Use of prussian blue modified vermiculite magnetic nanoparticles in cesium adsorption

In the current study, since 137Cs has a long half-life of 30 years and should be removed from the environment in which it is located, also as it is known that the adsorption method is an advantageous method for removing metal ions from solutions on an industrial and scientific scale, the vermiculite mineral extracted by local mining procedures from the Karakoc mine in the Sivas-Yildizeli region in Turkey and the prussian blue molecule were synthesized in an environment containing Fe3O4 nanoparticles and used as a Cs adsorbent. This study mainly consists of 3 parts. In the first part, the structure characterization of the vermiculite mineral extracted by local mining procedures from the Karakoç mine in the Sivas-Yıldızeli region in our country was performed using FT-IR, XRF and XRD characterization methods, functional groups in the structure of the mineral, compounds of different types and the crystal lattice of the mineral were illuminated, experiments were conducted to determine the optimal conditions for Cs adsorption using vermiculite mineral. In the second part, a new generation PB/Fe3O4/VER nanocomposite was synthesized for the first time in the scientific literature in the presence of magnetite (Fe3O4) nanoparticles using the hydrothermal synthesis method as a result of the modification of the prussian blue molecule with the vermiculite mineral found in our country. With the VSM analysis performed, it was observed that the magnetization value of the nanocomposite was low. In the third part, a new generation PB/Fe3O4/VER nanocomposite was obtained in an alkaline environment by applying the precipitation synthesis method, which is an alternative synthesis method, in order to increase the saturation magnetization value of the nanocomposite obtained by hydrothermal synthesis, and to make comparisons. As a result of FT-IR, XRD, SEM-EDX and VSM analyses, it has been seen that a new generation of nanocomposites obtained by hydrothermal and precipitation methods have been successfully synthesized. In addition, it has been observed that the saturation magnetization value of the nanocomposite obtained by precipitation synthesis is increased by about 140 times compared to that obtained by hydrothermal synthesis. In the optimization studies conducted in the Cs adsorption process, the optimal conditions for raw vermiculite were found to be; the amount of adsorbent was 0.2 g, the pH of the solution was 8, the initial concentration of Cs was 200 mg/L, the shaking time was 5 hours and the temperature was 25°C. The optimum solution pH and the optimum initial concentration of Cs for the PB/Fe3O4/VER nanocomposite obtained by hydrothermal synthesis were determined as pH 5 and 200 mg/L, respectively. The amount of nanoadsorbent, optimum solution pH, optimum Cs initial concentration, optimum agitation time and optimum temperature were found to be 0.5 g, pH 6, 100 mg/L, 1 hour and 40°C respectively in the optimization studies for the PB/Fe3O4/VER nanocomposite obtained by precipitation synthesis. Accordingly, under optimal conditions, the Cs+ ions in the environment were able to adsorb crude vermiculite with 87%, nanocomposite obtained by hydrothermal synthesis method with 83%, and nanocomposite obtained by precipitation synthesis method with 91% efficiency, respectively. Therefore, it has been found that the nanocomposite obtained by precipitation synthesis has the ability to adsorb Cs with a higher efficiency compared to the nanocomposite obtained by crude vermiculite and hydrothermal synthesis. In the studies conducted to determine the physicochemical and thermodynamic character of adsorption, to elucidate the adsorption kinetics, it was found that the process for raw vermiculite is compatible with the Langmuir, Freundlich, D-R and Temkin isotherms, so the adsorption has both a physical and chemical character. The adsorption energy obtained as a result of the D-R isotherm is 16.23 kJ/mol, indicating that chemical adsorption dominates the adsorption process. Also, it was observed that the adsorption fit the pseudo second order kinetic model. It was concluded that the adsorption process is spontaneous and exothermic, and in addition, disorder between the liquid and solid phase increases during the adsorption of Cs on the vermiculite surface. In desorption studies performed with different types of elution solutions, it was observed that oxalic acid can desorp 90%-100% of Cs+ ions at 45°C and 65°C. In foreign ion studies, Cs adsorption could be performed with 65% efficiency in the presence of Cs+ ions at 2 times the concentration of K+ ions in solution medium. In studies with the nanocomposite obtained by hydrothermal synthesis, it was seen that the Cs adsorption process was compatible with all Langmuir, Freundlich and D-R isotherms, so there is both a chemical and physical adsorption in the process. The adsorption energy obtained as a result of D-R isotherm was found to be 10 kJ/mol. In studies with the nanocomposite obtained by precipitation synthesis, it was concluded that the Cs adsorption process was compatible with Freundlich and D-R isotherm, therefore, a physical adsorption dominates the process, the adsorption energy obtained as a result of D-R isotherm is 0.92 kJ/mol confirmed this result. According to kinetic studies it was observed that the adsorption process was compatible with the pseudo second order kinetic model. Thermodynamic studies show that the process can occur spontaneously without the need for external energy, is exothermic in character, and the disorder between the two phases increases in adsorption. In desorption studies with elution solutions, it was found that the reuptake efficiencies were quite low, and Cs adsorption can be performed with efficiencies above 90% even in the presence of K+ ions at 4 times the concentration of Cs+ ions in the solution medium under the influence of foreign ions.