Recovery of cobalt metal powder from el BOLEO plant using reduction processes

At optimized conditions of hydrazine/Co molar ratio of 0.5:1, 70 °C, 7 M NaOH, over 98% Co could be recovered as 99.8% pure Co metal powder, which could be subsequently briquetted to buttons for easier handling. Cementing Co powder using Mn at various Mn/Co ratios show losses of Mn and passivation causing low Co recovery. At > 30% excess, > 95% of Co is recovered as 93% pure Co powder. During processing Zn, Fe, Mn impurities were removed as sulphide, which also caused 10% of the available Co to co-precipitate as Co sulphide containing 13.5% ZnS. Roasting of this material at > 1300 °C produced > 98% grade CoO-Co3O4, which can be recycled to the leaching stage.