Nickel laterite Part 1 – microstructure and phase characterisations during reduction roasting and leaching

Abstract

Detailed microstructure and phase characterisations of processed nickel laterite ore feed, reduced ore and leached ore have been carried out using scanning electron microscope, synchrotron X-ray powder diffraction and electron probe X-ray microanalysis as a part of study aimed to increase Ni recovery from the laterite ores. The majority of the nickel in the ore feed were found to be associated with fine grained goethite (Fe rich matrix of limonite composite) and serpentine particles. These phases were transformed to magnetite and olivine respectively upon reduction roasting. Nanosize metallic particles were also observed on the free surface of limonite composite particles following reduction roasting. Upon leaching, .90% of the nickel in the Fe rich matrix was leached out, while ,50% was removed from the olivine and its composites. The characterisation results from this study were used to assist the analysis of thermodynamic and phase changes during reduction roasting and leaching described in Part 2 of the paper.

The electrochemistry of the leaching reactions in the Caron process II. Cathodic processes

“…The cathodic limiting current of about -3 mA cm -2 is consistent with the results in Figure 2 and Figure 7 as being due to the reduction of cobalt(III) to cobalt(II). The curves at potentials below -0.9 V are similar to those for the solution containing nickel, with the HER occurring initially on a platinum surface but being replaced by that on a cobalt surface following deposition of cobalt by the reverse of the reaction Co + 5NH 3 → Co(NH 3 ) 5 2+ + 2e -The formal reduction potential for this reaction is -0.89 V under the conditions of this experiment. The lower overpotential for the oxidation of the deposited cobalt and the lack of noticeable passivation (as evidenced by the appearance of peaks for the HER in subsequent scans and the greater anodic charge during stripping) are consistent with previously published data on the behaviour of nickel and cobalt [6].…”

“…It remains a robust, technically advanced process for the treatment of lateritic ores [2]. Much of the nickel and cobalt are alloyed with a portion of iron during the roasting, and hence the chemistry of the extraction of the nickel and cobalt is linked closely with the dissolution and precipitation characteristics of iron [3][4][5].…”

Sulfides Formation in Carbothermic Reduction of Saprolitic Nickel Laterite Ore Using Low-Rank Coals and Additives: A Thermodynamic Simulation Analysis

“…Nickeliferous laterite ore has complex composition and mineralogy; and it contains different metals such as iron, magnesium, aluminum, silicon, nickel, cobalt, manganese, and others. Comprehensive microstructure characterizations carried out previously by Rhamdhani et al [4] show that typical lateritic ore contain composite and single-phase particles of different sizes having structure of composite mixture, fine grain mixture, intergrowth, vein-like/plate-like, porous, and dense, depending on the degree of weathering. This complex microstructure and the broad spectrum of chemical alteration due to weathering effect results in the difficulties in the beneficiation process of the ore.…”

Production of Ferronickel Concentrate from Low-Grade Nickel Laterite Ore by Non-Melting Reduction Magnetic Separation Process

“…It can be seen from the XRD pattern that the main phase of the roasting product is forsterite. The existence of the phase is mainly attributed to the following: (1) forsterite is formed by recrystallization of silicate in minerals [20]; (2) serpentine is transformed into forsterite during roasting (Equations (12) and (13)) [21]. No matter how the forsterite is formed, Ni and Fe are released during the phase transformation, which is beneficial to reduction.…”

“…(2) serpentine is transformed into forsterite during roasting (Equations (12) and (13)) [21]. No matter how the forsterite is formed, Ni and Fe are released during the phase transformation, which is beneficial to reduction.…”