Rare Earth Occurrence States of Weathered Crust Elution-Deposited Rare Earth Ores in Southern Yunnan

Abstract

To reveal the regularity of variation in the rare earth occurrence states of weathered crust elution-deposited rare earth ores, ore samples from different weathering crust layers were obtained by performing the sequential extraction procedure. The order of rare earth contents firmly obeyed the following sequence: the weathered layer > humic layer > partly weathered layer. The occurrence states of rare earth elements were mainly the ion exchange state, carbonate bound state, iron–manganese oxide state, organic binding state and residual state. The proportions of rare earth elements found in the rare earth ion exchange state of the weathered layer, humic layer and partly weathered layer were 78.55%, 73.53% and 53.88%, respectively. The light rare earth elements (LREEs) found in the rare earth ion exchange state were enriched in the upper part of the weathering crust, while the heavy rare earth elements (HREEs) were enriched in the lower part. There were also obvious negative anomalies in the content of cerium in the ion exchange state. The content of rare earth elements found in the carbonate bound state was small, and the rare earth partition pattern was basically consistent with that of the ion exchange state, which had little effect on the differentiation of the rare earth elements. The iron–manganese oxide state was mainly enriched with cerium, and the content of cerium increased with the depth of the weathering crust. The iron–manganese oxide state was the main factor causing the phenomenon of the anomaly in the cerium content. Meanwhile, the iron oxides in the iron–manganese oxide state were mainly hematite and goethite. The organic binding state mainly beneficiated yttrium and cerium by complexation and certain adsorption. The content of elements found in the rare earth residual state was related to the degree of weathering and reflected the release sequence of rare earth elements in the mineralization process. Clarifying the rare earth occurrence states is conducive to better revealing the metallogenic regularity of weathered crust elution-deposited rare earth ores. In addition, the results can provide a valuable reference for expanding the available rare earth resources and the efficient comprehensive utilization of rare earth ore.

Recovery of Rare Earth Elements from Ion-Adsorption Deposits Using Electrokinetic Technology: The Soil Conductivity Mechanism Study

“…Meanwhile, the current was recorded on an amperemeter (CY-high precision, Chiyi Hardware, Huaian, China). The water contents in P1-P4 were measured at various EKM time intervals (i.e., 1,3,6,12,24,36,48,60,72,84,96, and 120 h) as well. The concentrations of REE in P1-P4 were analyzed every 24 h by an inductively coupled plasma optical emission spectrometer (ICP-OES, OPTIMA 2000DV, PerkinElmer, Waltham, MA, USA).…”

“…where σ s and σ w are conductivities of solid-liquid and the liquid phase related to the concentration, respectively, in the dilute solution, the conductivity is proportional to the ion concentration and charge as shown in Equation (1). Similarly, we assumed that the soil conductivity is proportional to the total concentrations of various ions in the weathering crust soil, inducing Equations ( 1) and ( 5)-( 7), the soil conductivity can be expressed as Equation ( 8) when the parameters were simplified.…”

“…Rare earth elements (REEs), valued for their exceptional physical and chemical properties, find wide applications in modern industries including electronics, metallurgy, clean energy, and high-tech manufacturing [1,2]. Of particular significance are the heavy REEs (HREEs), which possess unparalleled value as they are irreplaceable on rockets, satellites, aircraft carriers, and fighters.…”

Effects of Ammonium Salts on Rare Earth Leaching Process of Weathered Crust Elution-Deposited Rare Earth Ores

“…As an extremely important non-renewable mineral resource, rare earth plays a vital role in global economic development [1][2][3]. In particular, the medium and heavy rare earth elements, represented by terbium and lutetium, show high economic value and are extremely scarce.…”