Biphasic kinetic investigations on the evaluation of non-salt forming reductants for Pu(IV) stripping from tributyl phosphate and N,N-dihexyl octanamide solutions in n-dodecane

The relative stability of different oxidation states of actinide elements is influenced by the nature of complexes formed and redox equilibria in aqueous/non-aqueous solutions. The reduction/stripping studies on Pu(IV) ions from loaded organic phases of 1.1 M tributyl phosphate and of 1.1 M N,N-dihexyl octanamide in n-dodecane were studied using organic soluble tert-butyl hydroquinone (TBH) and aqueous soluble reductants like acetaldoxime (AX) and hydroxyurea (HU). These studies were carried out as a function of reductant and nitric acid concentration (0.5–4 M HNO₃) and of time. The changes in Pu oxidation states were followed by spectrophotometry for TBH and by distribution ratio values for AX and HU as reductants. Spectrophotometric investigations using TBH as reductant showed that it was desirable to strip Pu(III) formed after reduction of Pu(IV) in the organic phase, which may otherwise be reconverted to extractable Pu(IV) by in situ generated HNO₂ from oxidative degradation of TBH to tert-butyl quinone. Similarly, the biphasic reduction/stripping of Pu(IV) using AX and HU as reductant rate was affected adversely with increased aqueous phase acidity. This data will help in the accurate simulation of Pu separation processes using these reductants in mixer-settlers/pulsed columns or centrifugal contactors.     

Experimental and Theoretical Studies on Synthesized Compounds as Corrosion Inhibitor for Mild Steel in Hydrochloric Acid Solution

Imidazole derivatives, namely, 1-((1-(piperazinomethyl)-1H-benzoimidazol-2-yl)methyl)-2-phenylhydrazine (PBIP), and 1-((1-(morpholinomethyl)-1H-benzoimidazol-2-yl)methyl)-2-phenylhydrazine (MBIP) were synthesized and investigated as inhibitors for mild steel corrosion in 15% HCl solution using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. It was found that the inhibition efficiency of both the inhibitors increases with increase in concentration of inhibitors and decreases with increase in temperature. The inhibitors, PBIP and MBIP, show corrosion inhibition efficiency of 92.6% and 91.4% at 300 ppm concentration, respectively, at 303 K. Polarization studies showed that both the studied inhibitors were of mixed type in nature. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed for surface study of uninhibited and inhibited mild steel samples. The semi-empirical AM1 method was employed for theoretical calculations.     

N,N-Dialkyl amides as extractants for spent fuel reprocessing: an overview

Reprocessing of spent nuclear fuel is vital for the long-term global nuclear power growth and is the major motivation for developing novel separation schemes. Conventionally, PUREX and THOREX processes have been proposed for the reprocessing of U and Th based spent fuels employing tri-n-butyl phosphate (TBP) as extractant. However, based on the experiences gained over last five–six decades on the reprocessing of spent fuels, some major drawbacks of TBP have been identified. Evaluation of alternative extractants is, therefore, desirable which can overcome at least some of these problems. Extensive studies have been carried out on the evaluation of N,N-dialkyl amides as extractants in the back-end of the nuclear fuel cycle for addressing the issues related to the reprocessing of U and Th based spent fuels. Under advanced fuel cycle scenario, efforts are also being made by countries with a developed nuclear technological base to provide safe nuclear power to other countries and to minimize proliferation concerns worldwide. This paper presents an overview of studies carried out in our laboratory on different aspects of reprocessing of U and Th based spent fuels employing N,N-dialkyl amides as extractants.     

A Facile Method for Detection and Speciation of Inorganic Selenium with Ion Chromatography

Chromatographia - In this work, we present a new method for the determination and speciation of selenium in water with ion chromatography (IC) using a conductometric detector. Chromatographic...     

A simple and cost-effective synthesis of sulfated β-cyclodextrin and its application as chiral mobile phase additive in the separation of cloperastine enantiomers

Journal of Inclusion Phenomena and Macrocyclic Chemistry - A simple and cost-effective method for the synthesis of sulfated β-cyclodextrin, one of the most widely used chiral mobile phase...     

