Intensified extraction of rare earth elements from coal fly ash

BACKGROUND: The high demand for coal-based energy leads to the production of a massive amount of coal fly ash (CFA). Owing to the content of rare earth elements (REEs), CFA is regarded as one of the promising secondary sources of REEs. The corrent study utilized two intensified extraction methods, subcritical water extraction (SWE) and microwave assisted extraction (MAE), in the recovery of REEs, including yttrium (Y) and samarium (Sm), from CFA sample. RESULTS: The effects of acid concentration, temperature, and solid to liquid ratio (S/L), and reaction time on leaching efficiency were investigated. Total of 80.32% of Y and 68% of Sm were leached out using SWE at 1.0 N HCl, S/L of 5 g/L, 150 degrees C for 5 min. Meanwhile, MAE yielded leaching efficiency of 71.99% of Y and 54.48% of Sm at 2.0 N HCl, S/L of 2.5 g/L, 150 degrees C for 5 min. Both methods performed better than conventional method. CONCLUSIONS: From comparisons, SWE showed advantages of higher leaching efficiency at lower acid concentration, while MAE was more rapid and more energy efficient for REEs recovery from CFA. (c) 2023 Society of Chemical Industry (SCI).