A comprehensive study on the leaching characteristics and mechanisms of nickel and cobalt from olivine

In the last decades, there has been a growing demand for critical metals such as nickel (Ni) and cobalt (Co). Olivine, an orthosilicate mineral containing Ni and Co, presents a viable primary source for these metals. This study investigates the leaching behavior of selected elements, namely magnesium (Mg), silicon (Si), iron (Fe), Ni, and Co, from olivine using hydrochloric acid (HCl) and the impact of different factors. Characterization experiments indicated that Ni and Co were distributed throughout the olivine particles, being substitutes for Mg or Fe in the olivine crystal lattice. Based on the results, the favorable leaching conditions were t = 6 h, T=75 °C, solid-to-liquid ratio = 5 %, and [HCl] = 1 M, leading to 89.9 % and 90.8 % leaching efficiency for Ni and Co, respectively. Additionally, based on the shrinking particle model, the leaching kinetics of Ni and Co consisted of two distinct stages. During the initial 10 min, both film diffusion and chemical reaction controlled the process, whereas beyond this point, only the chemical reaction governed the leaching. Apparent activation energy values and morphological analysis of the solid residues confirmed the findings relevant to the leaching kinetics. This research provides valuable insights into the leaching kinetics of Ni and Co and the characteristics of solid residues, enhancing our understanding of the leaching process of olivine.