Abstract
| We present a carbonation-assisted flotation method for nickel (Ni) separation from low-grade ultramafic ores. The high process economics of conventional flotation of low-grade ultramafic ores makes Ni unrecoverable on an industrial scale. Based on the fundamentals of CO2 sequestration in minerals, we carbonated a low-grade serpentine (lizardite) ore specimen under the conditions (185 °C, 15 MPa, 24 h) and attained conversion of serpentine to magnesite of 22 and 16% in the presence and absence of inorganic salts, respectively. Rhombohedral structures on carbonated particles detected using scanning electron microscopy suggested the formation of magnesite. We also found that Ni-Fe existed as sulfides, confirmed by elemental mapping micrographs, and did not leach out as Ni2+ and Fe2+, confirmed through the carbonation supernatant analysis. Here, we introduce Denver cell froth flotation experiments after carbonation, which showed that the carbonated ore in the presence of inorganic salts had 29% and 0.15 wt.%, respectively, higher Ni recovery and grade than the uncarbonated ore. This study is the first to successfully show that the carbonation of serpentine containing nickel-bearing pentlandite, leads to magnesite formation, does not lead to the dissolution of nickel sulphide, and enhances the nickel separation efficiency during froth-flotation. This study paves the path forward for the integration of mineral carbonation in the processing of low-grade ultramafic nickel ores. |
Keywords
mineral carbonation, carbon capture storage and utilization, industrial CO2 emissions, nickel sulphide processing, low-grade ultramafic ore, froth-flotation, sustainable production of critical minerals
