Use of organophosphorus extractants impregnated on silica gel for the extraction chromatographic separation of minor actinides from high level waste solutions

Silica-gel has been used as an inert support for the extraction chromatographic separation of actinides and lanthanides from HNO₃ and synthetic high level waste (HLW) solutions. Silica-gel was impregnated with tri-butyl phosphate (TBP), to yield STBP; 2-ethylhexyl phosphonic acid, mono 2-ethylhexyl ester (KSM-17, equivalent to PC-88A), SKSM; octyl(phenyl)-N,N-diisobutyl carbamoylmethylphosphine oxide (CMPO), SCMPO; and trialkylphosphine oxide (Cyanex-923), SCYN and sorption of Pu(IV), Am(III) and Eu(III) from HNO₃ solutions was studied batchwise. Several parameters, like time of equilibration, HNO₃ and Pu(IV) concentrations were varied. The uptake of Pu(IV) from 3.0M HNO₃ followed the order SCMPO>SCYN>SKSM>STBP. With increasing HNO₃ concentration, D _Pu increased up to 3.0M of HNO₃ for STBP, SKSM and SCMPO and then decreased. In the case of Am and Eu with SCMPO, the D values initially increased between 0.5 to 1.0M of HNO₃, remained constant up to 5.0M and then slightly decreased at 7.5M. Also, the effects of NaNO₃, Nd(III) and U(VI) concentrations on the uptake of Am(III) from HNO₃ solutions were evaluated. With increasing NaNO₃ concentration up to 3.0M, D _Am remained almost constant while it was observed that it decreases drastically by adding Nd(III) or U(VI). The uptake of Pu and Am from synthetic pressurized heavy water reactor high level waste (PHWR-HLW) in presence of high concentrations of uranium and after depleting the uranium content, and finally extraction chromatographic column separation of Pu and Am from U-depleted synthetic PHWR-HLW have been carried out. Using SCMPO, high sorption of Pu, Am and U was obtained from the U-depleted HLW solution. These metal ions were subsequently eluted using various reagents. The sorption results of the metal ions on silica-gel impregnated with several phosphorus based extractants have been compared. The uptake of Am, Pu and rare earths by SCMPO has been compared with those where CMPO was sorbed on Chromosorb-102, Amberchrom CG-71 and styrene divinylbenzene copolymer immobilized in porous silica particles.     

o-Nitrobenzoyl group as a new amino protecting group for peptide synthesis and the synthesis of some anthranilyl peptides

N (o-nitrobenzoyl)amino acids can be coupled with other amino acids using DCC and the resulting product on hydrogenation gives peptides, containing the anthranilyl group as —NH₂ end group. N (anthranilyl)amino acids or peptides can also be obtained by reaction of isatoic anhydride on amino acids or peptides. The anthranilyl end group is easily cleaved by metal (Cu⁺²) catalysed hydrolysis to give α-amino acid peptides and the insoluble copper(II) anthranilate.     

Diacetylenic Derivatives of Fe2(CO)6(μ-EE′): Spectroscopic Investigations of Fe2(CO)6{μ-EC(H) = C(C≡ CMe)E′} (E = E′, E ≠ E′; E, E′ = S, Se, Te)

The diacetylenic adducts, Fe₂(CO)₆{-EC(H) = C(C CMe)E} (E = E, E E; E, E = S, Se, Te) (1–8) have been obtained from the room temperature stirring of Fe₂(CO)₆(-EE) with HC CC CMe in methanol solvent containing sodium acetate. Compounds 1–8 have been characterized by IR and multinuclear NMR (¹H, ¹³C, ⁷⁷Se, and ^l25Te) spectroscopy. Trends in the chemical shifts of ⁷⁷Se and ¹²⁵Te NMR spectra of Fe₂(CO)₆{-EC(H) = C(C CMe)E} with a variation of EE are discussed.     

UVB-induced photodamage to phycobilisomes of Synechococcus sp. PCC 7942

The effect of UVB irradiation on the phycobilisomes (PBSs) of Synechococcus sp. PCC 7942 cells was studied. The sucrose density-gradient-isolated PBSs from in vivo UVB-treated (280–320 nm) cells showed a strong decrease in β-phycocyanin (βPC) and -phycocyanin (PC) polypeptides. In addition to a decrease in the linker polypeptides LCM 75 (linker connecting the core to the thylakoid membranes), LR 33 (linker in the rod structure), LRC 31.5 (linker connecting the rod to the core) and LRC 29. In vitro UVB treatment of gradient-isolated intact PBSs for 1 h had no effect on any of the constituent polypeptides, and only after 2 h was a degradation of LCM 75 and LR 33 and a decrease in βPC evident. Further investigation of phycobiliproteins (4 h of UVB irradiation) using polyclonal antibody directed against purified whole PBSs revealed that, in vivo, there was a gradual decline in the levels of LCM 75, LR 33, LRC 31.5, LRC 29, βPC and PC.     

