Microwave-assisted leaching of olivine: Investigation of leaching characteristics and kinetics of Mg, Si, Fe, Co, and Ni
Sepehr Ghaderi, Wencai Zhang
Abstract
Olivine, a silicate ultramafic rock, has been a promising primary resource of nickel and cobalt for the past years. Microwave-assisted leaching of selected elements, namely magnesium (Mg), silicon (Si), iron (Fe), cobalt (Co), and nickel (Ni) from olivine was compared with the conventional leaching method. Also, the effects of acid type, sulfuric acid concentration, solid-to-liquid (S/L) ratio, reaction time, and reaction temperature were investigated. Approximately 100 % of selected elements were extracted from olivine under suitable conditions of 0.5 M sulfuric acid concentration, 2.5 % S/L ratio, 20 min, and 160 °C. Microwave-assisted leaching enabled the leaching process to be conducted with high efficiency, with lower acid consumption within a very short time. Leaching kinetics modeling suggested that the microwave-assisted leaching of selected elements is governed by the Avrami model, while the surface reaction shrinking core model governs the conventional leaching kinetics. The morphology study of solid residues resulting from microwave-assisted leaching experiments indicated that the microfractures and cracks facilitate the leaching efficiency of selected elements by providing a higher reaction solid–liquid interface. This study reveals valuable insights into the leaching characteristics and kinetics of major and critical elements from olivine using microwave-assisted leaching.