Rare Earth Elements Partition and Recovery During Electrodialytic Treatment of Coal Fly Ash

Rare earth elements (REE) recovery from waste (end-of-line, reusable, recyclable, etc.) should become an essential stream of REE for current demands. Methods to achieve this recovery are then paramount. This study uses the electrodialytic remediation (EDR) as an REE extraction method from coal fly ashes. We used different chemicals to assist REE extraction during EDR: distilled water, 0.01 mol l⁻¹ NaNO3, 0.4 mol l⁻¹ Sodium acetate in 1.0 mol l⁻¹ Acetic acid, and 0.5 mol l⁻¹ Citric acid. Citric acid achieved the highest REE extraction/recovery from the four studied solutions: up to 40%. This represents a total recovery of 148 g REE from 1 ton of coal ashes. The citric acid experiment also proved to be energy efficient, using 70 Wh per 100 g of treated coal ash. The acidic environment provided by the citric acid supplies higher REE migration rates towards the cathode. Once at the cathode compartment, REEs then precipitate at the cathode complexed as Ca- and P-bearing minerals.