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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]