Volume 107, Issue 5

Separation of neptunium from a mixture of actinides viz. uranium, neptunium and plutonium was evaluated using two monoamides, viz. N , N ,-dihexyl octanamide (DHOA) and N , N ,-dihexyl decanamide (DHDA). The extraction of actinides with these ligands followed the order: U(VI)>Np(IV)>>Pu(III). Poor extraction of Pu(III) with both the amides (DHOA and DHDA) was exploited for the mutual separation of U, Pu and Np. At 3 M HNO 3 , DHDA was a better extractant for all the three metal ions while Pu(III) extraction was one order magnitude lower with DHOA as compared to that seen with DHDA. Consequently, better separation factor of U(VI)/Np(IV) over Pu(III) was obtained with DHOA. In the actinide mixed solution, Pu was reduced to its +3 state followed by selective extraction of U(VI) and Np(IV). Subsequently, the mutual separation of U(VI) and Np(IV) was carried out by selective complexation and stripping of Np(IV) by acetohydroxamic acid (AHA) at 2 M HNO 3 , where U(VI) remained in the organic phase. The purity of the separated actinides was confirmed by alpha spectrometry. A separation scheme for the separation of Np from radioactive waste/high level waste has been proposed.

Adsorption of thorium onto nitric acid modified multi-walled carbon nanotubes was investigated by central composite design as a function of contact time, pH, initial thorium concentration and temperature. The results showed that optimum uptake capacity was 65.75±2.23 mg·g −1 with respect to pH=4, initial thorium concentration of 100 mg·L −1 , 25 °C and 15 min contact time. Thermodynamic parameters [standard enthalpy (Δ H 0 ), entropy (Δ S 0 ), and free energy (Δ G 0 )] were calculated, and the results indicated that adsorption was endothermic. Langmuir, Freundlich and Dubinin-Radushkevich isotherms have been investigated in order to characterize the adsorption process in the range of 25–100 mg·L −1 initial thorium concentration. The Freundlich isotherm is the best suited as a model because it has the highest correlation coefficient (R 2 =0.9485). The pseudo-second order kinetics well defined the adsorption process.

Bentonite is the candidate buffer and backfill material in the deep geological repositories. Montmorillonite (Mt) is the major clay minerals of bentonite. Over a long period of time, the interaction of corrosion products from overpack and/or cansister with clay minerals is expected to result in formation of Fe(III)-Mt, a plausible alterated product. In this context, it is important to understand the properties of Fe-Mt in comparison with original clay mineral, Na-Mt. In the present study, sorption behavior of Cs(I), long lived fission product ( 135 Cs, t 1/2  = 2.3 × 10 6 years; 137 Cs, t 1/2  = 30.1 years) with high fission yield, on Fe(III)-Mt is investigated. Batch sorption studies are conducted at varying pH (3–9), ionic strength (0.001–1 M) and Cs(I) concentration (10 −10 to 0.05 M). The distribution coefficient (K d ) of Cs(I) on Fe(III)-Mt was found to be independent of pH except at low pH, indicating ion exchange mechanism as dominant interaction mode for Cs(I). It was further verified by ionic strength variation which depicted decrease in Cs(I) sorption with increasing ionic strength. Adsorption isotherm of Cs(I) was found to be linear over the concentration range of 10 −10 to 10 −3 M Cs(I). The Fe released from Fe(III)-Mt during the Cs(I) sorption was found to be not more than 0.2 ppm. However, on lowering the pH and increasing the ionic strength, the Fe release increased. Furthermore, the apparent diffusion coefficient for Cs(I) in Fe(III)-Mt has been determined.

Novel graphene-sugarcane bagasse-carboxy methyl cellulose (GSCCMC) nanocomposite have been synthesized via freeze-drying technique after preparation of graphene from natural graphite by modified Hummer method and evaluated as adsorbent for sorption of 60 Co(II)-radionuclides from radioactive waste solution and real wastewater samples using a series of batch adsorption experiments and compared with graphene. The synthesized (GSCCMC) nanocomposite was characterized using Fourier transformer infrared (FT-IR), Transmission electron microscope (TEM), Thermal analysis, Elemental analysis, Specific Surface area (S BET ) and X-ray diffraction (XRD), which confirmed the successful formation of graphene-sugarcane bagasse-carboxy methyl cellulose (GSCCMC) nanocomposite. Different parameters affecting the removal process including pH, contact time and metal ion concentration were investigated. Isotherm and kinetic models were studied. Adsorption kinetics described well by pseudo-second-order. The Langmuir model provides a better fitting than the Freundlich and Temkin models and the maximum adsorption capacity from Langmuir model were found to be 0.4186 and 0.2424 mol/g for (GSCCMC) nanocomposite and graphene (G), respectively. From Dubinin–Radushkevich (D–R) isotherm model, the sorption energy (E)-values of graphene (G) and (GSCCMC) are 10.16 and 10.564 kJ/mol, respectively and this mean the adsorption of 60 Co(II)-radionuclides can be explained by chemisorption process, which is characteristic of ion exchange. Desorption of 60 Co(II)-radionuclides from loaded (GSCCMC) nanocomposite was studied using different eluents (0.1 M HCl, 0.1 M NaOH and H 2 O). The data illustrated that 0.1 M HCl solution showed maximum desorption percent (D%) than other eluents. The economic viability of the adsorption process for the removal of 60 Co(II) from wastewater samples was studied. The result indicated that the cost for preparation of (GSCCMC) nanocomposite is lower than for (GSCCMC) nanocomposite that prepared from purchase the graphene powder. Therefore, the synthesized (GSCCMC) nanocomposite was used as regenerated material for sorption of 60 Co(II)-radionuclides from aqueous solutions and can be used for many times as a cost-effective and environmental friendly material in wastewater treatment.

