Recovery of Rare-Earth Elements from Brazilian Ion-Adsorption Clay: A Preliminary Study

Abstract

Ion-adsorption clays (IAC) are alumino-silicate ores, considered an essential source of heavy rare-earth elements (REE). With the increasing discovery and exploitation of IAC deposits, the present work sought to evaluate different methods of solubilization of REE through the use of different concentrations of inorganic acids (H2SO4, HCl, and HNO3), as well as different concentrations of ammonium sulfate and lactic acid. According to the results, the sulfuric acid solution favored the solubilization of both La3+ and Sm3+ elements. The solubilization of REE in the presence of ammonium sulfate showed no significant differences as a function of the leaching time but favored the solubilization of Y3+ and Tb3+. More efficient solubilization of Sm3+ was observed with the addition of lactic acid at a concentration of 30 g L-1, leading to 90% (4.5 ppm) of Sm3+ extraction. The solubilization of La3+ was favored by the contact time, with higher Sm3+ extraction yields in 14 days of leaching.