Selective precipitation of rare earth and critical elements from acid mine drainage - Part II: Mechanistic effect of ligands in staged precipitation process

Recovery of critical elements from secondary resources, such as acid mine drainage (AMD), has been deemed a potential path to support the raw materials needed to support the increasing high-tech and green energy developments. The precipitation patterns of critical elements in AMD treatment ponds differ when NaOH and Na2CO3 are used. In order to determine the reason for the difference in precipitation pattern of REEs and critical elements in these two conditions as well as the prospects of selective recovery of these elements, surface charge, particle size, and formation of the precipitates obtained from the treatment of AMD using a 3-stage precipitation process were studied. It was shown that the REEs surface complexation and co-precipitation with Al precipitates are unlikely. Particle size analysis concluded that the Al and Co-Mn precipitates tend to agglomerate after the initial precipitation of very fine particles. However, no agglomeration of the REE precipitates was observed.