Effect of Sodium Carbonate on Phase Transformation of High-Magnesium Laterite Ore

Abstract

The phase transformation of high-magnesium laterite ore were investigated during the reduction roasting process. In the absence of sodium carbonate [Na₂CO₃], the X-ray diffraction results indicate that the [Fe Ni] alloy existed in ore in the form of taenite. The taenite particles is fine and the size is approximately 30–40 nm, which indicate that the nickel and iron are not migrated and aggregated during the non-smelting reduction roasting process. In the presence of sodium carbonate, the intensity of [Fe Ni] alloy phase increases; the taenite diffraction peaks disappears, corresponding to the appearance of kamacite. The results of SEM images show that the [Fe Ni] alloy particle size has a significant increase with the addition of Na₂CO₃. Based on the theoretical analysis, the pivotal role of Na₂CO₃ may be mainly attributed to the Na⁺, which could infiltrate into the crystal lattice of FeO, leading to the lattice distortion. Furthermore, the sodium carbonate would be decomposed at high temperature, and the generated CO₂ could promote the Boudouard reaction which produced the CO to enhance the reduction of metallic oxides within ore.