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    Comparative Investigation of Phosphate Adsorption Efficiencies of MOF-76 (Ce) and Metal Oxides Derived from MOF-76 (Ce)
    (Amer Chemical Soc, 2024) Cavusoglu, Ferda Civan; Ozcelik, Gulsum; Bayazit, Sahika Sena
    Phosphate pollution is a very challenging problem for the water environment. Phosphate mixed with water in various ways causes eutrophication. To sustain life in aquatic systems, phosphate ions must be cleaned. Therefore, it is very important to remove phosphate in wastewater. Here, an adsorption method has been tried for the removal of phosphate. MOF-76 (Ce), a cerium-based metal-organic framework, was synthesized by a hydrothermal method. Since metal oxides are known to be successful in phosphate adsorption, CeO2 nanoparticles were also obtained by pyrolysis of this MOF structure. The phosphate adsorption efficiencies of both adsorbents were compared. The characterization methods (SEM, FTIR, XRD, and TGA) were applied to adsorbents. The kinetic, isotherm, and thermodynamics studies were applied to experimental results. At 298 K, the adsorption capacity of MOF-76 (Ce) is higher than that of CeO2, according to Langmuir isotherm q(m) values. The q(m) values are 72.97 and 55.71 mg/g, respectively. Both adsorbents follow the pseudo second-order kinetic model. It has been found that MOF-76 (Ce) has a pH-selective property in phosphate adsorption. No change was observed in the phosphate adsorption capacity of CeO2 with pH. In terms of thermodynamics, the endothermic reaction is valid for both adsorbents.
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    Enhanced & effective phosphate recovery from water by indium fumarate & zirconium fumarate metal-organic frameworks: Synthesis, characterization, adsorption, kinetic and isotherm studies
    (Elsevier, 2022) Ozcelik, Gulsum; Cavusoglu, Ferda Civan; Ozkara-Aydinoglu, Seyma; Bayazit, Sahika Sena
    Eutrophication has been an important environmental issue for the last decade. Agricultural and industrial actions cause high concentrations of phosphate discharging to surface and ground waters, and high levels of phosphate concentration causes eutrophication. The decreasing of the phosphate concentration is an essential matter and adsorption is one of the most effective solutions for this purpose. In this study, indium fumarate (In-fum) and zirconium fumarate (Zr-fum) were prepared. Surface characterizations of these adsorbents were applied by XRD, FTIR, SEM, TGA, DSC, and BET surface analysis. The surface areas of In-fum and Zr-fum were determined as 181.19 m(2)/g and 527.96 m(2)/g, respectively. Water absorption abilities of adsorbents were tested by Karl-Fischer method. The water contents inside the pores of water-treated Zr-fum and In-fum are 0.0560% (w/w) and 0.0694% (w/w), respectively. Phosphate adsorption performances of In-fum and Zr-fum particles were studied by parametric research, investigating the effects of adsorbent quantity, contact time, solution pH, initial solution concentration, adsorption temperature, and co-existing ions. The phosphate adsorption uptake (q(e)) of Zr-fum is 33.52 mg/g and qe value of In-fum is 31.29 mg/g when adsorbent quantity is 1 mg. The kinetic studies reveal that both adsorbents follow pseudo second-order kinetic model according to the R-2 values. These values are 0.93 for In-fum and 0.98 for Zr-fum. The rate constants are 0.15 g/mg min (In-fum) and 0.14 x 10(-2) g/mg min (Zr-fum). Theoretical maximum phosphate adsorption uptake (q(m)) of In-fum is 93.40 mg/g at 318 K. The q(m) value of Zr-fum is 67.44 mg/g at 308 K. Phosphate adsorption over In-fum is strongly dependent on temperature change whereas the effect of temperature on adsorption performance of Zr-fum is insignificant. The pH of the phosphate solution should be below 7 to obtain an appropriate surface and phosphate ion charge combination. The presence of co-existing chloride ions does not dramatically affect phosphate adsorption capacity.
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    Gliclazide Removal Efficiency of Carbon-Based Magnetic Materials: Isotherm and Kinetic Studies
    (Wiley-V C H Verlag Gmbh, 2022) Cavusoglu, Ferda Civan
    Gliclazide, one of the micropollutants that can be detected in water, is widely used in the treatment of type II diabetes patients. In this study, the removal of gliclazide from aqueous solutions with magnetic carbon-based materials was investigated. Magnetic activated carbon (MAC) and magnetic multiwalled carbon nanotube (MMWCNT) adsorbents were prepared and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis methods. The effects of various parameters affecting the adsorption process were examined. The adsorption systems were compatible with the Langmuir isotherm model and the pseudo-second-order kinetic model. The maximum monolayer adsorption capacities of the MAC adsorbent (298 K) and the MMWCNT (308 K) were 109.20 and 71.59 mg g(-1), respectively. According to desorption studies, adsorbents could be regenerated by around 70 % in 6 hours.
