The extraction of palladium/II/ with diphenyl-2-pyridylmethane /DPPM/ in benzene has been investigated from thiocyanate-nitrate media and optimized. Thiosulphate ions showed strong interference and reduced the extraction below 1%. Separation factors determined for most of the elements were better than 103. This extraction method affords palladium preconcentration and its separation from Sc/III/, Co/II/, Cu/II/, Zn/II/, Se/IV/, Sr/II/, Ru/III/, Cd/II/, Cs/I/ and Eu/III/. Few possible applications of such separations have been cited.
The complexes formed by photosubstitution of pyrazine (Pz) in octacyanomolybdate(IV) and -tungstate(IV) with 8-hydroxyquinoline have been assigned the formulae [Mo(CN)2(OH)2(Pz)2(OX)] and [W(CN)2(OH)2(Pz)2(OX)·1.5H2O]. Coordination of Pz as an unidentate ligand by donating a lone pair of electron from nitrogen is shown by an absorption peak between 8–11 µ. Mechanism for the thermal decomposition of the complexes has been given. The formation of tungsten metal as residue in case of II has been confirmed by XRD analysis. The kinetic and thermodynamic parameters like activation energy (Ea), pre-exponential factor (A) and entropy of activation (
S#) were calculated employing different integral methods of Doyle, Coats and Redfern and Arrhenius.
H for each stage of decomposition was obtained from DSC.
Arsenic content in drinking water and in scalp hair of the arsenic affected areas in Bangladesh were measured using energy dispersive X-ray fluorescence (EDXRF) to determine the contribution of drinking water to body burden and health risks. Around 61% of the water analyzed from tube-wells has arsenic content above 0.05 mg/l and about 13% have arsenic content above 0.01 mg/l. The mean concentration of arsenic in contaminated water is about 0.26 mg/l with the maximum level of 0.83 mg/l. The contaminated water thus contributes a significant amount to the arsenic budget in humans in Bangladesh and consequently, to their health hazards. The average concentration of arsenic in hair of a patient group drinking contaminated water is 14.1 mg/kg where the normal levels are <3.0 mg/kg. The distribution of arsenic in water and in hair is compared and discussed with the data reported in the literature. The daily dietary intake value of arsenic by the adult population in Bangladesh is estimated and assessed signifying health effects.
The extraction of silver from aqueous thiocyanate-perchlorate solutions using diphenyl-2-pyridylmethane (DPPM) in benzene has been investigated. The variables such as concentrations of perchloric acid, thiocyanate and DPPM influencing the extraction have been optimized. Maximum extraction has been achieved from 0.01 M perchloric acid solution containing 0.01 M potassium thiocyanate in 0.075 M DPPM in benzene. The extraction was found to be independent of silver concentration in the range from 10–4–10–6 M. The influence of several anions on the extraction was examined; only thiosulphate interfered seriously and reduced the extraction below 1%. Thus 0.1M potassium thiosulphate was found to back-extract silver quantitatively in one step. Under selected optimal conditions, very small extraction (<1%) was observed for trivalent Gd, Dy, Ho, Tm, Yb, Lu; Cs(I) and Cd(II) and separation factors for these elements were better than 103. Only Sn(IV) exhibited quantitative extraction (>99%). This extraction procedure can be used for the preconcentration of silver and tin or their separation from rare earths mentioned above.
The separation of Am/Cm was studied in batch and dynamic experiments. It was achieved chromatographicaly on the chelating
ion exchanger Dowex-Chelating-Resin-Al making use of the great difference between the complexing ability of trivalent and
pentavalent oxidation states. For this purpose, the influence of some variables on the Am/Cm separation factor and on the
stability of the adjusted pentavalent state was studied, e.g. the weight of ion exchanger, the time of contact and the pH-values
of the solutions. Comparative investigations were carried out on the pentavalent ions of neptunium, plutonium and americium
as well as on the hexavalent ions of plutonium and americium, where a significant difference in their behaviours was found.
The hydrogen isotope radiolytic yields, G(H2), G(HD) and G(D2) were determined in H2O/D2O mixtures under chemical conditions close to a LOCA in a PHWR like Atucha I Nuclear Station, that is 2·10–3 MH3BO3 and p(H+D)=8.5±0.2. The total hydrogen radiolytic yield G(H2+HD+D2) as a function of the deuterium atom fraction goes through a flat maximum at about 0.58. This result in dicates that the 4% flammability limit for hydrogen in the reactor's containment with be reached sooner than what is expected assuming a linear combination of pure H2 and D2 radiolytic yields. Hydrogen radiolytic production in 10–3 M KBr in H2O/D2O mixtures gives the same results as in the boric solutions suggesting a bimolecular B(OH)
+OH reaction. Identical isotope concentration factors were calculated for both solutions.
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.
La2Mo2O9 (LMO) was synthesized at lower temperature 973 K (LT-phase) by ceramic route. Differential thermal analysis (DTA) scan of
LT-phase of LMO showed α→β transition at 843 K during heating and β→α conversion via a metastable γ-phase during cooling.
This was also confirmed by thermo-dilatometry and impedance spectroscopy. La2Mo1.95V0.05O9-δ (LMVO), La1.96Sr0.04Mo2O9-δ (LSMO) and La1.96Sr0.04Mo1.95V0.05O9-δ (LSMVO) were prepared in a similar way. These compounds exhibited α→β transition on heating with shift in transition temperature,
but the existence of γ-phase during cooling disappeared. Substitution increased the ionic conductivity of α-phase and reduced
that of β-phase.