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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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    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.