Rare Earth Elements Extraction from Coal Waste Using a Biooxidation Approach

Rare earth elements (REEs) are of great importance to modern society and their reliable supply is a major concern of many industries that utilize them in metal alloys, semiconductors, electrical equipment, and defense equipment. REEs in the coal waste have been revealed to be an alternative resource for REEs production. In this study, the extraction, recovery, and upgrading of the REEs from coal waste has been realized with the bioleaching and precipitation processes. Reliable and sustainable acid and oxidant production from the oxidation of the pyrite with Acidithiobacillus ferrooxidans to generate acid for leaching were realized in this research. The acidified bioleaching solution was used to extract REEs from coal waste, with 13–14% yields for most REE elements (~72 h of leaching). However, recovery for longer duration tests was significant higher (varies from 40–60% for individual REEs). After extraction, precipitation and separation processes were designed with the aid of Visual Minteq calculations and modeling to concentrate the REEs. With the procedures designed in this research, a final REEs precipitate product containing 36.7% REEs was produced.

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The Occurrence of Selected Radionuclides and Rare Earth Elements in Waste at the Mine Heap from the Polish Mining Group

Minerals ◽

10.3390/min11050504 ◽

2021 ◽

Vol 11 (5) ◽

pp. 504

Author(s):

Danuta Smołka-Danielowska ◽

Agata Walencik-Łata

Keyword(s):

Rare Earth ◽

Rare Earth Elements ◽

Mineralogical Composition ◽

Hard Coal ◽

Coal Waste ◽

Radiological Hazards ◽

Study Results ◽

Variable Distribution ◽

Spectrometry Technique ◽

Variable Content

The paper presents the results of research on rare earth elements (REY) and selected radionuclides in barren rocks deposited on a heap at a mine belonging to the Polish Mining Group (the largest producer of hard coal in EU countries). The maximum concentration of REEs determined in silstones was 261.6 mg/kg and in sandstones 221.2 mg/kg. The average uranium and thorium content in silstones was 6.8 mg/kg and 11.6 mg/kg, respectively. On the other hand, the samples of burnt coal shales contain on average 3.5 mg/kg of uranium and 9.7 mg/kg of thorium. In all coal waste samples, the REE values are higher than in hard coal (15.7 mg/kg). Carriers of REY, uranium, and thorium in coal waste are detritic minerals: monazite and xenotime, which are part of the grain skeleton of barren rocks. Coal waste samples are characterized by a variable distribution of REY concentrations as well as a variable content of radionuclides. The 226Ra, 228Ra, and 40K measurements in the investigated samples were performed using the gamma spectrometry technique. The concentrations of the analyzed isotopes differed depending on the mineralogical composition of the investigated samples. The present study results may be important in determining the possibility of utilization of wastes of barren rocks stored in the mine heap and in assessing environmental and radiological hazards.

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Changes in the Concentration of Some Rare Earth Elements in Coal Waste

Archives of Mining Sciences ◽

10.1515/amsc-2017-0037 ◽

2017 ◽

Vol 62 (3) ◽

pp. 495-507

Author(s):

Jacek Nowak ◽

Magdalena Kokowska-Pawłowska

Keyword(s):

Trace Elements ◽

Rare Earth ◽

Rare Earth Elements ◽

Clay Minerals ◽

Chemical Constituents ◽

Thermal Transformation ◽

Contact Metamorphism ◽

Coal Waste ◽

Coal Seams ◽

Phase And Chemical Composition

AbstractCoal waste is formed during coal mining and processing operations. That waste comprises mainly sedimentary rocks that occur in roofs and floors of underground workings and in partings in coal seams. It contains numerous trace elements, including rare earth elements (REEs). Hypergenic processes that take place in coal waste piles may lead to endogenous fires. Thermal transformations of waste have an effect on changes in its phase and chemical composition, including the concentration of trace elements.The paper presents changes in the content of selected rare earth elements (Sc, Y, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu) in wastes of varying degree of thermal transformation. The results of REE content determination in lump samples were subjected to statistical analysis and coefficients of correlation between the studied rare earth elements and the main chemical constituents were determined.The primary carriers of REEs in coal waste are clay minerals. Phase transformations that take place at high temperatures (including dehydroxylation of clay minerals and formation of minerals characteristic of contact metamorphism) cause changes in the concentration of rare earth elements.

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