B. Buyuk

Selenium Adsorption on Activated Carbon by Using Radiotracer Technique

Selenium (Se) is an essential trace element for human beings and plays important roles in human health but it is also toxic at concentrations above 1 mg of selenium per kg of body weight. Therefore, elimination of selenium ions from aqueous solutions is important. Se can be eliminated by using activated carbon as an adsorbent. Radiotracer concept is applicable for observation of elimination mechanism. For this reason, selenium radioisotope can be used as tracer. Selenium dioxide is irradiated in the central thimble of ITU TRIGA Mark II Training and Research Reactor for radiotracer production. Radioactivity measurements are carried out by the gamma-ray spectroscopy system to determine the effect of different experimental parameters. The relative importance of test parameters like concentration of adsorbate, pH of the solution, and contact time on adsorption performance of activated carbon for selenium ion is examined. Typical adsorption isotherms (Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin) are determined for the mechanism of sorption process. Evaluation of experiments for different parameters shows possibility of elimination of selenium from aqueous media by using activated carbon.

Evaluation of Rubidium and Potassium Diffusion in Soil by Radiotracer Technique

In this study, diffusion of rubidium and potassium in soil was observed representing two alkaline elements. Generally, these elements are found as salt compounds in the earth. Soil columns were prepared in the laboratory conditions. Rubidium chlorite and potassium nitrate compounds were irradiated at ITU TRIGA Mark II nuclear research reactor at the Energy Institute of ITU to produce the radiotracer 86Rb and 42K. The irradiated compounds were sprinkled to the surface of different soil columns and were watered with realistic amounts. Radioactivity measurements were carried out by using a scintillation detector at the outside of the column for different soil depths in different diffusion times. As the results of the study, the behavior of two alkaline elements was observed appropriately similar in the soil.

Investigation of Salt Diffusion in Soil by Using Radiotracing Technique

In this study, it is aimed to observe diffusion of sodium in soil samples by using radiotracing technique. To produce the radiotracer 24Na, sodium-carbonate compound was irradiated at ITU TRIGA Mark II Research reactor at Energy Institute of Istanbul Technical University. The irradiated sodium-carbonate samples were sprinkled to the surface of soil columns. Then soil was watered with representative amounts of water according to selected rain regimes in Istanbul. Radioactivity measurements were carried out by using high efficiency gamma-ray measurement system at the outside of the column for different soil depths in different times.

Evaluation for elimination of methylene-orange from aqueous media by using membrane

Elimination of the methylene orange which are the main sources of environmental pollution from aqueous media were investigated experimentally by using 0.45 µm hydrophilic nylon membran. Removal of the methylene orange were performed with successfully. Furthermore, repetition effect also was examined rationally. With this study, membrane usage for elimination of the methylene orange are convenient for elimination of them from the aqueous media.

Gamma and Neutron Shielding Behavior of Spark Plasma Sintered Boron Carbide-Tungsten Based Composites

In this study gamma and neutron attenuation properties of boron carbide-tungsten (B4C-W) based composites were investigated. B4C-W based composites were produced by spark plasma sintering (SPS) method. W additions were 5%, 10%, and 15% by volume. Samples with theoretical densities were obtained. Occurance of W2B5 phase with a reaction between B4C and W particles were observed with XRD and SEM investigations. The materials were subjected to gamma and neutron sources. Cs-137 and Co-60 gamma radioisotopes were used as gamma, and Pu-Be Neutron Howitzer was used as neutron source. Linear and mass attenuation coefficients of the composites were carried out for gamma sources by using gamma transmission technique. Furthermore, total macroscopic cross-sections of the samples were determined for Pu-Be neutrons. In conclusion, increasing W ratio in the B4C-W system causes higher gamma attenuation behavior for gamma sources, but the macroscopic cross-sections of the B4C-W composites decrease by increasing W concentration.

Assessment of Adsorption Parameter Effectiveness for Radio-Selenium and Radio-Iodine Adsorption on Activated Carbon

Selenium and iodine are found in human body and primarily used in nutrition, and excess or absence of them can lead to diseases. Therefore, their possible dispersion to environment through mining and reprocessing of metals, combustion of coal and fossil fuel, nuclear accidents, or similar activities needs remediation. Adsorption is one of the useful techniques to remove pollutants. In this study, a factorial design is used to determine the effect of pH, concentration of adsorbate, and contact time upon adsorption. Adsorption capacities of radio-selenium and radio-iodine were evaluated for factorial design using activated carbons. The used activated carbon samples were prepared by chemical and physical activation methods. Radioactivity measurements were carried out by using high-resolution gamma spectroscopy system. Results of the research lead to provide useful information about energy generation and management processes by preventing hazardous elements’ dispersion to the environment.