Extraction of rare earth elements via electric field assisted mining applying deep eutectic solvents

Rare earth elements play an important role in our society, as they are used in green energy technologies. However, they are considered critical raw materials. For this reason, there is a concern for obtaining alternative and complementary sources for conventional mining. In light of this view, electric field assisted mining arises as a technique to extract species from soils using green electrolytes to help in the extraction of metals. The aim of this paper was to evaluate the effect of different types of biodegradable electrolytes, including the use of deep eutectic solvents, in the electromining process. Six experiments were conducted applying an electric field of 1.0 V cm⁻¹, and all electrolytes were used at a concentration of 0.1 mol L⁻¹. The results showed that different electrolytes achieved different selectivities. The maximum efficiency using acetic acid resulted in 69.1% of Ce⁴⁺, citric acid removed 62.3% of La³⁺, and oxalic acid extracted 21.5% of La³⁺. The electromining efficiencies using deep eutectic solvents presented minor results. Therefore, considering the biodegradability and selectivity of the organic acids used, electromining showed to be a promising eco-friendly alternative for preferential extraction of metal species from soils.