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    Magnetic carbon composites as regenerable and fully recoverable adsorbents: Performance on the removal of antidiabetic agent metformin hydrochloride
    (Elsevier, 2021) Cavusoglu, Ferda Civan; Bayazit, Sahika Sena; Secula, Marius Sebastian; Cagnon, Benoit
    The present work describes three newly-prepared magnetic-carbon composites (M-CCs) applied as adsorbents. The M-CCs were prepared by the co-precipitation method, grafting Fe(II) and Fe(III) oxides onto the surface of different matrices: PAC, GNP and MWCNT in order to achieve M-PAC, M-GNP and M-MWCNT, respectively. The composites were characterized by Fourier Transform Infrared spectroscopy, X-ray Diffraction Spectroscopy. Scanning Electron Microscopy was used for characterization of M-MWCNTs, Transmission Electron Microscopy was used for characterization of M-GNP composites. Thermogravimetric analyses were performed for each of the three M-CCs. It is found that about 70% of M-CCs consist in Fe3O4 nanoparticles. M-CCs adsorption features and performance towards the removal of a pollutant model from aqueous solutions was established. They were tested for Metformin hydrochloride adsorption, a worldwide antidiabetic pharmaceutical agent. The parameters of adsorbent dose, adsorption duration, initial concentration of adsorbate solution, temperature, pH and co-existing ion concentration were considered as adsorption independent variables. The kinetic tests show that the Pseudo second order kinetic model (PSO) fit best the three-adsorption systems. M-GNP is the fastest adsorbent of the three (k(2) = 0.36 g/mg min). The three investigated adsorption systems obey the Langmuir isotherm model. Pinpointing M-GNP (q(m) = 8.83 mg/g) as the most efficient adsorbent in normal conditions, and M-MWCNT (q(m) = 26.17 mg/g at 318 K) at higher values of temperature. Acid conditions favor adsorption of Metformin hydrochloride onto M-MWCNT, alkaline for M-PAC, whereas M-GNP provides best performance under amphoteric conditions. Coexisting ions affected Metformin hydrochloride adsorption only in case of M-MWCNT and M-GNP. Desorption tests were also carried out by using phosphate buffer solution. M-GNP provides best desorption ratios, reaching nearly 66% of Metformin hydrochloride desorption after each use. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
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    Preparation of magnetic activated carbon-chitosan nanocomposite for crystal violet adsorption
    (Korean Institute Chemical Engineers, 2019) Cavusoglu, Ferda Civan; Akan, Seher; Ari, Ezgi Aleyna; Cetinkaya, Ezgi; Colak, Elif; Dastan, Gamze Nur; Deniz, Semina
    Magnetic, cheap and versatile adsorbents were developed for crystal violet (CV) adsorption in this study. These adsorbents are magnetic activated carbon (AC-Fe3O4) and chitosan grafted magnetic activated carbon (Chitosan-AC-Fe3O4). Fe3O4 and chitosan were also used for adsorption. X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), zeta potential analysis and Fourier transform infrared spectroscopy (FTIR) methods were used for characterization of adsorbents. Adsorption parameters for CV were investigated. Raw chitosan and Fe3O4 were also used for CV adsorption to compare the results of composites. The chosen adsorption parameters are amount of adsorbent, contact time, initial CV concentration, and temperature. The equilibrium period was observed to be very short for chitosan and Fe3O4 nanoparticles. The adsorption efficiencies of these adsorbents are very low. AC-Fe3O4 and AC-Fe3O4-Chitosan nanoparticles reached equilibrium at 80 min. The all adsorbent-CV systems followed pseudo second-order kinetic model. AC-Fe3O4 and AC-Fe3O4-Chitosan composites suited non-linear Freundlich isotherm for all temperatures (298, 308 and 318 K). Regeneration of adsorbents was also investigated. 1 M of acetic acid and 0.1 M of NaOH solutions were tested. Acetic acid solution desorbed CV better than NaOH solution at 6 hours.
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    Removal of crystal violet dye from aqueous solutions using montmorillonite-based nanoclays: Kinetic and equilibrium studies
    (Gazi Univ, Fac Engineering Architecture, 2023) Cavusoglu, Ferda Civan; Bayazit, Sahika Sena; Salam, Mohamed Abdel
    In recent years, water pollution has become a major problem, especially due to the wastes discharged from different sectors without treatment. Among these, there are various paint wastes used by the textile, leather, paper and cosmetics sectors. Crystal violet (CV) is a widely known cationic dye and is often used as a colorant in industries. CV dye is known to be toxic to humans and animals at 1 ppb. For this reason, it is very important for environmental safety to treat industrial wastewater from crystal violet before discharge. This research aimed to evaluate the efficacy of two different montmorillonite-based nanoclays (B1 and B2) as a low-cost material for the removal of crystal violet dye from aqueous solutions. Structural characterizations of nanoclays were analyzed using FTIR and TGA methods. All parameters that could affect the CV adsorption process were optimized in a batch system. The effects of various factors (adsorbent dose, contact time, solution pH, co-existing ion effects, adsorption temperature, initial dye concentration) on the adsorption process were investigated. Experiments to investigate the mechanism of the CV-nanoclay adsorption system showed that the adsorption kinetics and equilibrium parameters fit better with the Pseudo second-order kinetic model and the Langmuir isotherm model, respectively. The maximum adsorption capacities (qm) of B1 and B2 adsorbents were obtained as 224.63 mg/g at 25 degrees C and 360.30 mg/g at 45 degrees C, respectively. A suitable combination of surface and CV ion charge was obtained at low pH values (<= 7) of the CV solution. The presence of co-existing NaCl ions did not significantly affect the CV adsorption capacity. When the results were evaluated, it was seen that the montmorillonite-based adsorbents were effective and cost-effective adsorbents for CV dye removal.