Rotary disc bioreactor-based approach for bacterial nanocellulose production using Gluconacetobacter xylinus NCIM 2526 strain

Bacterial nanocellulose (BNC) is an indomitable biomaterial of utmost usage in different technological areas. Previously, the BNC production has been reported in the simplified bioreactors. Thus, pioneering bioreactor-assisted strategies are desirable for the commendable BNC production. Advanced bioreactors must be corroborated along with different bacterial strains to obtain creditable BNC yield. This study deals with BNC production in rotary disc bioreactor (RDBR) using Gluconacetobacter xylinus NCIM 2526 strain. RDBR-based production of BNC provided 189?±?14 gL^?1 of wet BNC, i.e., equivalent to 6.6?±?0.3 gL^?1 dry BNC yield in 10 days. However, in static cultivation mode, 56?±?12 gL^?1 wet weight of BNC, corresponding to 2.4?±?0.4 gL^?1 dry weight, was produced. Thus, BNC production was approximately 2.75 folds higher in RDBR than statically produced BNC from the same volume of the media. The sugar to BNC conversion yield (12.2?±?0.8%) was doubled in RDBR-based production as compared to static BNC production (6.2?±?1.4%) with efficient sugar consumption (90.0?±?3.3%). The maximum amount of BNC was produced at 7 RPM and pH 6. RDBR-based BNC showed a more hydrophilic nature than statically produced BNC. The RDBR might be appropriate for large-scale BNC production, especially for wet-end applications, as an ample amount of BNC can be produced from a single fermentation process. These BNC pellicles might have the potential for biomedical applications like wound dressings, biofacial masks, hydrogels, and tissue engineering scaffolds.

     

Exchange-mediated spin-lattice relaxation of Fe3+ ions in borate glasses

Spin-lattice relaxation times (T1) of two borate glasses doped with different concentrations of Fe2O3 were measured using the Electron Spin-Echo (ESE) technique at X-band (9.630 GHz) in the temperature range 2-6K. In comparison with a previous investigation of Fe3+-doped silicate glasses, the relaxation rates were comparable and differed by no more than a factor of two. The data presented here extend those previously reported for borate glasses in the 10-250K range but measured using the amplitude-modulation technique. The T1 values were found to depend on temperature (T) as T(n) with n approximately 1 for the 1% and 0.1% Fe2O3-doped glass samples. These results are consistent with spin-lattice relaxation as effected by exchange interaction of a Fe3+ spin exchange-coupled to another Fe3+ spin in an amorphous material.     

High-power and high-temperature THz quantum-cascade lasers based on lens-coupled metal-metal waveguides

A metal-metal waveguide quantum cascade laser with an abutted silicon hyperhemispherical lens is demonstrated at ~4.1 THz. The device produced 145 mW of peak pulsed power at 5 K with a wall-plug power efficiency of 0.7%, lasing up to a maximum operating temperature of 160 K. The far-field beam pattern has a full width at half-maximum value of ~4.8 degrees in the H plane. The same device produced ~26 mW of peak power using a Winston cone instead of a lens, lasing up to 165 K. The large increase in output power is mainly attributed to an increase in collection efficiency.     

N-donor stabilized complexes of nickel(II) diphenyldithiophosphates: single-crystal X-ray,HSA and computational analysis

Transition Metal Chemistry - Nickel(II) complexes with octahedral coordination stabilized by N-donor ligands corresponds to [{(ArO)2PS2}2Ni·L2] [Ar = 4-(C2H5)C6H4 (3), and...     

Degeneracy in one dimension: Role of singular potentials

That the bound energy eigenstates of one-dimensional quantum systems can be degenerate in the presence of specific singular or supersingular potentials is demonstrated by choosing a family of bistable and other oscillators. Relevance of our study to spectroscopic observations is noted. Quasi-degeneracy is found even in the absence of any singularity in the potential and the importance of tunneling is highlighted in this context to analyze the general nature of such potentials leading to double degeneracy. Additionally, the case of spiked oscillators is discussed with particular reference to the “Klauder phenomenon,” revealing clearly that the mere presence of singularity in the potential is not a sufficient criterion for the occurrence of degeneracy. © 1996 John Wiley & Sons, Inc.