Separation and concentration of rare earth elements from wastewater using electrodialysis technology

Rare earth elements (REEs) including Scandium (Sc) are critical raw materials which are greatly needed in the advancement of many modern technologies. Due to the problems associated with the primary extraction of mining ores, the procurement of Sc and REEs from the secondary resources are currently explored adopting the principle of sustainability and circular economy. Herein, for the first time, the Electrodialysis (ED) technology based on electrochemical membrane separation process is successfully applied to separate and concentrate REEs from the diluted aqueous system. The overall performance of ED process in the recovery of Sc³⁺ ions from the wastewater was assessed by applied current, voltage, feed concentration, feed pH, co-ion competition and the overall energy consumption of the process. The REE recovery using the ED process was subjected to systematic investigations using both chronopotentiometric and chronoamperometric analyses. The results showed that ED process could be very promising in the recovery of Sc³⁺ ions (~99.52% removal) from the diluted wastewater, consuming the energy of only 0.26 kWh/m³ when operated at constant voltage mode (Sc³⁺ concentration of 20 ppm, pH 4, 1 h).