Volume 106, Issue 3

Imidazolium bis(2-ethylhexyl)phosphate ionic liquid was anchored on a polystyrene-divinylbenzene (PS-DVB) copolymer and the product (R-Im-DEHP) was studied for the extraction of Am(III) and Eu(III) from dilute nitric acid medium to examine the feasibility using the anchored adsorbent for their mutual separation. The effect of various parameters such as the duration of equilibration, concentration of nitric acid, europium ion, and diethylenetriaminepentaacetic acid (DTPA) in aqueous phase on the distribution coefficient ( K d ) of Am(III) and Eu(III) was studied. The distribution coefficient of Am(III) and Eu(III) decreased with increase in the concentration of nitric acid. Rapid extraction of metal ions in the initial stages of equilibration followed by the establishment of equilibrium occurred within 4 h. The data on the rate of uptake of Am(III) and Eu(III) were fitted into pseudo-first order and pseudo-second order rate equation. The extraction isotherm was fitted to Langmuir and Freundlich adsorption models and the apparent europium extraction capacity was determined. The mechanism of extraction was elucidated and the conditions needed for efficient separation of Am(III) from Eu(III) was optimized using DTPA. The study indicated the possibility of using R-Im-DEHP for the separation of Eu(III) from Am(III) with high separation factors.

The performance of the hollow fiber renewal liquid membrane (HFRLM) in the continuous and recycling modes for the extraction of uranium(VI) from the acidic sulfate solution has been investigated. Alamine 336 diluted in kerosene was used as a carrier in liquid membrane (LM) phase. In the batch experiments, the effects of sulfuric acid, extractant and uranium(VI) concentration were studied and the optimum concentration of the donor and LM phases were determined 0.15 mol L −1 and 0.0125 mol L −1 , respectively. Various parameters affecting the HFRLM performance including the lumen and shell side flow rate, organic/aqueous volume ratio, acceptor phase type and concentration of carrier and acceptor phase were studied. The mass transfer flux increases with increasing the lumen side flow rates and the shell side flow rate did not have any significant effect. The uranium transfer flux increases with increasing O/A ratio, acceptor and Alamine 336 concentration, and reaches a maximum value at 1/20, 0.5 mol L −1 and 0.0125 mol L −1 , respectively. Further increase in these parameters result in uranium transfer decrement. The results show that liquid membrane phase is a rate-controlling step. Among the investigated acceptor phases, 0.5 mol L −1 NH 4 Cl result in 60.35% uranium(VI) recovery in the recycling mode.

U(VI) sorption on nano-crystalline α-MnO 2 was studied in NaClO 4 medium as a function of pH by batch sorption method in presence and absence of carbonate and subsequently employing surface complexation modeling (SCM) to predict species responsible for U(VI) sorption. The kinetic study of U(VI) sorption on nano-crystalline α-MnO 2 was carried out to fix the time of equilibration. In presence of carbonate, U(VI) sorption on nano-crystalline α-MnO 2 increases with pH of the suspension, leveling off in the pH range 5–8.5 thereafter decreasing at higher pH. However, in absence of carbonate, U(VI) sorption on nano-crystalline α-MnO 2 remains close to 100% at pH>5. The difference in sorption behavior of uranium in the presence and absence of carbonate can be explained in terms of uranium speciation in the two systems. The dissolution of nano-crystalline α-MnO 2 was studied in presence and absence of carbonate to ascertain its role in sorption. Surface complexation modeling was satisfactorily able to explain the sorption phenomena in all the systems. In addition, U(VI) sorption on nano-crystalline α-MnO 2 was compared with literature data on U(VI) sorption by δ-MnO 2 .

