Rare earth elements (REEs) recovery from coal waste of the Western Kentucky No. 13 and Fire Clay seams. Part II: Re-investigation on the effect of calcination

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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Leaching Kinetics of Rare Earth Elements from Fire Clay Seam Coal

Minerals ◽

10.3390/min10060491 ◽

2020 ◽

Vol 10 (6) ◽

pp. 491

Author(s):

Xinbo Yang ◽

Rick Q. Honaker

Keyword(s):

Activation Energy ◽

Rare Earth ◽

Sulfuric Acid ◽

Rare Earth Elements ◽

Froth Flotation ◽

Mineral Acid ◽

Product Layer ◽

Major Mechanism ◽

Mixed Control ◽

Fire Clay

Recovery of rare earth elements (REEs) from coal samples collected from the Fire Clay coal seam using diluted mineral acid solutions was investigated. The initial processing step was coal recovery using conventional froth flotation which concentrated the REEs in tailing material resulting in an upgrade to values around 700 ppm on a dry whole mass basis. Leaching experiments were performed on the flotation tailings material using a 1.2 M sulfuric acid solution adjusted to a temperature of 75 °C to study the extractability of REEs from coal material. The effect of particle size, leaching time, leaching temperature, and solid concentration on REE leaching recovery were evaluated. The kinetic data obtained from leaching over a range of temperatures suggested that the leaching process follows the shrinking core model with possibly a mixed control mechanism that may be a result of several heterogenous materials leaching simultaneously. Leaching recovery increased rapidly at the beginning of the reaction then slowed as the system reached equilibrium. The apparent activation energy determined from test data obtained over a range of temperatures using 1 M sulfuric acid was 36 kJ/mol for the first 20 min of reaction time and 27 kJ/mol for the leaching period between 20 and 120 min. The leaching of light REEs during the initial stage was determined to be driven by a chemical reaction, followed by the formation of a product layer, which required lower activation energy in the later stage of leaching. In regards to the heavy REEs, the major mechanism for leaching is desorption and the product layer formation does not affect the heavy REEs significantly.

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Association characteristic study and preliminary recovery investigation of rare earth elements from Fire Clay seam coal middlings

Fuel ◽

10.1016/j.fuel.2017.11.075 ◽

2018 ◽

Vol 215 ◽

pp. 551-560 ◽

Cited By ~ 25

Author(s):

Wencai Zhang ◽

Xinbo Yang ◽

Rick Q. Honaker

Keyword(s):

Rare Earth ◽

Rare Earth Elements ◽

Clay Seam ◽

Fire Clay

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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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