Extraction of $$ {\text{Np}}^{4+} $$ and $$ {\text{NpO}}_{2}^{2+} $$NpO22+ from Nitric Acid Medium Using TODGA in Room Temperature Ionic Liquids

Extraction of Np⁴⁺ and \( {\text{NpO}}_{2}^{2 + } \) was carried out from nitric acid feeds using solutions of N,N,N′,N′-tetra-n-octyldiglycolamide (TODGA) in two imidazolium-based room temperature ionic liquids, viz., 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl) imide ([C₄mim][NTf₂]) and 1-octyl-3-methylimidazolium bis(trifluoromethanesulphonyl) imide ([C₈mim][NTf₂]). The extraction equilibrium was attained within 2 h for both the metal ions in both the ionic liquids. While a cation exchange mechanism is proposed for the extraction of \( {\text{NpO}}_{2}^{2 + } , \) an ion-pair mechanism of extraction is proposed for the Np⁴⁺ ion. The nature of the extracted species was determined by carrying out experiments at varying concentrations of TODGA, and species of the type Np(L)₂(NO₃)₄ and NpO₂(L)²⁺ were found to be extracted in 3 mol·dm^?3 HNO₃. The identification of these extracted species was also supported from the variable nitrate and C₄mim⁺ ion concentration experiments.     

Synthesis,characterization and thermal behaviour of adducts

The photoproduct of octacyanomolybdate(IV) and -tungstate(IV) with ethylenediamine and triethylenetetramine give complexes of the type K₃[Mo(O₂)(O)(OH)(C₉H₇ON)]·3C₉H₇ON I, K₂[W(O₂)(O) (C₉H₇ON)₃] II and K₃[Mo(CN)₃(OH)₄(C₉H₇ON)]·2C₉H₇ON·3H₂O III with 8-quinolinol (oxine). The IR spectra of the complex III shows the presence ofv(CN) peaks in the range 2047–2108 cm^?1 and oxine groupv(C-O) in the complex I, II and III in the range of 1100–1150 cm^?1. The lower region of IR spectra shows the M=O stretching while the higher thev(N-H) andv(OH). Thermal studies show the removal of uncoordinated water at 131?C from complex III. The decomposition of complexes I and II start from 150 and 212?C respectively. Oxine and cyano molecules were removed in stages at higher temperatures. The final product of the thermal decomposition was oxide which was of polymeric nature. The kinetic parameters viz. order of reaction ‘n’ and activation energy ‘E’ were determined by different methods.     

Kinetics and mechanism of reaction between mercuric bromoiodide and silver iodide in solid state

Kinetics and the mechanism of the reaction between mercuric bromoidide and silver iodide in solid state were studied by X-ray, chemical analysis, thermal, and electrical conductivity measurements. HgBrI and AgI react in the molar ratio 1:3 to give AgBr and Ag₂HgI₄. The data for the lateral diffusion fit best in the equation X_iⁿ = kt. It has been established that the reaction proceeds via a vapor phase diffusion-controlled mechanism through counterdiffusion of Ag⁺ and Hg²⁺. There also seems to be some evidence for the formation of solid solutions between reactant and product phases.     

THE OXIDATION OF CHOLESTEROL BY HYDROXYL RADICAL

Abstract— The oxidation of chblesterol by hydroxyl radical generated by ⁶⁰Co y-radiolysis of aqueous cholesterol dispersions or of dispersions saturated with N₂O ave in low yields the products 38-hydroxy-cholest-5-en-7-one. the epimeric cholest-5-ene-3β,7-diols, 5,6α-epoxy-5α-cholestan-3β-ol, 5.6β-epoxy-5β-cholestan-3,β-ol, and 5α-cholestane-38,5,6β-triol. Sterol hydroperoxides were not detected except in the radiolysis of dispersions saturated with oxygen.     

Early stages of LiX,BeH2X,and BH3X pyrolysis (X stands for NH3 or OH2): A theoretical study of weak dative complex stability

In this work, we study theoretically the thermal decomposition of weak dative complexes (namely, the complexes between BH₃, BeH₂, or LiH and ammonia or water). The most accurate calculations have been carried out at the MP 4sdtq/6-311++G (3df,2p) level on MP 2full/6-31G ** fully optimized geometries. The transition structures for hydrogen evolution are described. The rate constants were obtained using conventional transition-state theory. Stability conditions for the complexes were considered. Water complexes are less stable than are the corresponding ammonia derivatives. Lithium complexes seem to be very unstable. It seems that beryllium compounds could be synthesized. Borane derivatives are known experimentally. We find, as observed, that the first hydrogen evolution occurs only above room temperature. Iminoborane seems not to be easily accessible under pyrolysis conditions. Other reactions require less activation energy. Finally, the early stages of the ammonia–borane pyrolysis and paths to open-chain polymers as well as to cyclic structures are described. © 1993 John Wiley & Sons, Inc.     

