The retention and yields after neutron irradiation under standard conditions by ionizing radiation have been studied as a function of the mole fraction of nitrate in NaIO3–NaNO3 mixed-crystals. The effect of nitrate ion on the retention in solid-solution after irradiation was observed. A probable mechanism is suggested.
Based on solvent extraction and fractional precipitation methods, the retention in iodate and periodate targets were measured. Influence of temperature of irradiation in crystalline and solution phase have been observed. Higher retentions were observed in crystalline solids than in corresponding solution phase irradiation at room temperature. The role of physicochemical properties of the salts and the solvent is discussed.
Dissolution effect on recoil128I retention in the form of IO
ion following /n,/ process in potassium periodate target has been studied. A remarkable variation in retention is found both in solid and solution phase with the pH of dissolution. A suitable mechanism is suggested to explain the observed results.
The temperature dependence of the Gibbs free energy difference (ΔG) between the undercooled liquid and the corresponding equilibrium solid has been analysed for metallic glass forming systems
in the frame of the expression obtained by expanding free energies of the undercooled liquid and solid phases in the form
of Taylor's series expansion. The enthalpy difference (ΔH) and the entropy difference (ΔH) between the undercooled liquid and solid phases have also been analysed. The study is made for five different metallic glass
forming materials, Au77Ge13.6Si9.4, Au53.2Pb27.5Sb19.3, Au81.4Si18.6, Mg85.5Cu14.5 and Mg81.6Ga18.4 and a very good agreement is found between calculated and experimental values of ΔG. The ideal glass transition temperature (Tk) and the residual entropy (ΔSR) of these materials have also been studied due to their important role in assigning the glass formation ability of materials.
Thermodynamic stability of CdMoO4 was determined
by measuring the vapor pressures of Cd and MoO3 bearing
gaseous species. Th vaporization reaction could be described as CdMoO4(s)+MoO2(s)
(n=3, 4 and 5). The vapor pressures of
the cadmium (pCd)
and trimer (p(MoO3)3)
measured in the temperature range 987≤T/K≤1111
could be expressed, respectively, as ln (pCd/Pa)
= –32643.9/T+29.460.08 and
ln(p(MoO3)3/Pa) = –32289.6/T+29.280.08. The standard molar Gibbs free
energy of formation of CdMoO4(s),
derived from the vaporization results could be expressed by the equations:
(s)0= –1002.0+0.267T14.5 kJ mol–1
(987≤T/K≤1033) and fGCdMoO4 (s)0
= –1101.9+0.363T14.4 kJ mol–1
(1044≤T/K≤1111). The standard enthalpy
of formation of CdMoO4(s)
was found to be –1015.414.5 kJ mol–1
Authors:S. Mishra, D. Tiwari, S. Prasad, R. Dubey, and Manisha Mishra
The removal behavior of amorphous aluminum hydroxide for Hg(II) ions from aqueous solutions was investigated by employing
a radiotracer technique at micro down to trace level concentrations. The batch type experiments were performed to obtain various
physico-chemical parameters, viz., effect of sorptive concentration, temperature and pH. It was observed that the increase
in sorptive concentration (from 1·10−8 to 1·10−2 mol·dm−3), temperature (from 303 to 333K) and pH (from 3.4 to 10.3) apparently favored the uptake of Hg(II) by this solid. Similarly,
the presence of anions (six fold) viz., oxalate, phosphate, glycine and EDTA also enhanced the uptake behavior of aluminum
hydroxide for Hg(II). Whereas, the added cations viz., Na+, K+, Ba2+, Sr2+, Mg2+, Cd2+ and Fe3+ more or less suppressed the removal behavior of the adsorbent. Further, the adsorption process followed the classical Freundlich
adsorption isotherm and deductions of various thermodynamic data revealed that the uptake of Hg(II) on aluminum hydroxide
followed the ion-exchange type mechanism and thermodynamically it was found to be endothermic in nature.
Authors:S. Mishra, D. Tiwari, S. Prasad, R. Dubey, and M. Mishra
The role of dead biomasses viz., mango (Mangifera indica) and neem (Azadirachta indica) bark samples are assessed in the removal behavior of, one of important fission fragments, Cs(I) from aqueous solutions employing
a radiotracer technique. The batch type studies were carried out to obtain various physico-chemical data. It is to be noted
that the increase in sorptive concentration (from 1.0·10−8 to 1.0·10−2 mol·dm−3), temperature (from 298 to 328 K) and pH (2.6 to 10.3) apparently favor the uptake of Cs(I) by these two bark samples. The
concentration dependence data obeyed Freundlich adsorption isotherm and the uptake follows first order rate law. Thermodynamic
data evaluation and desorption experiments reveal the adsorption to be irreversible and endothermic in nature proceeding through
ion-exchange and surface complexation for both dead biomasses. Both bark samples showed a fairly good radiation stability
in respect of adsorption uptake of Cs(I) when irradiated with a 300 mCi (Ra-Be) neutron source having an integral neutron
flux of ∼3.85·106 n·cm−2·s−1 and associated with a nominal γ-dose of ∼1.72 Gy·h−1.
Liquid-liquid extraction of uranium (VI) from aqueous phosphoric acid solution by triisodecylamine (Alamine 310), tri-n-butyl phosphate (TBP), di-n-pentyl sulfoxide (DPSO) and their mixtures in benzene in the range 1–10M aqueous H3PO4 shows that extraction is maximum (80%) in the higher acidity range 6–8 M. Extraction of this metal ion by bis(2,4,4-trimethylpentyl)phosphinicacid (Cyanex 301) and its mixtures studied in the range 0.2–1.0M aqueous H3PO4 is far from being quantitative. Antagonism in extraction by mixtures of extractants is observed in most of the cases. Extraction of molybdenum(VI) under identical conditions shows that it is quantitative in the lower acidity range upto 2M H3PO4. Separation of uranium(VI) from molybdenum(VI) is feasible by Alamine 310, TBP and DPSO, the order of efficiency being TBP>DPSO>Alamine 310.