The manuscript deals with the sorption of Am(III) and Eu(III) from pH medium using chitosan functionalized with dendrimer like polyamidoamine (PAMAM) polymers up to third generation. The PAMAM polymers were introduced into chitosan by two step processes and were characterized by various instrumental techniques like FTIR, XRD, TG-DTA. The sorption process was highly pH dependent for both Am(III) and Eu(III) with increasing trend for higher pH of the solution. Kinetics of equilibration was found to be fast with equilibrium attained in 10 min for both the metal ions. Pseudo 2 nd order kinetics mechanism was found to be followed for both Am(III) and Eu(III). The sorption process of Eu(III) was found to fit the Langmuir isotherm model with maximum sorption capacity of 6.01 mg/g. There was no effect on the generation of PAMAM Dendron on the efficiency, kinetics or sorption capacity for Am(III) as well as Eu(III). The synthesized different generation of PAMAM functionalized chitosan is a promising material for removal of actinides and lanthanides from waste water solution.

Ruthenium ( 106 Ru), a notorious fission product in nuclear reprocessing cycle, which gets partitioned at each step needs to be recovered. The recovery of Ru from acidic high level waste (HLW) is of great importance to the nuclear fuel cycle. Quantitative recovery of Ru was achieved from acidic feeds using oxidative trapping mechanism strategy where NaIO 4 was used as an oxidant to convert different species of Ru in acidic phase to RuO 4 while n-dodecane was used as trapping agent for RuO 4 . Stripping was attempted using NaOH and NaClO mixture. Attempt was made to optimize various parameters for 103 Ru extraction and stripping. 103 Ru tracer spiked simulated high level waste was used to understand the 103 Ru behaviour in actual waste. The composition of stripping solution (alkaline hypochlorite) was also optimized to have >95% Ru into the aqueous phase in ca. 180 min.

Widespread deficiency of soil macro (N) and micro nutrient (Fe) limit crop productivity and nutritional quality of the produce worldwide. Iron is relatively immobile in plants however, its retranslocation can be facilitated by naturally produced chelator in the leaves. Synthesis of these metal-chelators depends on N nutrition of crops. The present study uses 59 Fe tracer to measure the contribution of in-plant remobilization (from fully developed 2 nd older leaf (OL) to a younger developing 3 rd leaf (YL)) of relatively immobile iron towards N and Fe deficiency stress tolerance in Fe efficient bread and Fe inefficient durum wheat. Dual nutrient deficiency of nitrogen and iron induced senescence and hastened the process of chlorophyll degradation and induced a higher 59 Fe remobilization from OL to YL. Further, 59 Fe retranslocation was also highest under dual nutrient deficiency (N−Fe−). Percent 59 Fe retranslocated into the YL of bread and durum wheat, respectively was higher in Fe deficient (N+Fe− and N−Fe−) than Fe sufficient (N+Fe+ and N+Fe−) treatments. Results clearly reveal that Fe deficiency tolerance response under N and Fe deficiency is chiefly determined an efficient Fe uptake and Fe retranslocation, respectively in the bread and the durum wheat.

The bulk extraction of Nd(III) from 4 M nitric acid medium was studied in a solution of N , N -di-octyl-2-hydroxyacetamide (DOHyA) in n -dodecane as a function of γ absorbed dose up to 750 kGy. The average size of reverse micellar aggregates in the irradiated and un-irradiated DOHyA samples after the extraction of Nd(III) was measured by dynamic light scattering (DLS) spectroscopy. The effect of absorbed dose of γ radiation and concentration of Nd(III) in the organic phase on the aggregation behavior of DOHyA was investigated by DLS measurements and ATR-FTIR spectroscopy. The data on irradiated and un-irradiated samples were compared. FT-IR analysis of the irradiated samples of DOHyA showed the formation of degradation products which were mainly identified as hydroxyacetic acid and primary or secondary amines.