Collaborative extraction of valuable components from saprolitic laterite ore through two-stage nitric acid leaching

Saprolitic laterite ore (SLO) is an important Ni resource that also contains high Mg and a small amount of Sc, but traditional extraction techniques cannot achieve the comprehensive utilization of valuable components, especially Mg and Sc. In this work, a new process was proposed to treat SLO through the application of an HNO3 medium. First, E-pH analysis showed that serpentine and part of iron oxide are easily destroyed, and Ni and Co embedded in silicate and Fe-bearing minerals can be also leached. Subsequently, Ni, Mg, Co, and Sc can be efficiently extracted under the HNO3 concentration of 240 g/L, 90 degrees C, L/S of 5:1, 2 h, and 200 r/min. Relevant characterization confirmed that serpentine and goethite were almost completely dissolved after leaching. However, magnetite and its alteration intermediates have relatively stable properties and cannot be destroyed. To reduce acid consumption, the leach liquor was supplemented with HNO3 for two-stage leaching. Efficient extraction of valuable metals can be achieved again with the supplemented HNO3 concentration of 192 g/L. A two-stage leaching process can save 120 kg HNO3/t-ore. Finally, a technical route including two-stage HNO3 leaching, adding MgO to adjust pH, and pyrolysis of Mg(NO3)2 to regenerate HNO3 and MgO was suggested.