Nanostructured ZrO2 and Zr‐C‐N Coatings from Chemical Vapor Deposition of Metal‐Organic Precursors

Nanocrystalline zirconium carbonitride (Zr‐C‐N) and zirconium oxide (ZrO₂) films were deposited by chemical vapor deposition (CVD) of zirconium‐tetrakis‐diethylamide (Zr(NEt₂)₄) and ‐tert‐butyloxide (Zr(OBu^t)₄), respectively. The films were deposited on iron substrates and characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The Zr‐C‐N films show blue, golden brown or bronze colours, with colour stability depending upon the precursor composition (pure metal amide or mixed with Et₂NH). The deposition temperature showed no pronounced effect on the granular morphology of the Zr‐C‐N films. The XRD data of the films correspond to the formation of carbonitride phase whereas the XPS analyses revealed a strong surface oxidation and incorporation of oxygen in the film. The films deposited using a mixture of Zr(NEt₂)₄ and Et₂NH showed higher N content, better adhesion and scratch resistance when compared to films obtained from the CVD of pure Zr(NEt₂)₄. Subject to the precursor composition and deposition temperature (550‐750 °C), the microhardness values of Zr‐C‐N films were found to be in the range 2.11‐5.65 GPa. For ZrO₂ films, morphology and phase composition strongly depend on the deposition temperature. The CVD deposits obtained at 350 °C show tetragonal ZrO₂ to be the only crystalline phase. Upon increasing the deposition temperature to 450 °C, a mixture of tetragonal and monoclinic modifications was formed with morphology made up of interwoven elongated grains. At higher temperatures (550 and 650 °C), pure monoclinic phase was obtained with facetted grains and developed texture.     

Ru(II) complexes imparting N2O2 donor bis chelating ligand N,N-bis(salicylidine)-hydrazine in unusual coordination mode

The synthesis and characterization of binuclear ruthenium complexes [{(η⁶-C₆H₆)Ru}₂(μ-bsh)₂] (1), [{(η⁶-C₁₀H₁₄)Ru}₂(μ-bsh)₂] (2), [{(η⁶-C₆Me₆)Ru}₂(μ-bsh)₂] (3), and rhodium complex [{(η⁵-C₅Me₅)RhCl}₂(μ-bsh)] (4) (bsh=N,N^′-bis(salicylidine)-hydrazine dianion) are reported. The complexes have been fully characterized by analytical and spectral techniques and unusual coordination mode of the ligand H₂bsh has been confirmed by single crystal X-ray analysis of the complex 2. Structural data revealed extensive inter- and intra-molecular C-H?O and C-H?π interactions and involvement of methyl and isopropyl hydrogen from the p-cymene in hydrogen bonding.     

Conformational studies of 3,4-dideoxy furanoid sugar amino acid containing analogs of the receptor binding inhibitor of vasoactive intestinal peptide

Conformational analysis of vasoactive intestinal peptide (VIP) receptor binding inhibitor Leu¹-Met²-Tyr³-Pro⁴-Thr⁵-Tyr⁶-Leu⁷-Lys⁸1 by various NMR techniques and constrained molecular dynamics (MD) simulation studies revealed that the molecule had a turn structure involving its Tyr³-Pro⁴-Thr⁵-Tyr⁶ moiety with intramolecular hydrogen bond between Tyr⁶NH→Tyr³CO. In order to mimic the structure of 1, peptidomimetic analogs 2-4 were synthesized using conformationally constrained scaffolds of 3,4-dideoxy furanoid sugar amino acids (2S,5R)-ddSaa1 5 and its enantiomer (2R,5S)-ddSaa2 6. All these analogs displayed well defined three-dimensional structures akin to that found in 1. Peptides 2 and 3, which differed only in the sugar amino acid stereochemistry, show propensity of structures with identical intramolecular hydrogen bonds between ThrNH→MetCO. A similar structure with a hydrogen bond between TyrNH→MetCO was observed in 4.     

Hydroarylation of alkynes and alkenes through alumina-sulfuric acid catalyzed regioselective CC bond formation

A highly atom-efficient synthetic protocol for hydroarylation of terminal-aryl alkynes and styrene through the regioselective CC bond formation via the electrophilic addition of naphthols and substituted phenols has been developed using alumina-sulfuric acid as a heterogeneous supported solid acid catalyst. This methodology shows excellent regioselectivity and affords the desired product in good to excellent yield. The heterogeneous catalyst can also be recycled efficiently without much loss of activity.     

Electrocatalytic treatment of waste: studies on discoloration of an industrial azo dye effluent

A textile dye effluent containing chiefly reactive azo dyes has been treated electrochemically for discoloration and COD (chemical oxygen demand) reduction at different current densities, flow rates and dilution. Experiments have been carried out in a thin electrochemical reactor under single pass conditions using a dimensionally stable catalytic anode (DSA) and a stainless steel cathode.