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    Adsorption of Methylene Blue from Aqueous Solution Using Spent Coffee/Chitosan Composite
    (Pleiades Publishing Inc, 2023) Ozudogru, Yeliz; Tekne, Ecem
    This study aimed to investigate the adsorption of Methylene Blue from aqueous solution using different concentrations of spent coffee/chitosan composite. Adsorption parameters such as pH, contact time, initial Methylene Blue concentration, and temperature were investigated. Characterization of the adsorbent was performed with Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX). The FTIR findings showed that the hydrogen bond is a predominant contributor to the adsorption of MB by absorbed. The equilibrium data were analyzed with Langmuir and Freundlich isotherms, and kinetic models were also applied. The maximum adsorption capacity was noted to increase with an increase in temperature, from 298 to 308 K, but then decreased from 308 to 318 K. The highest maximum adsorption capacities among all coffee/chitosan beds were 75.76 mg g(-1) at 298 K, 108.7 mg g(-1) at 308 K, and 33.67 mg g(-1) at 318 K. These results show that a waste coffee/chitosan composite is a cost-effective, eco-friendly material for removing methylene blue from aqueous solution.
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    Adsorption of U(VI) and Th(IV) ions removal from aqueous solutions by pretreatment with Cystoseira barbata
    (Springer, 2020) Ozudogru, Yeliz; Merdivan, Melek
    Radioactive wastes from human activities can spread to the environment and pose a serious threat to human health. This paper examined the removal of radioactive U(VI) and Th(IV) ions from aqueous solutions by a modified alga, Cystoseira barbata (Stackhouse) C. Agardh. The effects of pH, contact time, radioactive ion concentration, and temperature were examined on the adsorption and desorption of the radioactive ions by the algae from different solutions. The maximum adsorption capacity (q(ma)x) value was 217.39 mg g(-1) at 45 degrees C for U(VI) and 305.81 mg g(-1) at 45 degrees C for Th(IV). The data were analyzed with Langmuir and Freundlich isotherms. Scanning electron microscopy and Fourier transform infrared spectroscopy analyses were performed to determine the changes on the surfaces of the algae following adhesion of radioactive ions to the algal surfaces. The success rate for recovery of the loaded radioactive materials was more than 90%.
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    BIOSORPTION OF Cu(II) AND Pb(II) IONS USING MARINE BROWN ALGAE Padina pavonica
    (Parlar Scientific Publications (P S P), 2013) Ozudogru, Yeliz
    In this study, the removal of Cu(II) and Pb(II) ions from aqueous solutions using the brown algae Padina pavonica J.V. Lamouroux 1816 was studied, and the effects of solution pH, the contact time, and the initial metal concentration on biosorption were investigated. The pH affected the biosorption capacity, and optimum pH value was 6 for both ions, and the sorption process reached equilibrium in 30 min. The application of Freundlich and Langmuir isotherm models showed that the type of adsorption (physical and chemical) changed, depending on the selected metal. According to recovery studies, the best eluents were 0.1 M HCl for the Cu(II) ions and 0.1 M HNO3 for the Pb(II) ions. Therefore, the removal of Pb(II) was more efficient than that of Cu(II) when P. pavonica was used as a biosorbent.
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    Effect of sodium acetate and sodium nitrate on biochemical composition of green algae Ulva rigida
    (Springer, 2015) Ak, Ilknur; Oztaskent, Cenk; Ozudogru, Yeliz; Goksan, Tolga
    In this study, the effect of sodium acetate (C2H3NaO2) and sodium nitrate (NaNO3) concentrations on proximate and fatty acid composition of Ulva rigida (C. Agardh) was studied. Two trials were carried out. In the first experiment, the C2H3NaO2 was used as an organic carbon sources and five different concentrations of C2H3NaO2 were added; 0.25, 0.5, 1, 2, and 3 g/l. In the second trial, at the beginning of the experiment, 1 g/l C2H3NaO2 was added all groups, but the nitrogen regimes of the groups were changed. Five different nitrogen concentrations were used; 0.2 g/(l d), 0.3 g/(l d), 0.4 g/(l d), 0.6 g/(l d), and 0.11 g/(l d). According to our results, U. rigida cultivated with C2H3NaO2 and NaNO3 can successfully be used for both animal and human nutrition. The fatty acid methyl esters results showed that fatty acid contents of U. rigida were influenced by carbon (C2H3NaO2) and nitrogen (NaNO3) concentrations. The saturated fatty acids levels of U. rigida cultured in different NaNO3 concentrations were very high. The results indicated that C2H3NaO2 and NaNO3 addition during the culturing had considerable affects on proximate and fatty acid composition of the U. rigida. Using both C2H3NaO2 and NaNO3 offers a balanced fatty acid composition for both animal and human nutrition.
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    Removal of malachite green dye by adsorption onto chitosan-montmorillonite nanocomposite: Kinetic, thermodynamic and equilibrium studies
    (Wiley-V C H Verlag Gmbh, 2025) Cetin, Mert; Ozudogru, Yeliz
    In this study, the efficiencies of chitosan, montmorillonite, and chitosan/montmorillonite composites in various ratios for the removal of malachite green dye from aqueous solutions were investigated, and their maximum adsorption capacities were compared, and the effects of factors such as composite concentration, pH, contact time, dye concentration, and temperature were examined. Recovery attempts using different chemicals were also performed. Adsorption was analyzed using Langmuir and Freundlich isotherm models, and thermodynamic analyses were conducted. Fourier-transform infrared (FTIR) and scanning electron microscopy (SEM) analyses were used to investigate surface changes. The highest adsorption capacity was found for the 20% chitosan/montmorillonite composite (400 mg g-1). Temperature studies indicated a decrease in adsorption capacity with increasing temperature. Kinetic studies observed that the data fit the pseudo-second-order kinetic model better. In recovery attempts, more than 95% recovery was achieved with HNO3 and HCl. FTIR results showed that chitosan-montmorillonite interactions involved -NH, -OH, C=O, and C-O bonds, while dye binding was mainly through OH bonds. SEM analysis revealed that montmorillonite reduced surface cracks and roughness, creating a more homogeneous structure, and more rough areas appeared after dye binding. As a result, the chitosan/montmorillonite composite significantly enhanced dye adsorption capacity.
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    Removal of methylene blue from aqueous solutions by brown alga Cystoseira barbata
    (Desalination Publ, 2017) Ozudogru, Yeliz; Merdivan, Melek; Goksan, Tolga
    The removal of dyes from wastewater is crucial and considered an environmental challenge. Biosorption is an alternative technology to conventional processes aiming at the removal of toxic metals and dyes from polluted waters. In this study, Cystoseira barbata (Stackhouse) C. Agardh was used to remove the methylene blue (MB) from aqueous solution. The effects of solution pH, contact time and initial MB concentration at different temperatures were investigated. The adsorption reached to equilibrium in 25 min and the pH did not have an important role on the biosorption. The Freundlich isotherm model showed slightly stronger correlation than Langmuir isotherm model especially at 25 degrees C. The maximum adsorption capacity (q(m)) increased in parallel to the rise of temperature and reached to 14.97 mg/g at 45 degrees C. C. barbata can be successfully used for the removal of MB from aqueous solution.