3.3.3. Recovery of MnCO3 from PLS-2 Solution

Using the same principle, iron precipitation assays were carried out with 1.5 SMR of H2O2 for the oxidation of Fe2<sup>+</sup> ions to Fe3<sup>+</sup> at pH = 4 and ambient temperature. Within this context, nearly 99.9% of Fe in PLS-2 was precipitated. A concentration of 2754 mg Fe/L was recorded in PLS-2 and a concentration of 2.33 mg Fe/L was measured after Fe removal (Table 5). In this step, the concentration

of Co remained stable, while all Cu was removed and the concentration of Ni decreased from 48.4 to 24.1 mg/L.

To obtain a pure manganese solution, zinc precipitation was achieved by adding Na2S (2 SMR of Na2S at pH 4–5). Under these conditions, up to 100% of zinc was precipitated (Table 5) and the obtained ZnS could be added to the first leaching stage for PLS-1 rich in Zn.

The precipitation of MnCO3 was achieved by the addition of Na2CO3. The quantity of Na2CO3 was calculated for 1 SMR, with pH 4.5–5.0 and at ambient temperature. After rinsing, the collected MnCO3 had a purity of 95%.
