Browsing by Author "Tuncel, Duygu"

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    Adsorption Mechanisms, Kinetics and Photoactivities of Green Synthesized Hydroxyapatite Supported Zno and La-Zno Catalysts
    (Pergamon-elsevier Science Ltd, 2024) Tuncel Turan, Duygu; Okte, A. Neren; Temel Eczacılık Bilimleri Bölümü
    In this study, hydroxyapatite (HAP) is synthesized by a co-precipitation method from the waste eggshell, utilized as a support for ZnO (ZnO-HAP) and La-ZnO (La-ZnO-HAP) and employed to degrade methyl orange (MO) and methylene blue (MB) dyes under UV irradiation. Water vapor adsorption as relative humidity (84 % RH) on the HAP structure and the as-prepared catalysts are also examined. The characteristic ZnO and HAP reflections are detected in X-ray diffraction (XRD) analysis of ZnO-HAP, La-ZnO-HAP and humidified samples. ZnO and La-ZnO existence is also verified by scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis, UV-Vis diffuse reflectance (UV-Vis DRS) spectra and X-ray photoelectron spectra (XPS). ZnO and La-ZnO loading on the HAP induce the formation of mesoporous structures with high surface areas. Dark adsorption capacities and photoactivities of the as-prepared samples are explored regarding electrostatic interactions, Lewis acid-base interactions and hydrogen bonding for both MO and MB. In particular, La-ZnO-HAP 500 degrees C and La-ZnO-HAP 500 degrees C (RH) exhibit improved adsorption abilities and photoactivities. The pseudo-second order model describes the kinetic behavior of all samples under dark conditions. Unhumidified samples follow Langmuir isotherm while Freundlich isotherm better fits humidified ones. Under irradiation, the Langmuir-Hinshelwood kinetic model describes the photoactivities of all samples. The four recycling tests confirm the stabilities of HAP 100 degrees C, HAP 500 degrees C, ZnO-HAP 500 degrees C and La-ZnO-HAP 500 degrees C. This study suggests that the ZnO or La-ZnO loaded HAP catalysts prepared in the presence and absence of humid conditions are considered promising materials for environmental remediation.
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    TiO2@ZIF-8 Hybrid as a Type II Heterojunction Photocatalyst:Adsorption/Photocatalytic Properties, Kinetics, and Effect of Humidity
    (Springernature, 2025) Okte, A. Neren; Tuncel, Duygu
    TiO2@ZIF-8 hybrid and its humidified forms are synthesized as type 2 heterojunction systems using a facile sol-gel method at different relative humidity (RH) conditions. The hybrids' surface characteristics and optical properties are thoroughly examined, followed by investigations into adsorption capacities and photocatalytic activities using anionic-methyl orange (MO) and cationic-methylene blue (MB) dyes. TiO2@ZIF-8 hybrid generates a mesoporous structure with a higher surface area (135.6 m2 g-1) than bare TiO2 (40.1 m2 g-1). Band gap energies of TiO2@ZIF-8 (3.00 eV) and humidified hybrids (2.95-2.91 eV) decrease compared to the individual phases of TiO2 (3.08 eV) and ZIF-8 (4.9 eV). XPS analysis verifies the electron donation from ZIF-8 to TiO2. Adsorptions of MO and MB differ depending on the affinities of MO or MB's functional groups on the TiO2@ZIF-8 and humidified hybrids. TiO2@ZIF-8 demonstrates 98.7% MO and 89.5% MB degradations within 100 min irradiation. Dark adsorption studies follow Langmuir model with Langmuir constants of KL = 0.445 L mg-1 for MO in the presence of TiO2@ZIF-8 and KL = 0.409 L mg-1 for MB in the presence of TiO2@ZIF-8 (84% RH). Meanwhile, pseudo-second-order kinetic model is applicable for dark experiments with rate constants of k2 = 0.918 g mg-1 min-1 for MO in the existence of TiO2@ZIF-8 and k2 = 0.917 g mg-1 min-1 for MB in the existence of TiO2@ZIF-8 (84% RH). Under irradiation, TiO2@ZIF-8 (84% RH) has higher first-order rate constant 'k' values for both MO (0.0134 min-1) and MB (0.0146 min-1) relative to that of TiO2@ZIF-8 (0.0129 min-1 for MO and 0.0112 min-1 for MB). Based on Langmuir-Hinshelwood model, TiO2@ZIF-8 (84% RH)) shows the highest adsorption coefficients (K) of 0.164 L mg-1 for MO and 0.192 L mg-1 for MB and rate constants (k) of 0.197 mg L-1 min-1 for MO and 0.182 mg L-1 min-1 for MB. Notably, the hybrids maintain high stability and photocatalytic efficiency after four consecutive degradation cycles, highlighting their potential for sustainable environmental remediation.