Selective leaching of calcium from mechanically activated mixed rare earth concentrate

Abstract

The loss of rare earths (REs) takes place during the pre-decalcification process of mixed rare earth concentrate. In an effort to reduce such RE loss, a novel idea to improve the leaching selectivity of Ca to REs by applying selective mechanical activation was proposed. First, regarding the key minerals affecting the leaching selectivity of Ca to REs, the differences in the mechanical activation behaviors of CaF2 and REFCO3 were studied, and we find that the lattice strain of CaF2 increases from 0.21% to 0.42%, whereas that of REFCO3 increases from 0.31% to 0.40%. Notably, CaF2 demonstrates a larger lattice strain than REFCO3, indicating greater mechanical activation energy storage and higher leaching activity. Next, the HCl leaching process was studied. A significant leaching selectivity of Ca to REs, from 21.6 to 35.1, is achieved through mechanical activation. The Ca leaching rate reaches 80.7% when the RE loss is 2.3% in the activated sample. This study provides an novel approach for achieving selective extraction of specific components via mechanical activation pretreatment.