ABSTRACT:

Precipitation of manganese from the SO2-roast leach ammoniacal ammonium sulphate solution bearing both high and low manganese content was carried out in a stainless steel reactor fitted with a turbo grid. Air/O2 was used to precipitate Mn as MnO2. There was adsorption loss of cobalt from solution. There was precipitation of 57.2 - 99.96% Mn with loss of 3% Cu, 3.5% Ni and 2.9% Co The data were fitted to Freundlich and Langmuir adsorption isotherms.

INTRODUCTION

Ores, concentrates and by-products containing manganese, copper, nickel and cobalt are directly subjected to ammoniacal leaching (Fuerstenau- Han,1983; Hubred, 1980) or after pretreatment (Caron, 1950; Siemens- Corrick, 1977). Precipitation of Mn (Nathsarma-Sarma, 1993) from the Fe-free solution with K2S2O8 equivalent to four times its stoichiometric quantity and heating it at 85–90°C for one hour on a water bath lead to quantitative precipitation of Mn with 27% loss of cobalt. Precipitation of manganese as MnO2 from the zinc electrolyte solution bearing manganese and cobalt (Can. Patent, 1957; US patent, 1978) with K2S2O8 was also carried out in a pilot plant scale in South Africa. Mn(II) was precipitated (Ying-Zhu- Bao-Liu-Wang-Zhang and Youse,1966) from a chloride solution bearing 11.8 kg/m3 Mn, 105.4 kg/m3 Co, and 0.29 kg/m3 Mg with KMnO4 at KMnO4 to Mn mole ratio of 1.12 leading to 99% precipitation of Mn. Precipitation of manganese (Zhang-Singh and Muir, 2002) from an acidic solution bearing Fe, Mn, Co and Ni was carried out with the mixtures of SO2 and O2 in the in the pH range 1–6 and temperature range 25–80oC where oxidation of Mn (II) was first order with respect to SO2 up to the partial pressure of SO2 up to 5.7. The rate of Mn oxidation was slow at pH < 3 but increased rapidly at pH > 4.

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