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Abstract  

Dissolution effect on recoil128I retention in the form of IO 4 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.

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Abstract  

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 (T k) and the residual entropy (ΔS R) of these materials have also been studied due to their important role in assigning the glass formation ability of materials.

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Abstract  

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.

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Abstract  

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.

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Abstract  

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) =Cd(g)+2/n(MoO3)n (n=3, 4 and 5). The vapor pressures of the cadmium (p Cd) and trimer (p (MoO3)3) measured in the temperature range 987≤T/K≤1111 could be expressed, respectively, as ln (p Cd/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: f G CdMoO4 (s) 0= –1002.0+0.267T14.5 kJ mol–1 (987≤T/K≤1033) and f G CdMoO4 (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 .

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Inorganic particulates in removal of toxic heavy metal ions

Part X: Removal behavior of aluminum hydroxide for Hg(II): A radiotracer study

Journal of Radioanalytical and Nuclear Chemistry
Authors: S. Mishra, D. Tiwari, S. Prasad, R. Dubey, and Manisha Mishra

Abstract  

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.

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Abstract  

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.

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Field experiments were carried out for 3 years to assess the efficacy of organic manures (Sesbania, Leucaena, cowpea, mungbean, wheat straw and FYM) in enhancing the productivity of rice and in supplying Fe. Green manuring with Sesbania gave the highest rice yield, whereas the lowest yield was recorded with wheat straw incorporation. The concentration and uptake of Fe by rice was significantly higher with organic manures. The Fe status of the soil after 3 crops of rice declined from the initial value, but the decline was least with FYM, followed by green manures. The application of organic manures is a good source for a sustained supply of Fe in soil.

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