Recovery and separation of rare earth elements from an acid mine drainage-like solution using a strong acid resin

Abstract

Considered critical and strategic, the rare earth elements (REE) can be found in ores as well as in secondary sources such as acid mine drainage (AMD). The present work studies the ion exchange process to recover and separate the REE present in a solution similar to an acid mine effluent containing La, Pr, Nd, Sm, Eu, Gd, Dy, Er, metal impurities (Al, Ca, Mg) and sulfate (SO42−). The loading experiments were carried out in columns filled with a strong acid cation resin. The feed solution contained 3.13 mmol L−1 of REE, 1.17 mmol L−1 of metal impurities and 11.6 mmol L−1 of sulfate, at pH 3.5. The elution/fractionation experiments were performed with NH4EDTA at 0.02, 0.05 and 0.30 mol L−1. The loading efficiencies were equal to 85 % (0.94 mmol g−1) for the REE and 30 % (0.15 mmol g−1) for the metal impurities. During loading, part of heavy REE and impurities were replaced by light REE. The best REE fractionation condition was obtained when 0.02mol L−1 NH4EDTA was employed. It was possible to separate the REE from Al and Ca. The final liquor contained 39.0 mmol L−1 of REE and 2.79 mmol L−1 of metal impurities. The process overall recovery was 83 %. The LEWATIT ® MDS 200H resin has shown to be suitable to recover and partially fractionate REE, including the separation of Sm, which has an ionic radius like Eu.