Berkan Çetinkaya

Factors Affecting Lanthanum and Cerium Biosorption on Pinus brutia Leaf Powder

The biosorption behavior of lanthanum and cerium ions from aqueous solution by leaf powder of Pinus brutia was separately studied in a batch system as a function of initial pH, contact time, initial metal ion concentration, temperature, and adsorbent amount. The uptake of lanthanum and cerium was increased when the initial pH of the solution was increased. Thermodynamic parameters such as standard enthalpy (ΔH°), entropy (ΔS°) and free energy (ΔG°) were calculated and the results indicated that biosorption was endothermic and spontaneous in nature. The biosorption of lanthanum and cerium on powdered leaf of Pinus brutia was investigated by the Freundlich, Langmuir, and D-R isotherms. The results show that lanthanum and cerium adsorption can be explained by the Langmuir isotherm model and monolayer capacity was found as 22.94 mg g−1 for lanthanum and 17.24 mg g−1 for cerium. Desorption of lanthanum and cerium was studied using 0.5 M HNO3 solution. The results suggested that powdered leaf of Pinus brutia may find promising applications for the recovery of lanthanum and cerium from aqueous effluents.

Investigation of strontium sorption onto Kula volcanics using Central Composite Design

In performance assessment studies, the uptake of the radioactive elements by rock formations play an important role in retarding their aqueous phase migration. Sorption studies of radionuclides have been conducted to obtain data on the distribution coefficient (K(d)) that is as an input parameter in the performance assessment of the geological disposal of radioactive wastes. In this work, sorption experiments were studied in a batch sorption system using Sr(NO(3))(2) solution on non-treated and HCl-treated Kula volcanics. The distribution coefficient (K(d)) values of Sr(2+) derived from batch experiments were used to evaluate the migration behavior of Sr(2+). Central Composite Design was used in the experiments. Sr sorption was studied as a function of pH, temperature, initial concentration of adsorbate and contact time. The results show that the K(d) values are higher at pH 7-9 which is the pH range of the natural waters. The kinetic data conformed better to the pseudo-second-order equation. Thermodynamic parameters ΔH°, ΔS° and ΔG° were estimated and these parameters show that adsorption is endothermic. The correlation coefficients indicate that the Langmuir model fits better for the strontium sorption onto non-treated and HCl-treated Kula volcanics with monolayer capacities as 2.04 and 1.72 mg/g, respectively.

Radioiodination and preliminary biological tests of aniline-mustard and its glucuronide conjugate as a potential anticancer prodrug

Aniline-mustard and its glucuronide conjugate were radioiodinated with 131I. The preliminary dynamic tests were carried out on rabbits. The scintigrams showed clearly that the glucuronide conjugate of aniline-mustard was very quickly cleared from the metabolism, accumulating in the bladder in about 15 minutes. The clearance time of radioiodinated aniline-mustard-glucuronide was considerably longer (about 45 min.). The results obtained from the biodistributional studies have represented interesting differences between the metabolic details of radioiodinated compounds, and indicated that the glucuronide conjugate of aniline-mustard may be a promising radioiodinated prodrug, if verification of its selective accumulation in some kinds of tumor cells can be obtained.

Transfer of orally administrated iodine-131 into chicken eggs

Radioactive iodine-131 as both as free iodide (Na131I) and covalently bound to aniline (aniline-131I) was added to the drinking water of two Leghorn laying hens as a single dose and also as a cumulative dose over 1 week. The radioactivity of the principal parts of the eggs, i.e. shell, white, and yolk, was measured, and the radioactivity levels per gram material, and percent of the total radioactivity were calculated. The radioactivity measurements were continued for 1 month following the administration of 131I. In the case of the single dose administration, the results obtained showed that about 15% of the total radioactivity administered as Na131I was transported into the egg structure; compared to only about 1% for aniline-131I. After cumulative administration, about 15% of the total administered radioactivity was transported into the egg structure with both forms of 131I. This was probably because of metabolic cleavage of iodine bonds in the labeled aniline molecules during the longer period of exposure. These results also showed considerable accumulation of 131I in the egg yolks. In the case of the single dose administration, 131I can be detected in eggs up to about 20 days after administration, and up to about 30 days, in the case of the cumulative administration over 1 week.

Preparation and characterization of sol-gel derived (ThxCe1−x)O2 microspheres

Abstract (ThxCe1−x)O2 microspheres (x=0.50, 0.75 and 0.95) with high homogeneity were prepared via sol-gel technique, starting from the initial chemical materials Th(NO3)4·5H2O and (NH4)2[Ce(NO3)6]. The sols were prepared by addition of ammonia under pH and temperature control. Sols were gelated to spherical form in a gelation system consisting of peristaltic pump, flow regulator, nozzle and a glass column. To obtain crack-free spheres suitable for gelation, source sols neutralization conditions, drop formation and pre-hardening medium were investigated and the optimum conditions were determined. After aging, washing and drying steps, gel microspheres were characterized. For this purpose, thermal behaviors of spheres were investigated with TG/DTA analysis. Dried microspheres at 80°C were calcined at three different temperatures, namely 450°C, 800°C and 1150°C, and crystal parameters were calculated from XRD data. BET specific surface area and BJH porosity analyses were also carried out.