The Occurrence of Rare Earth and Radioactive Elements in the Associated Minerals with Raw Coal by EDX-SEM and XRD

Abstract

BACKGROUND The study on the occurrences of rare earth and radioactive elements in raw coal is of great significance in terms of whether the raw coal is concentrated or dispersed, the emission of fly ash is intercepted, and the rare earth elements (REEs) and radioactive elements are extracted from raw coal or fly ash. Previous studies showed that the occurrences of rare earth and radioactive elements in raw coal of various mining areas are different. OBJECTIVES To study the occurrences of rare earth and radioactive elements in 175 coal samples from two mining areas in the Huoxi coalfield of Shanxi Province. METHODS The analysis region was located by back scattered electron imaging (BSEI), and the main associated minerals were determined by EDS-mapping and powder X-ray diffraction. The trace associated minerals were determined by BSEI and EDS-point methods. RESULTS Six rare earth elements and a radioactive element were determined in the coal samples. Cerium, lanthanum and neodymium were associated with kaolinite minerals in the form of phosphate, partly occuring in minerals containing alumina or silicon oxide, and in carbon to a small degree. Yttrium and dysprosium existed independently in carbon in the form of phosphate or oxide, whereas scandium was found in zircon, and thorium is found in monazite. CONCLUSIONS The REE in the coal samples of the mining area were associated with other minerals in the form of fine-grained authigenic minerals, and a few occurred as independent minerals in carbon. The radioactive element thorium was associated with monazite.

Keywords

• feed coal
• associated minerals
• rare earth elements
• thorium
• energy dispersive x-ray spectrometry-scanning electron microscopy
• powder x-ray diffraction