Enhancing Rare Earth Element Recovery from Coal Ash Using High-Voltage Electrical Pulses and Citric Acid Leaching

• Published in: Minerals (Basel) Vol. 14; no. 7; p. 693
• Main Authors: Ketegenov, Tlek, Kamunur, Kaster, Mussapyrova, Lyazzat, Batkal, Aisulu, Nadirov, Rashid
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.07.2024
• Subjects: Acid leaching; Ash; Cavitation; Cerium; Chemical reactions; Citric acid; citric acid leaching; Coal; coal ash; Coal-fired power plants; Controlled conditions; Efficiency; Fly ash; High voltages; high-voltage electrical pulses; Hydrochloric acid; Kinetics; Lanthanum; Leaching; leaching kinetics; Minerals; Optimization; Rare earth elements; Recovery; Sulfuric acid; Temperature; Voltage; Yttrium; Kazakhstan; Russia
• ISSN: 2075-163X; 2075-163X
• DOI: 10.3390/min14070693

The study investigates the application of high-voltage electrical pulses (HVEP) as a pretreatment to enhance the leaching efficiency of rare earth elements (REE) from coal ash (CA) produced from the combustion of Ekibastuz Basin coal in Almaty, Kazakhstan. HVEP treatment was applied to the finest (<40 µm) non-magnetic fraction of CA under controlled conditions, optimizing discharge current, voltage, and treatment duration. Leaching experiments with 1 M citric acid at various solid-to-liquid ratios, temperatures, and durations were conducted on both treated and untreated samples. Results indicated that HVEP-treated CA significantly improved REE recovery rates compared to untreated samples, with optimal conditions achieving 74% cerium, 79% yttrium, and 77% lanthanum recovery. The leaching of untreated CA under the specified conditions allowed no more than 28% REE to be extracted into the solution. The leaching process was found to follow first-order kinetics, with the chemical reaction of metal dissolution being the rate-limiting step.