Recovery of rare earth elements from ion-adsorption deposits using electro kinetic technology: A comparative study on leaching agents

Ion-adsorption rare earth deposits are crucial sources of heavy rare earth elements. Conventional ammonium-salt leaching techniques have resulted in severe environmental impacts. Electrokinetic mining technology has emerged as a potential solution that can enhance recovery efficiency. However, persistent issues associated with ammonium salts and the influence of electric fields on rare earth elements extraction from ion-adsorption rare earth deposits with alternative leaching agents remain unexplored. In addition, the electrokinetic behavior and mechanisms of rare earth ions and various ions in weathering crusts in an electric field have not been studied. Thus, we report a comparative study of rare earth elements recovery using electrokinetic mining technology with three leaching agents. The results demonstrate that the electrokinetic mining efficiency is enhanced by using magnesium sulfate and ammonium sulfate; however, hindered by sodium sulfate. These differences arise from the diversities in adsorption amounts, and transport characteristics of the leaching cations in soil. Surprisingly, electrokinetic mining technology exhibits superior mining efficiency in high-density soils, contrasting with conventional leaching techniques. Our findings indicate that electromigration, electroosmosis, and electrolysis mechanisms collectively influence the mining process. Remarkably, electrokinetic mining technology achieves a significant rare earth element recovery efficiency of 90 % using magnesium sulfate synergically promoted by the voltage and leaching agent concentration. The findings of this study are expected to provide valuable insights into rare earth elements transport and exchange behavior in an electric field with various leaching agents, thereby contributing to the advancement of sustainable rare earth elements mining practices.