Recovery of Rare Earth Elements from Acid Mine Drainage

The recovery of rare earth elements (REEs) from acid mine drainage by cationic resins was investigated using batch experiments. The experiments were carried out with laboratory solution and with acid mine water enriched with REEs. The experimental conditions were: pH 1.3, 2.5 and 3.4, temperature 25±1⁰C, and the exchange resins were Dowex 50WX8 and Purolite C160. For the laboratory solution, it was observed that for all the REE, except cerium, the adsorption was > 85%. For the spiked acid water, the best results were obtained at pH 1.3 and the adsorption capacity of the resins for the REEs in mmol.g-1 are: Dowex 50WX8 (La=0.074, Y=0.067, Ce=0.079, Pr=0.077, Nd=0.077, Eu=0.070, Dy=0.070, Sm=0.074); Purolite C160 (La=0.074, Y=0.059, Ce=0.080, Pr=0.077, Nd=0.076, Eu=0.070, Dy=0.066, Sm=0.074). The highest adsorption was obtained for La, around 89% for both resins. The resins also adsorbed other elements from the spiked acid water, such as Mn, Ca, Mg, Zn and Al. The resins adsorbed less than 10 to 12% of these elements, considered as impurities. The total loading capacity of the resins is 0.668 mmol g-1 for Dowex 50WX8 and 0.643 mmol g-1 for Purolite C160. However, the results showed that the resins have similar adsorption capacity for the REE.