The sorption behaviors of Ce(III), as a representative of trivalent lanthanide ions, and Te(IV), Zr(IV) and Nb(V) as fission products representatives, as well as Hf(IV), from various aqueous media on some synthesized inorganic exchangers, as well as commercially available organic ion exchangers were studied and compared. Organic cation exchanger Dowex-50WX8 and organic anion exchangers AG-1X8 and AG-2X8 were utilized. Synthesized inorganic ion exchangers were zirconium titanium phosphate (ZrTiP) of different Zr:Ti mole ratios and ceric tungstate (CeW). The sorption was carried out from mineral acid solutions as well as EDTA and DTPA solutions. The radioactive isotopes, 95 Zr, 95 Nb, 123m Te, 141 Ce and 181 Hf were used to trace the sorption behaviors of the corresponding elements, which were studied in mixtures of them. The differences between the sorption behaviors of the studied metal ionic species on both kinds of ion exchangers were interpreted and discussed in this work.

Bioaccumulation and biosorption characteristics of Mn 2+ ions by both dead and living, non-growing biomass of Gram-positive bacteria Kocuria palustris and Micrococcus luteus isolated from spent nuclear fuel pools were compared. The radioindicator method using radionuclide 54 Mn was applied to obtain precise and reliable data characterizing both processes as well as manganese distribution in bacterial cells. Manganese was mainly found on the surface (biosorption) of live cells of both bacteria and surface sorption capacity increased with Mn concentration in solution. Only 10.0% ( M. luteus ) and 6.3% ( K. palustris ) of uptaken Mn were localized in the cytoplasm (bioaccumulation). Biosorption of Mn by dead bacterial biomass was a rapid process strongly affected by solution pH. Maximum sorption capacities Q max calculated from the Langmuir isotherm and characterizing Mn binding represented 316±15 μmol/g for M. luteus and 282±16 μmol/g for K. palustris. Results indicate that living, non-growing cells showed a higher efficiency of Mn removal than dead biomass. Based on FTIR spectra examination with aim to characterize the surface of K. palustris and M. luteus cells, we confirmed that the phosphate and carboxyl functional groups are involved in manganese sorption onto cell surface by both live and dead bacterial biomass.

In the present work, [ 99m Tc]N-histamine has been labeled using [ 99m Tc≡N] 2+ core. Factors such as, amount of substrate, pH, reaction temperature, in vitro stability and reaction time, have been systematically studied to optimize high radiochemical purity (>99±0.3). Biodistribution studies indicate the suitability of [ 99m Tc]N-histamine as a novel tracer to image brain. The complex of [ 99m Tc]N-histamine may be considered a highly selective radiotracer for brain imaging.

As an alternate extractant for spent fuel reprocessing, the radiolysis properties of TiAP should be systematically studied to evaluate the feasibility of using it in engineering scale. In this paper, the irradiation stability of TiAP was investigated by using the concept of radiolysis ratio and G value. It is found the extent of radiolysis would be increased with the increasing of absorbed doses, but decreased with the increasing of pre-equilibrium aqueous HNO 3 concentration. Furthermore, the radiolysis products were analyzed qualitatively and quantitatively with gas, liquid and ion chromatograph, based on which the possible radiolysis mechanism of TiAP was also concluded.

Bis(2-ethylhexyl)phosphoric acid (HDEHP) is one of the most intensively used extractants in solvent extraction, and its particular interest lies in the its application in nuclear fuel cycle as an extractant supported by macroporous silica-based polymeric resins in solid phase extraction technique. In this study, HDEHP/SiO 2 -P was synthesized by impregnation and immobilization, and we mainly focused on its radiation-resistant properties against γ-rays. It was found that HDEHP/SiO 2 -P still had good adsorption and separation properties after γ-irradiation by batch experiment. The uptake capacity of Gd(III) towards HDEHP/SiO 2 -P decreased slightly after irradiation. HDEHP/SiO 2 -P did not show any changes in the characterization of infrared spectroscopy and thermogravimetric analysis before and after irradiation. UPLC-Q-TOF-MS was employed to investigate the reaction mechanism in radiolysis of HDEHP in irradiated filter liquor. HDEHP/SiO 2 -P had a satisfactory radiation-resistance and chemical stability, even though it was exposed to the high absorbed dose of 500 kGy by γ-rays.