Evaluation of acids onto the light rare earth elements dissolution from weathered residual rare earth ore activated by mechanochemical treatment by grinding

The objective of this study is to evaluate the effect of acids on light rare earth elements dissolution from weathered residual rare earth ore after mechanochemical reaction by grinding. In the case of sulfuric acid leaching, the maximum of light rare earth elements dissolution was obtained when the initial sulfuric acid concentration was 5.0 mol/dm3 and leaching time was 24 hours. Thus, we performed sulfuric, hydrochloric and nitric acid leaching experiments at the same condition. The obtained results highlighted that the best light rare earth elements dissolution among these acids achieved by hydrochloric acid leaching. On the other hand, equivalent light rare earth elements dissolution except cerium was achieved by nitric acid leaching. From x-ray absorption fine structure analysis, it was revealed that cerium oxide(IV) (CeO2) was produced after nitric acid leaching because of redox reaction between cerium and nitrate ion.