Recovery of rare earth elements from coal fly ash by integrated physical separation and acid leaching

Pan, Jinhe; Nie, Tiancheng; Hassas, Behzad Vaziri; Rezaee, Mohammad Ahangarzadeh; Wen, Zhiping; Zhou, Changchun

doi:10.1016/j.chemosphere.2020.126112

Cited by 104 publications

(40 citation statements)

References 47 publications

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“…Coal fly ash particles can be separated into different fractions based on their contrasts in physical characteristics such as density, particle size, magnetism, and surface hydrophobicity [19,24,[83][84][85][86][87]. Rather than processing the bulk ash material, REE extraction from certain fractions that are relatively more enriched in REEs will make the overall recovery more economically viable.…”

Section: Physical Beneficiation Of Rees From Coal Combustion Ashmentioning

confidence: 99%

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A Comprehensive Review of Rare Earth Elements Recovery from Coal-Related Materials

et al. 2020

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Many studies have been published in recent years focusing on the recovery of rare earth elements (REEs) from coal-related materials, including coal, coal refuse, coal mine drainage, and coal combustion byproducts particularly fly ash. The scientific basis and technology development have been supported by coal geologists and extractive metallurgists, and through these efforts, the concept has progressed from feasibility assessment to pilot-scale production over the last five years. Physical beneficiation, acid leaching, ion-exchange leaching, bio-leaching, thermal treatment, alkali treatment, solvent extraction, and other recovery technologies have been evaluated with varying degrees of success depending on the feedstock properties. In general, physical beneficiation can be a suitable low-cost option for preliminary upgrading; however, most studies showed exceedingly low recovery values unless ultrafine grinding was first performed. This finding is largely attributed to the combination of small RE-bearing mineral particle size and complex REE mineralogy in coal-based resources. Alternatively, direct chemical extraction by acid was able to produce moderate recovery values, and the inclusion of leaching additives, alkaline pretreatment, and/or thermal pretreatment considerably improved the process performance. The studies reviewed in this article revealed two major pilot plants where these processes have been successfully deployed along with suitable solution purification technologies to continuously produce high-grade mixed rare earth products (as high as +95%) from coal-based resources. This article presents a systematic review of the recovery methods, testing outcomes, and separation mechanisms that are involved in REE extraction from coal-related materials. The most recent findings regarding the modes of occurrence of REEs in coal-related materials are also included.

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Section: Physical Beneficiation Of Rees From Coal Combustion Ashmentioning

confidence: 99%

“…Two physical beneficiation processes are shown in Figure 5. In both circuits, magnetic separation is performed prior to size fractionation, whereas in another study by Pan et al [87], the sequence is reversed. Therefore, no fixed strategy has been proposed for the physical beneficiation process.…”

Section: Physical Beneficiation Of Rees From Coal Combustion Ashmentioning

confidence: 99%

A Comprehensive Review of Rare Earth Elements Recovery from Coal-Related Materials

et al. 2020

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“…The recycling of CFA using the unit hydrometallurgical operations can help to reduce the environmental burden of hazardous waste and will improve the economy. Pan et al [105] studied recovery of REE from CFA by integrated physical separation and acid leaching. Using combined physical separation processes, the REE of CFA was enriched from 782 µg/g to 1025 µg/g.…”

Section: Recovery Of Ree From Phosphogypsum (Pg) and Coal Flying Ash (Cfa)mentioning

confidence: 99%

Advances in Understanding of the Application of Unit Operations in Metallurgy of Rare Earth Elements

Stopić

Friedrich

2021

Metals

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Unit operations (UO) are mostly used in non-ferrous extractive metallurgy (NFEM) and usually separated into three categories: (1) hydrometallurgy (leaching under atmospheric and high pressure conditions, mixing of solution with gas and mechanical parts, neutralization of solution, precipitation and cementation of metals from solution aiming purification, and compound productions during crystallization), (2) pyrometallurgy (roasting, smelting, refining), and (3) electrometallurgy (aqueous electrolysis and molten salt electrolysis). The high demand for critical metals, such as rare earth elements (REE), indium, scandium, and gallium raises the need for an advance in understanding of the UO in NFEM. The aimed metal is first transferred from ores and concentrates to a solution using a selective dissolution (leaching or dry digestion) under an atmospheric pressure below 1 bar at 100 °C in an agitating glass reactor and under a high pressure (40–50 bar) at high temperatures (below 270 °C) in an autoclave and tubular reactor. The purification of the obtained solution was performed using neutralization agents such as sodium hydroxide and calcium carbonate or more selective precipitation agents such as sodium carbonate and oxalic acid. The separation of metals is possible using liquid (water solution)/liquid (organic phase) extraction (solvent extraction (SX) in mixer-settler) and solid-liquid filtration in chamber filter-press under pressure until 5 bar. Crystallization is the process by which a metallic compound is converted from a liquid into a crystalline state via a supersaturated solution. The final step is metal production using different methods (aqueous electrolysis for basic metals such as copper, zinc, silver, and molten salt electrolysis for REE and aluminum). Advanced processes, such as ultrasonic spray pyrolysis, microwave assisted leaching, and can be combined with reduction processes in order to produce metallic powders. Some preparation for the leaching process is performed via a roasting process in a rotary furnace, where the sulfidic ore was first oxidized in an oxidic form which is a suitable for the metal transfer to water solution. UO in extractive metallurgy of REE can be successfully used not only for the metal wining from primary materials, but also for its recovery from secondary materials.

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“…The study of [8]shows that the recovery of REE from fly ash can be challenging due to the presence of a dominant amorphous fraction, whose solution requires strong acidic conditions. Fly ash particles can be considered as spherical structures made of amorphous phase that bind REEs in their interior, due to this structure during the recovery, it is necessary to create conditions in the solution so that the acid ions can act on the particles containing rare earth elements on as much of their surface as possible.…”

Section: Potential Recovery Of Rre From Coal Fly Ashmentioning

confidence: 99%

Rare earth elements in deposited hard coal fly ash in Poland

Woźniak

Gurdziel

2021

E3S Web Conf.

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Rare Earth Elements (REEs), due to their unique properties, are nowadays a desirable raw material, especially in the development of modern technologies. This paper describes a 4-step research methodology for the task of identifying the potential for REE recovery in landfilled fly ash. A literature analysis was performed on their significance, occurrence in both primary and secondary deposits. Opportunities for REE recovery from coal fly ash in conventional power plants were identified and selected technologies were described. Poland, as a country whose energy sector is to a large extent based on coal, has a potential in this respect. Taking into account studies of the Polish Central Statistical Office (GUS) and forecasts of the Polish energy policy, the article determines the approximate value of REE in the waste stream from coal-fired power plants burning hard coal.

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Recovery of rare earth elements from coal fly ash by integrated physical separation and acid leaching

Cited by 104 publications

References 47 publications

A Comprehensive Review of Rare Earth Elements Recovery from Coal-Related Materials

A Comprehensive Review of Rare Earth Elements Recovery from Coal-Related Materials

Advances in Understanding of the Application of Unit Operations in Metallurgy of Rare Earth Elements

Rare earth elements in deposited hard coal fly ash in Poland

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