Spinel ferrite transformation for enhanced upgrading nickel grade in laterite ore of various types

Upgrading nickel grade in low-grade nickeliferous laterite ores before metallurgical extraction process is of utmost importance. However, most of nickel exists mainly in the form of isomorphism in serpentine or goethite, resulting in difficulty in upgrading of nickel by physical separation methods. In this paper, spinel ferrite transformation for enhanced upgrading nickel grade in laterite ore of various types was proposed. The mineral phase transformation and migration of valuable metals for various laterite ores during calcination process was investigated, as well the influences of mineral phases and chemical compositions on magnetic properties, separation efficiency, and nickel contents in separated laterite ore. The results show that spinel nickel ferrite mainly composed of nickel oxide and iron oxide could be completely formed after calcined at 800, 1000 and 900 degrees C for limonite, saprolite and transition laterite ore, respectively. With the increase of calcination temperature, the crystallinity and saturation magnetization Ms value of as-calcined samples become improved, leading to increased nickel recovery, while the nickel content in magnetic fraction is first increased and then slightly decreased. Under the optimum calcination conditions, the nickel recovery for limonite, saprolite and transition laterite ore could reach 68.5%, 68.9% and 67.3%, respectively, while the nickel contents in magnetic fraction are 3.01%, 3.23% and 3.15% with increasing by 1.82, 2.27 and 2.11 times, respectively. This paper could provide theoretical basis and technology support for enhanced upgrading of valuable metals from complex associated mineral resources.