Development of methods for the recovery оf rare-earth elements from the mineral resources of the Arctic

This paper summarizes the findings of the research aimed at the development of a new method for the integrated processing of naturally occurring and anthropogenic rare-earth raw materials based on the decomposition of rare-earth element (REE) concentrates in the presence of sulfocationite. Sorption and desorption of REE cations on a strongly acidic ion exchanger, sorbent regeneration, and REE recovery from eluates are discussed. A virtually zero-waste integrated process for apatite concentrate is proposed. The generalization of the research findings is aimed at demonstrating the prospects and universality of the proposed resource-saving and environmentally safe approach to the processing of various types of naturally occurring and anthropogenic rare-earth mineral feeds. The new methodology made it possible to develop a number of new hydrochemical processes united by a single approach, providing a qualitative increase in the processing performance of various types of rare-earth mineral feeds. The theoretical foundations of a unified approach to the processing of a wide range of minerals can significantly accelerate and cheapen the implementation of specific process circuits, significantly reduce reagent consumption and waste generation, simplify the separation of rare earth elements and impurities, and the separation of rare earth elements from naturally occurring radionuclides, fluorine, and phosphorus. The study was funded by the Kolarctic CBC 2014-2020 program, Project KO1030 SEESIMA — Supporting Environmental Economic and Social Impacts of Mining Activity.

THE NEWEST ANALYTICAL TECHNOLOGIES FOR DETERMINING RARE-EARTH ELEMENTS IN GRANITOIDS OF THE UKRAINIAN SHIELD

Introduction. To date, rare earth elements (REE) are used to manufacture most high-tech goods and are crucial in defense technologies (lasers, radars, and electromagnetic weapons), nuclear engineering, metallurgy, and others. All this determines the relevance of their study to assess the rare earth mineral resource base of Ukraine. Problem Statement. The determination of REE in rocks and minerals is a fundamental problem in geochemistry and petrology for understanding the processes of rock formation. However, it is a complex analytical task related to the similar chemical properties of these elements, which are caused by the "lanthanide compression effect". Purpose. The purpose is to develop analytical technologies for determining REE content by the ICP-MS method, to evaluate their content and distribution in granitoids of the Ukrainian Shield. Materials and Methods. The hybrid method of ICP-MS analysis and microwave decomposition of rocks and minerals has been used to measure the REE content. This technique has been tested and used to estimate the content and distribution of REE in fluorites and rare-metal granitoids of the Rusko-Polyanskyi massif of the Korsun-Novomirgorod pluton of the Ukrainian Shield. Results. Analytical technologies for determination of REE in granites and minerals have been developed. The method for determining REE in fluorites and granites without their prior concentration in the range from 0.01 to 1000 ppm with a relative standard deviation of 0.01–0.10 has been described. The content of rare earth elements in the Rusko-Polianskyi granites increases (218–797 g/t), the main concentrator of these elements is fluorite (692–26933 g/t REE). An inverse relationship has been observed between the REE content in fluorites and granites. Conclusions. The developed analytical technologies are the basis for establishing quality assessment criteria and developing principles for the rational use of rare-earth granitoids to create a rare-earth mineral resource base in Ukraine.

Rare earth mineral diversity controlled by REE pattern shapes

The line connecting rare earth elements (REE) in chondrite-normalised plots can be represented by a smooth polynomial function using λ shape coefficients as described by O'Neill (2016). In this study, computationally generated λ combinations are used to construct artificial chondrite-normalised REE patterns that encompass most REE patterns likely to occur in natural materials. The dominant REE per pattern is identified, which would lead to its inclusion in a hypothetical mineral suffix, had this mineral contained essential REE. Furthermore, negative Ce and Y anomalies, common in natural minerals, are considered in the modelled REE patterns to investigate the effect of their exclusion on the relative abundance of the remainder REE. The dominant REE in a mineral results from distinct pattern shapes requiring specific fractionation processes, thus providing information on its genesis. Minerals dominated by heavy lanthanides are rare or non-existent, even though the present analysis shows that REE patterns dominated by Gd, Dy, Er and Yb are geologically plausible. This discrepancy is caused by the inclusion of Y, which dominates heavy REE budgets, in mineral name suffixes. The focus on Y obscures heavy lanthanide mineral diversity and can lead to various fractionation processes to be overlooked. Samarium dominant minerals are known, even though deemed unlikely by the computational model, suggesting additional fractionation processes that are not well described by λ shape coefficients. Positive Eu anomalies only need to be moderate in minerals depleted in the light REE for Eu to be the dominant REE, thus identifying candidate rocks in which the first Eu dominant mineral might be found. Here, I present an online tool, called ALambdaR that allows interactive control of λ shape coefficients and visualisation of resulting REE patterns.