ABSTRACT
In the present study, an Iranian natural zeolite (Sabzevar region) was evaluated as a natural adsorbent for the elimination and immobilization of strontium ions from an aqueous solution. For improving the adsorption efficiency of strontium ion, the zeolite surface was modified by the Schiff base ligand of bis (2-hydroxybenzaldehyde)1,2-diaminoethane (H2L). The natural zeolite and zeolite/H2L were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray fluorescence (XRF), BET and scanning electron microscope (SEM). Analysis of the natural zeolite showed that the zeolite is from the type of clinoptilolite and has a crystalline structure with the specific surface area 29.74 m2/g. The results showed that strontium adsorption onto modified zeolite increases compared to unmodified zeolite from 64.5% to 97.2% (at pH = 6). The effective parameters pH, adsorbent dosage, initial concentration of strontium ions, contact time, temperature, and interfering ions, were studied and optimized. The maximum adsorption efficiency was confirmed by modified zeolite and found to be 97.5% after 60 min of equilibrium time at pH 6, 0.05g as adsorbent dosage, and at 25 °C. Adsorption of strontium was confirmed by Langmuir model with maximum adsorption capacity of 10.31 mg/g. Kinetic studies showed that the adsorption of strontium ions on the adsorbent follows pseudo-second-order (PSO) model. Also, the thermodynamics of the adsorption process indicated that the adsorption of strontium on zeolite/H2L is an endothermic and spontaneous process, and the adsorption mechanism is a combination of physical and chemical adsorption. Finally, to manage the secondary waste generated from the adsorption process, strontium ions were immobilized in a zeolite structure. The results showed that the stabilization is well done with the thermal preparation process. After thermal treatment at 25-900 °C, modified zeolite satisfactorily retains strontium during back-exchange tests with NaCl solution. According to the results, the amount of strontium released from the adsorbent phase decreases from 52.6 to 1.6% with increasing heat treatment temperature.
ABSTRACT
A MnO2-ZrO2-polyacrylonitrile (MnO2-ZrO2-PAN) composite ion exchanger was produced and its properties were examined by Fourier-transformed infrared spectroscopy, scanning electron microscopy, The BET (Brunauer, Emmett and Teller) surface area, X-Ray diffraction analysis and thermogravimetric analysis. The adsorption of Strontium (Sr) from solutions by MnO2-ZrO2-PAN composite was studied thru batch experiments. The distribution Coefficient of Sr (II) on the composite sorbent was investigated against pH, interaction time, and primary concentration ion. To study the kinetics of adsorption, Pseudo-first-order and Pseudo second-order adsorption kinetics were studied and the results revealed that adsorption kinetics better fit to the pseudo-second-order model. Three iso-temperature models, Langmuir, Freundlich, and Temkin were applied to fit the experimental results. Among those models, Langmuir revealed the most suitable one with minimum deviation. The created composite exhibited strong compatibility to the elimination of Y (III), Ni (II), Pb (II), and Co (II) from radioactive waste streams. On the other, it is evident from the data that the quantifiable extraction of Sr (II) ions from Zr (IV), Mo (VI), and La (III) is feasible. MnO2-ZrO2 Loaded with (PAN) Polymer was figured out to have high ion exchange capacity and thermal stability and selectivity for strontium.
ABSTRACT
CONTEXT: Nowadays, radionuclides with high ß- particle energies such as (166)Ho are recommended for bone marrow ablation in patients with multiple myeloma. The addition of skeletal targeted radiotherapy to the patients can improve the response rate in phase I and II trials, with promising long-term survival data. AIMS: In this work, the absorbed dose to each organ of human for (166)Ho-propylene di-amino tetra methy1enephosphonicacid (PDTMP) was evaluated based on biodistribution studies in rats and was compared with (166)Ho-tetraazacyclododecane tetramethylene-phosphonate (DOTMP) as the only clinically used Ho-166 bone marrow ablative agent. SETTINGS AND DESIGN: In this work, the accumulated activity in animals was extrapolated to the accumulated activity in humans by mass extrapolation method. The absorbed dose to each organ of human for (166)Ho-PDTMP was evaluated by medical internal radiation dose method. MATERIALS AND METHODS: In this study, 166 Ho-PDTMP complex was prepared successfully using an in-house synthesized PDTMP ligand and (166)HoCl 3. Radiochemical purity of (166)Ho-PDTMP was checked by instant thin layer chromatography (>99%). The biodistribution of (166)Ho-PDTMP in wild-type rats was checked in animal tissues up to 48 h. STATISTICAL ANALYSIS USED: All values were expressed as mean ± standard deviation, and the data were compared using Student's t-test. Statistical significance was defined as P < 0.05. RESULTS: The highest absorbed dose for this complex is observed in red marrow with 0.691 mSv/MBq. (166)Ho-PDTMP demonstrated a higher red marrow: Non target organ uptake ratio compared to (166)Ho-DOTMP. CONCLUSIONS: The results showed that 166 Ho-PDTMP has considerable characteristics compared to (166)Ho-DOTMP and therefore can be a good candidate for bone marrow ablation.
