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Abstract An array of eight CsI(Tl) detectors has been set up to measure the light charged particles in nuclear reactions using heavy ions from the Pelletron Linac Facility, Mumbai. The energy response of CsI(Tl) detector to α -particles from 5 to 40 MeV is measured using radioactive sources and the 12C(12C, α) reaction populating discrete states in 20Ne. The energy non-linearity and the count rate effect on the pulse shape discrimination property have also been measured and observed the deterioration of pulse shape discrimination with higher count rate. [ABSTRACT FROM AUTHOR]

Abstract Spent hydrodesulphurization (HDS) catalysts containing valuable Mo and Ni ions are potential source for the recovery of Mo and Ni from the point of commercial, environmental and conservation of natural mineral resources. In the present study, oxidative roasting of spent HDS catalyst followed by ammonia leaching results in the leach liquor with about 15.3 g/L Mo (~85% recovery), ~125 g/L (NH 4) 2 SO 4 and ~0.9 g/L Ni as impurity. Therefore Ni separation from this ammoniacal molybdate leach liquor is essentially the first step to obtain high pure molybdate and ammonium sulfate solution. In this study, separation of nickel from ammoniacal molybdate leach liquor was reported using commercial chelating iminodiacetate resin, Lewatit TP207 by batch and column methods. Optimization of process parameters include equilibration time, acidity of leach liquor, aqueous flow rate, metal concentration, loading capacity of resin for Ni during sorption of Ni, desorption of nickel from loaded resin and stability and reuse of resin in continuous column experiments. Feed leach liquor of pH >8.0 is important to achieve clear separation of Ni from Mo. Loading capacity of resin and break through curves are optimized to achieve <10 mg/L Ni in purified Mo leach liquor and further processing results in high grade ammonium octamolybdate (AOM) and ammonium sulfate crystals. Finally, a process flow sheet for the complete separation and recovery of Ni, Mo and ammonium sulphate with material balance from ammoniacal molybdate leach liquor of spent HDS catalyst was demonstrated for possible industrial application. Highlights • Selective separation of Ni from ammoniacal molybdate leach liquor by Lewatit TP207 • Quantitative Ni recovery was achieved using continuous column experiment • Recovery of high pure AOM and (NH 4) 2 SO 4 was achieved • Regeneration & reuse of resin for number of cycles showed consistent performance • Environmental friendly processing scheme with material balance demonstrated [ABSTRACT FROM AUTHOR]

Spent nickel-tungsten catalyst generated from hydrotreating petroleum industry always contains molybdenum about 0.1–2% as an impurity. Separation of Mo from spent Ni-W catalyst leach solutions is a critical step to produce high pure tungsten products like ammonium paratungstate (APT) and tungsten trioxide (WO 3 ) for catalyst and tools applications. Though Mo and W have chemically similar properties but it is possible to exploit separation of Mo from W by modifying the aqueous phase species. In the present paper, alkaline leach liquor with a composition of 0.72 g/L Mo and 18 g/L W was taken. Selective separation of Mo as its thiocomplex from W was examined by Aliquat 336, a quaternary ammonium compound. Experimental parameters such as extraction pH, concentration of extractant and metal for extraction and selection of reagent and concentration for stripping were optimized to obtain maximum separation of Mo. Variation of extractant concentration indicated extracted Mo species as (R 3 CH 3 N) 2 MoS 4 . The McCabe-Thiele plots indicated that 2 and 3-counter-current stages are necessary at O:A ratio of 1:1 and 3:1 for quantitative extraction and stripping of molybdenum, respectively. A pilot run for 330 h was operated with 3-stages of extraction, 1-stage of scrubbing, 3-stages of stripping and one stage of washing based on the equilibrium data to verify the performance of Mo separation from W from commercial point of view. [ABSTRACT FROM AUTHOR]

Abstract: Precipitation of manganese from the SO2-roast leach ammoniacal ammonium sulfate solution bearing both high and low concentrations of manganese in the presence of copper, cobalt and nickel ions was carried out in a stainless steel reactor fitted with a turbo grid. Air/O2 was used to precipitate Mn as MnO2 from the solution. There was adsorption loss of cobalt from the solution. Precipitation of manganese from the solution was 57.2–99.9%. The maximum adsorption loss of Co was 22.1%. The precipitation of Mn and adsorption loss of cobalt from the solution followed the first order kinetics. The rate constants for the precipitation of manganese and loss of cobalt were evaluated and the experimental data were fitted to Freundlich and Langmuir adsorption isotherms. [Copyright &y& Elsevier]

Molybdenum is often associated with nickel-tungsten based spent HDS catalyst and must be removed from tungstate solution to obtain commercially acceptable tungsten products. In order to address this problem, a different approach has been proposed in the present work. A two step process based on selective thionization of Mo using Na 2 S at alkaline condition followed by W precipitation as calcium tungstate (CT) using lime (Ca(OH) 2) was studied. Various operating parameters were tested and optimum conditions for Mo thionization and W precipitation were developed. The CT produced by the conventional process was used as a reference to check the improvement in the proposed process with respect to Mo impurity. Under the optimum conditions, 92.7% Mo was rejected to the CT filtrate and 99.7% W converted to CT. The CT obtained from the proposed process contained 0.53% Mo, which was much less as compared to the CT obtained from the conventional process having 2.5% Mo using the same leach solution. High-grade ammonium paratungstate (APT) containing <100 ppm Mo was obtained by treating the CT, which can be used for the tools industry and other applications. • High grade CT preparation from sodium tungstate leach liquor was proposed. • Mo was separated from varying Mo bearing W leach liquors. • Selective thionisation of Mo is the key step to achieve high grade APT from the generated CT. • High grade APT containing <100 ppm Mo was obtained by treating the CT. • The process is simple, cost effective and can be applied industrially. [ABSTRACT FROM AUTHOR]

Abstract: Exclusive measurements of prompt γ-rays from the heavy-residues with various light charged particles in the 7Li+ 198Pt system, at an energy near the Coulomb barrier () are reported. Recent dynamic classical trajectory calculations, constrained by the measured fusion, α- and t-capture cross-sections have been used to explain the excitation energy dependence of the residue cross-sections. These calculations distinctly illustrate a two-step process, breakup followed by fusion, in case of the capture of t and α clusters; whereas for and configurations, massive transfer is inferred to be the dominant mechanism. The present work clearly demonstrates the role played by the cluster structures of 7Li in understanding the reaction dynamics at energies around the Coulomb barrier. [Copyright &y& Elsevier]