Fluorite enhanced magnesium recovery from serpentine tailings: Kinetics and reaction mechanisms

• DOI: 10.1016/j.hydromet.2021.105571
• Publication Date: 2021-02-17T11:40:42Z
• Authors: Xiangyu Peng; Wengang Liu; Wenbao Liu; Liang Zhao; Naixu Zhang; Xiaowei Gu; Shijie Zhou
• Keywords: Fluorite; Hydrometallurgy

Abstract Assisted reagents are commonly introduced into acid leaching systems to improve metal recovery. In this work, fluorite was employed to accelerate magnesium (Mg) dissolution from serpentine tailings, and the dissolution mechanism was investigated by leaching experiments, kinetics equations and reaction analyses. The effects of fluorite powder dosage, particle size, reaction temperature, sulfuric acid concentration, and agitation speed on the efficiency of magnesium leaching were comprehensively studied. The results showed that the Mg leaching efficiency increased 36.42% after adding fluorite, reaching 93.69%. A shrinking-core model could be applied to adequately describe the leaching kinetics, and the Mg dissolution was controlled by the mixing rate with a calculated apparent activation energy of 38.698 kJ·mol−1. In addition, a kinetics equation describing the leaching process was established as follows: 1/3ln(1-x)-1 + (1-x)-1/3 = 70.372P-1.071C3.17S0.497e-38,698.968/RTt. Introducing the fluorite powder markedly decreased the ∆GΘ of serpentine disintegration process; these phenomena was attributed to the complexation of F− (fluorite) with Si4+ (serpentine). Therefore, this paper proposed an effective and inexpensive reagent for application in acid leaching processes.