The pseudo-second-order rate expression supported data best, while the Langmuir equation could satisfactorily describe isotherm data. Finally, Fluorapatite calcined has been successfully reused for more than 5 cycles without significant loss of its sorption capacity.