The Influence of Rare Earth Occurrence States in Weathered Crust Elution-Deposited Rare Earth Ores on Extraction Rate

Two samples from weathered crust elution rare earth ore in southern China were selected in this paper. Total REEs content in samples were analyzed by mixed acid digestion- inductively coupled plasma-mass spectrometry (ICP-MS), occurrence states of REEs were analyzed by ammonium sulfate leaching and sequential extraction, and the relationship between ammonium sulfate leaching rates and REE occurrence states were preliminarily discussed. The results showed that the ammonium sulfate leaching rates of REEs in the samples after grinding decreased by 21.5% and 51.6%, respectively. The ion-exchanged REEs in the samples decreased significantly, while the carbonate-bound state increased significantly. The iron-manganese oxide-bound state and humic acid-bound state slightly increased. The enrichment sequence of cerium (Ce) occurrence state is significantly different from other REEs, mainly existing in the iron manganese oxidation state and residue state. This also leads to differences between Ce and other REEs in the leaching rate of ammonium sulfate and the changes in occurrence state after grinding. The leaching rate of REEs other than Ce is positively correlated with the sum content of ion-exchange state and iron-manganese oxide-bound state, and negatively correlated with the sum content of carbonate-bound state and residual state.