Extracting light rare earth elements by applying electric field assisted mining technique

Abstract

Light rare earth elements are critical raw materials that present several applications, including the use in the manufacturing of high-tech products and green energy production systems. Considering their criticality, there is a need to increase the production of these commodities. The electric field assisted mining is an eco-friendly technique that uses the electrokinetic phenomena to remove metallic species from soils. Considering that electric field strength and electrolyte concentration are key factors that directly influence the species extraction via the electrokinetic process, the aim of the present work was to evaluate the effect of these variables on the removal of the cerium, lanthanum, and neodymium ions. To that end, a full factorial design was conducted to assist in statistical analysis, and response surfaces were built aiming to analyze the rare earths removal. The results showed that the main effects of electric field strength and electrolyte concentration presented individually a positive effect on the removal of the species. In addition, the neodymium removal also presented the interaction effect between the variables in the analysis. The experiment that showed the best performance was conducted using acetic acid at 0.1 mol L−1 and an electric field of 1.0 V cm−1, resulting in a mining efficiency of 78.5% of Ce4+, 47.7% of La3+ and 35.1% of Nd3+, with an energy consumption of 6.5 W h after 240 h of experiment. Regarding these results, and also taking into account the use of weak and organic acid and mild experiments conditions, electric field assisted mining presents itself as a feasible and eco-friendly technique to remove rare earth elements from soils.