Manganese precipitation kinetics and cobalt adsorption on MnO2 from the ammoniacal ammonium sulfate leach liquor of Indian Ocean manganese nodule

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.

► Highest precipitation of Mn was achieved with air flow rate of 30 L/min.
► Mn precipitation and Co adsorption obeyed the first order kinetics.
► Loss of Co was due to adsorption on MnO2.
► Co adsorption on MnO2 obeys Freundlich and Langmuir adsorption law.