Theoretical study of hydrogen abstraction reactions CH4 + R → CH3 + HR,geometrical, energetical and kinetical aspects

Five hydrogen abstraction reactions, CH₄ + R CH₃ + HR have been studied usingab initio SCF and CI methods. R was successively chosen as H, CH₃, NH₂, OH and F. Geometries were fully optimized at SCF level and energies were computed at CI level for products, reactants and transition states. Quadratic hypersurfaces were fitted in the neighborhood of the most important points of the potential energy hypersurfaces and vibrational analysis were performed thereupon. Wigner's and Christov's approximations were used to obtain an idea of the importance of tunneling of H atoms through the reaction barrier, and this effect was shown to be non-negligible. Finally, rate constant calculation were carried out at different temperatures.Chercheur Qualifié au Fonds National Belge de la Recherche Scientifique.     

Carbon Paste Electrode Bulk-Modified with the Conducting Polymer Poly(1,8-Diaminonaphthalene): Application to Lead Determination

Carbon paste electrodes modified with conducting polymers for sensitive and selective determination of lead are presented. A novel method for generating a reproducible polymer-coated electrode surface is developed. We prove that 1,8-diaminonaphthalene (1,8-DAN) mixed with a carbon paste electrode leads to a conducting polymer in acidic medium while, in the same medium, this polymer is known to be non-conducting on platinum electrode. The electrode behaviour of poly(1,8-DAN), electropolymerised into carbon paste, was investigated by cyclic voltammetry in the presence of the ferri-ferrocyanide couple.A carbon paste electrode modified with poly(1,8-DAN) was used to determine Pb²⁺ in aqueous solutions. Pb²⁺ ions were firstly complexed and then electrochemically deposited by a potential step to –0.9V. The accumulated lead after reduction was anodically stripped by differential pulse voltammetry. Different parameters, such as pH of the solution, preconcentration time, and electropolymerisation procedures were studied.For a preconcentration time of ten minutes, the calibration graph was linear from 40 to 2070ngmL^–1 with r²=0.998. The detection limit was found to be 30ngmL^–1, and the relative standard deviation was 6%.     

Polydimethylsiloxane–cristobalite composite adhesive system for aerospace applications

The effect of phase‐pure cristobalite (a high temperature crystalline polymorph of silica) on the adhesive characteristics of hydroxyl terminated polydimethylsiloxane (PDMS) was studied. The potential advantages of PDMS/cristobalite composite system as an adhesive for aerospace applications are also discussed. A PDMS/cristobalite composite adhesive system containing different filler contents (0–46 volume percentage, vol%) was prepared. The filler material, phase‐pure cristobalite, was synthesized by the pyrolysis of fused silica at 1400°C. The mechanical, rheological, and thermal characteristics of the composites were studied. A high yield stress (0.151 Pa), shear‐thinning index (1.051), and fast recovery rate were observed for ～34 vol% cristobalite loading, which indicate that PDMS retains its excellent adhesive and flow characteristics even at high filler loading with enhanced mechanical characteristics. Thermal analysis shows the onset of degradation of PDMS shifts to higher temperatures, 372–438°C and 317–417°C in nitrogen and air atmosphere respectively, which shows excellent thermal stability. The residual component yields after thermal degradation of PDMS/cristobalite composite system in nitrogen and air atmosphere show different degradation mechanisms. Copyright © 2008 John Wiley & Sons, Ltd.     

Optimization of modification condition of nano-kaoline as an adsorbent for textile dye removal

In this study, adsorption capacity of textile red dye on alkylated kaolin was investigated through batch mode. Accordingly, raw kaolin was alkylated via NaOH treatment. The work was carried out in two steps. At first step, the effect of various alkylation conditions of kaolin on its dye adsorption performance was studied using the model equation designed by 2-level factorial design. Three factors were changed in two level including NaOH solution temperature (45–75°C), mixing time (3–24 h), and NaOH solution concentration (0.1–2 M). The resultant model showed 91% of the variability in data used to fit dye adsorption capacity values. However, the analysis of variance revealed that the fitted model is high significant. Based on the predicting model, the optimal alkylation conditions with desirability factor of 0.911 were obtained at temperature of 75°C, NaOH concentration of 0.1 M and after 24 h mixing. At step two, chemical content, bonds and functional groups of the treated kaolin, which was prepared based on the optimum condition and compared with the raw kaolin via X-ray fluorescence (XRF) analysis and Fourier transform infrared analysis (FTIR). The results show slight reduction in SiO₂ content. Finally, the adsorption capacity of dye on both treated and raw kaolin was investigated.