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    Removal of toxic Cr(VI) from aqueous medium with effective magnetic carbon-based nanocomposites
    (Tubitak Scientific & Technological Research Council Turkey, 2023) Cavusoglu, Ferda Civan; Ozcelik, Gulsum; Bayazit, Sahika Sena
    Cr(VI), which has toxic effects, is a heavy metal and it must be removed from the environment due to the various damages it causes. In this study, the removal of Cr(VI) pollutants from aqueous solutions with Fe3O4-based materials using a batch adsorption technique was investigated. Magnetically modified graphene nanoplatelet (GNP)-based nanocomposites were prepared and their structures were characterized by FTIR, XRD, SEM, BET, and TGA techniques. The effects of various physicochemical parameters such as adsorbent dose, contact time, initial Cr(VI) solution concentration, pH, and the presence of coexisting ions (NaCl) on the adsorption process were investigated. Accordingly, the optimum conditions for Cr(VI) removal were determined. Nonlinear Langmuir, Freundlich, and Temkin isotherm models and pseudo-first-order, pseudo-second-order, and Bangham kinetic models were used to investigate the adsorption mechanism. The experimental data relatively fit the second-order kinetic model and the Freundlich isotherm model. The maximum adsorption capacities for pure Fe3O4 (Fe:GNP 1:0), Fe:GNP (2:1), and Fe:GNP (1:1) nanocomposite materials at 298 K and pH of approximately 5 were obtained as 12.71 mg/g, 27.03 mg/g, and 62.27 mg/g, respectively. This result showed that Cr(VI) removal increased as the amount of GNP in the composite material increased. Generally, the results confirmed that magnetically modified GNP based adsorbents are functional and promising materials that can be used for the removal of pollutants such as Cr(VI) from aqueous media.
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    Synthesis of PET-based urethane-modified alkyd resins from depolymerization intermediates of post-consumer PET bottles: coating properties and thermal behaviors
    (Springer, 2023) Cavusoglu, Ferda Civan; Acar, Isil
    Urethane-modified alkyd resins were synthesized using the depolymerization intermediates obtained from simultaneous hydrolysis-glycolysis reactions of post-consumer poly(ethylene terephthalate) (PET) bottles with dipropylene glycol (DPG) and water. For this aim, first, the synthesis of a four-component reference alkyd resin having an oil content of 50% was synthesized by using tall oil fatty acid (TOFA), trimethylolpropane (TMP), phthalic anhydride (PA), and dipropylene glycol (DPG). The PET-based alkyd resins were also synthesized using different amounts and types of purified and fractionated depolymerization intermediates (water-insoluble fraction, WIF, and water-soluble and crystallizable fraction, WSCF) under the same reaction conditions. For the synthesis of PET-based alkyd resins, the depolymerization intermediates were used partially or completely instead of dibasic acid and/or diol components in alkyd resin formulations. In order to determine the optimum modification ratio for urethane-modified alkyd resin synthesis, the reference alkyd resin was reacted with toluene diisocyanate (TDI) at different molar ratios (NCO/OH: 1/1, 1/2, and 1/3), and the optimum NCO/OH ratio was determined as 1/1, according to the surface coating properties. And, then, all PET-based urethane-modified alkyd resins were prepared by the modification reactions of the PET-based alkyd resins with TDI at an optimum ratio. At the end of the study, it was observed that the use of waste PET intermediates (WIF or WSCF) did not cause any negative effects on physical/chemical surface coating and thermal properties; on the contrary, some properties were obtained as superior than that of the reference resin. In conclusion, it seems possible to use PET-based urethane-modified alkyd resin could be used as a cheap, environmentally friendly, and relatively economic binder component in synthetic paint formulations. In the synthesis of urethane-modified alkyd resin, using a certain amount of waste PET intermediate instead of dibasic acid and/or diol component will reduce raw material costs and also benefit the environment by re-evaluation of recycled PET. Thus, it could be both possible to recycle of post-consumer PET bottles, which are a valuable waste, and to provide cheap raw materials without compromising its features for paint formulations. These results are remarkable in terms of sustainability and waste management besides are also important for the economy and paint industry.