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

Ji, Bin; Li, Qi; Tang, Honghu; Zhang, Wencai

doi:10.1016/j.fuel.2022.123145

Cited by 12 publications

(4 citation statements)

References 32 publications

(56 reference statements)

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“…The relatively high REE contents in the Fire Clay SG fractions correlate well with the findings of numerous studies that identified the middling fractions of the Fire Clay seam to be rich in REEs [31]. The REEs in the middling of Fire Clay coal have been reported to be associated with the mineral matter and exist as finely dispersed monazite, xenotime, zircon and crandallite group minerals with a lower degree of crystallinity [10,11,31,32]. This would necessitate the use of roasting and possibly the assistance of chemical additives to extract the REEs associated with coal deposits [22].…”

Section: Mineralogy and Ree Analysissupporting

confidence: 83%

“…Calcination also had a significant impact on the REE leaching characteristics for the density fractions of the Fire Clay material (Figure 10). Calcination of the Fire Clay 2.20 SG sink sample, which comprises primarily of the ash material, increased the recovery values for total REEs by more than 20 absolute points at 600 • C. The positive association of REE recovery and temperature maximizes the recovery at 600 • C and flips to an inverse relationship post-600 • C. Based on the results, it can be concluded that the Fire Clay density fractions have higher amounts of insoluble REEs trapped in the solid matrix [32]. The recovery of REEs increases with temperature but the effect of calcination is more pronounced for the lower density fractions with specific gravities less than 1.80.…”

Section: High-temperature Calcination Testsmentioning

confidence: 81%

“…tionship post-600 °C. Based on the results, it can be concluded that the Fire Clay density fractions have higher amounts of insoluble REEs trapped in the solid matrix [32]. The recovery of REEs increases with temperature but the effect of calcination is more pronounced for the lower density fractions with specific gravities less than 1.80.…”

Section: High-temperature Calcination Testsmentioning

confidence: 91%

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Pretreatment of Bituminous Coal By-Products for the Hydrometallurgical Extraction of Rare Earth Elements

Gupta¹,

Nawab

Honaker

2023

Minerals

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Low-temperature plasma (LTP) oxidation has been widely used to study the mineralogy of the mineral matter existing in coal sources. The current study investigated the potential of LTP oxidation as a pre-treatment method to improve rare earth element (REE) leachability from coal and its by-products. Representative density-fractionated samples of Baker and Fire Clay coarse refuse seam materials were ground to a top size of 180 µm and subjected to low-temperature plasma oxidation. Subsequently, the treated samples were leached at 1% w/v solids concentration and 75 °C for 5 h using (i) de-ionized (DI) water, (ii) 0.1 mol/L of ammonium sulfate, and (iii) 1.2 mol/L of sulfuric acid. It was determined that LTP treatment improved REE leaching characteristics, especially the leaching of heavy REEs (HREE), existing in the lighter density fractions of the Baker seam coarse refuse material. For instance, the HREE recovery for the 1.6 specific gravity (SG) float fraction increased from 8% to 33% using 0.1 mol/L of ammonium sulfate solution after 32 h of LTP treatment. This finding indicated that HREEs associated with the organic matter were released by the LTP treatment and adsorbed onto the surfaces of highly negative charged mineral matter and was exchanged with ammonium to allow their recovery. Similarly, when using 1.2 mol/L of sulfuric acid, the HREE recovery increased from 23% to 53% for the 1.6 SG float fraction. Interestingly, LTP oxidation did not provide significant improvement in REE recovery from the 2.2 sink density fractions, which was likely due to its lower organic content. No significant benefits were observed when treating the Fire Clay coarse refuse material, which was likely due to the lack of organic affinity and the difficult-to-leach REE minerals associated with the coal source such as monazite, xenotime, and zircon. Conversely, high-temperature oxidation within a temperature range of 600–750 °C significantly improved REE leaching characteristics for both coal sources. Improvement in REE recovery was due to decarbonization of the material, clay dehydroxylation and subsequent conversion of liberated REE-bearing minerals into a more leachable form. However, increasing the temperature above 800 °C decreased REE recovery due to the conversion of meta-kaolinite into mullite, which is chemically stable.

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Section: Mineralogy and Ree Analysissupporting

confidence: 83%

Section: High-temperature Calcination Testsmentioning

confidence: 81%

Section: High-temperature Calcination Testsmentioning

confidence: 91%

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Pretreatment of Bituminous Coal By-Products for the Hydrometallurgical Extraction of Rare Earth Elements

Gupta¹,

Nawab

Honaker

2023

Minerals

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“…A large amount of REEs are dispersed in the amorphous structure of fly ash [13,27] , while alkali pretreatment under proper conditions can destroy the amorphous structure, thus increasing the recovery of REEs from fly ash. Although the recovery of REEs from coal waste is likely improved through alkali pretreatment, little research has been conducted in this area [28] .…”

Section: Introductionmentioning

confidence: 99%

Alkali pretreatment effects on acid leaching recovery of rare earth elements from coal waste of the Western Kentucky No. 13 and Fire Clay seams

Li¹,

Ji²,

Xiao³

et al. 2022

Miner Miner Mater

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The recovery of rare earth elements (REEs) from the Western Kentucky No. 13 and Fire Clay coal wastes was enhanced by alkali pretreatment with concentrated NaOH solutions. The enhancements in the recovery of light REEs (LREEs) are more significant than those of heavy REEs (HREEs). For example, after treating with 5 M NaOH at 90 °C, the recovery of LREEs from the Western Kentucky No. 13 coal waste increased from 26% to 71%, while the recovery of HREEs only increased from 29% to 41%. Based on mineralogical studies through scanning electron microscopy-energy dispersive X-ray spectroscopy and X-ray diffraction analyses, two mechanisms were proposed to explain the positive effect of alkali pretreatment: (1) decomposition of rare earth minerals (primarily crandallite-group minerals) during the alkali pretreatment, and (2) liberation of encapsulated REE-bearing particles due to the enhanced dissolution of clay minerals. The more significant enhancements in the recovery of LREEs were explained by the fact that the REEs comprised in the crandallite-group minerals were mainly LREEs. Compared with zircon, monazite, and xenotime, alkali pretreatment with 5 M NaOH led to a more significant decomposition of crandallite-group minerals. In order to further increase the recovery of REEs, particularly HREEs, harsher alkali treatment conditions are required.

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Efficient Leaching of Rare Earth Elements from Coal Gangue: A Mild Acid Process with Reduced Impurity Extraction

Wang,

Xu,

Cao

et al. 2024

J. Sustain. Metall.

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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

Cited by 12 publications

References 32 publications

Pretreatment of Bituminous Coal By-Products for the Hydrometallurgical Extraction of Rare Earth Elements

Pretreatment of Bituminous Coal By-Products for the Hydrometallurgical Extraction of Rare Earth Elements

Alkali pretreatment effects on acid leaching recovery of rare earth elements from coal waste of the Western Kentucky No. 13 and Fire Clay seams

Efficient Leaching of Rare Earth Elements from Coal Gangue: A Mild Acid Process with Reduced Impurity Extraction

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