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[en] Ruthenium a group VIII element in the periodic table exhibits variable oxidation states, is available in earth’s crust with an average abundance of 0.001 ppm. It has seven naturally occurring isotopes besides two long lived radioisotopes 103Ru (t1/ 2 = 40 days) and 106Ru (t1/2 = 386 days) that are primarily produced in nuclear reactors. The chemistry of this fission product is complex due to various oxidation states and tendency to form large number of coordination complexes, which interferes during reprocessing. Essentially all of the radio ruthenium encountered in the environment is the result of atmospheric nuclear weapon test and operations related to nuclear power generation. Carbon nanotubes play a significant role towards separation of radionuclides for their high surface area, hollow structures, low density, high thermal and radiation stability. This paper describes the adsorption behavior of ruthenium on Multi Walled Carbon Nanotubes (MWCNTs) from aqueous solution
[en] Uranium is of great importance as nuclear fuel, natural uranium is used in heavy water nuclear power reactors and enriched uranium is used in light water nuclear power reactors. In the thorium nuclear fuel cycle, clean-up of uranium-233 is a challenging task. Atomic vapour laser isotope separation (AVLIS) is a promising method for enrichment of 235U, as well as clean-up of 233U. But, it requires high temperature of the vapour source for higher throughput. It is, therefore, important to know thermodynamic properties of uranium vapour at higher temperature, as these have bearing on both the classical and quantum characteristics of the freely expanding vapour/collimated beam employed in AVLIS. In order to lower the temperature required for collection of product and tail as liquids, for continuous operation of the AVLIS process, it has been suggested that iron be co-evaporated with uranium, as uranium and iron form eutectic at 996 K, with a composition of 0.66 U + 0.34 Fe. So, it is important to know the thermodynamic properties of iron vapour also
[en] The equilibrium CO pressure over the condensed phase region of CeO2(s)-CeC2(s)-C(s) was determined by adopting a method termed as the dynamic effusion MS method, which involves the measurement of the CO effusing out from the sample using a quadrupole mass spectrometer, even during carbothermic reduction of the oxide. The formation of oxicarbide has been ruled out. The Gibbs energies of the reaction CeO2(s)+4C(s)=CeC2(s)+2CO(g), at various temperatures in the rang 1350-1550 K were then determined from the equilibrium CO pressures. From the Gibbs energies of the reaction, the Gibbs energy of formation of CeC2(s) at 298 K was derived. Similarly, from the data on the second and third-law enthalpies of the above reaction, the enthalpy of formation of CeC2(s) at 298 K was calculated. The recommended Gibbs energy and enthalpy of formation of CeC2(s) at 298 K are (103.0±6.0) and (120.1±11.0) kJ mol-1, respectively
[en] Owing to its desirable nuclear and mechanical properties such as good absorption cross-section for thermal neutrons (105 barns), hafnium titanate (HfTiO4) finds application as control rods for nuclear reactors. An accurate knowledge of the thermo physical properties of this material is necessary for design of control rod and for modeling its performance. Heat capacity is an important thermodynamic property that determines the temperature dependent variation of all other thermodynamic properties. Hence enthalpy increments of hafnium titanate (HfTiO4) were measured in the temperature range 803-1663 K by employing the method of inverse drop calorimetry using high temperature differential calorimeter
[en] The enthalpy and Gibbs free energy thermodynamical potentials of single walled carbon nanotubes were studied of all types (armchairs, zig-zags, chirals (n>m), and chiral (n
AB298 K or ΔGAB298 K (assembly of nanotubes from atoms) versus the chiral vector indexes n and m for any given nanotube. The equations show a good level of accuracy in predicting thermodynamic potentials for practical applications
[en] Highlights: ► Thermodynamic properties depend on the sizes of reactant in nanosystems. ► The equilibrium constant is also correlated to the sizes of reactant. ► With the sizes of reactant decreasing. ► Gibbs function, enthalpy and entropy decrease but the equilibrium constant increase. - Abstract: Thermodynamic properties and equilibrium constant of reaction in nanosystems were analyzed theoretically. The effects of sizes of nano-CuO on thermodynamic properties and equilibrium constant were studied using the reaction of nano-copper oxide and sodium bisulfate as a system. The experimental results indicate that with the sizes of reactant decreasing, the molar Gibbs free energy (ΔrGm), the molar enthalpy (ΔrHm) and the molar entropy (ΔrSm) decrease, but the equilibrium constant (K) increases and there are linear trends between the reciprocal of sizes for nano-CuO and the values of ΔrGm, ΔrHm, ΔrSm and Ln K, which are in agreement with the theoretical analysis.
[en] NiHA stability constants (β values) have been derived at different temperatures from the amounts of nickel (Ni2+) and nickel humate (NiHA), determined to be present, in equilibrated nickel humic acid mixtures at 4 C, 20 C, 40 C, 60 C and 80 C. The constants were deduced using (i) a simple Scatchard plot, (ii) a metal-humic acid charge neutralisation model and (iii) an electrostatic/discrete site complexation model as implemented in the CHESS geochemical speciation code. The derived values depended on whether bulk solution (Scatchard and Charge Neutralisation Approaches) or humic surface metal concentrations (Electrostatic Approach) were employed in the calculations. The Scatchard and Charge Neutralisation approaches were found to be mathematically equivalent. The differently derived constants and their temperature dependencies have been used to calculate corresponding thermodynamic ΔH, ΔG and ΔS values. The values obtained are compared and features of thermodynamic significance discussed. (orig.)
[en] Thermometric titrations performed in suitable conditions permit the determination of the enthalpic and entropic parts of the standard transfer-free enthalpy of a particular 5-formyl-1,2-dithiole-3-thione from water into n-octanol. It may be inferred from this determination that the far too high water/n-octanol log P values of 5-acyl-1,2-dithiole-3-thiones originate in an entropic effect which is in agreement with the hypothesis that these derivatives are more solvated in water than expected and hence with the hypothesis that during partitioning between the two phases, more molecules of water than expected are released from the solvated solute in the aqueous phase. The family of 1,2-dithiole-3-thiones is of growing importance in pharmacology
[en] The Gibbs energy, enthalpy and entropy of higher lanthanum silicide formation has been determined by means of electromotive force measurements of concentrational galvanic cells at 960-1050 K
[en] Using the polyhedral units model of Hazen and employing a method of least-squares, the contribution of nineteen constituent units to the free energy and fifteen units to the enthalpy, at 298 K and 1 bar of pressure, have been calculated for mineral phosphates. The contribution of these constituent units to the free energy at higher temperatures has also been calculated. From these data we can estimate the thermodynamic properties of phosphates by summing the contribution of the distinct units, with more accuracy than the methods published up until now. (Author) 36 refs.