Quantifying electrokinetic recovery of rare earth elements via electric charge modeling

Abstract

Electrokinetic mining (EKM) offers a sustainable pathway for extracting rare earth elements (REEs) from ion-adsorption deposits, yet the governing recovery mechanisms remain poorly understood. Here, we integrate response surface methodology (RSM) with controlled electrokinetic experiments to identify the dominant physical parameters governing REE recovery, establishing quantitative relationships between key parameters and recovery efficiency. Using mixed electrolyte systems, we demonstrate that cation pairing and their ratios work synergistically to enhance REE recovery through improved ion exchange kinetics and increased soil conductivity. We identify the total electric charge (QEC) as a universal predictor of recovery efficiency across conditions. Embedding QEC into the RSM framework yields a robust predictive model for parameter selection, validated through experiments, achieving 95% REE recovery under optimized conditions (0.10 mol l−1 MgSO4 and 0.03 mol l−1 (NH4)2SO4 under 0.4 V cm−1 electric field). These findings provide mechanistic insights and a quantitative framework for advancing EKM technology toward scalable, sustainable REE recovery.