Prerpints.org logo
Preprint
Review

Potential Future Alternative Resources for Rare Earth Elements: Opportunities and Challenges

Altmetrics

Downloads

612

Views

263

Comments

0

A peer-reviewed article of this preprint also exists.

supplementary.pdf (86.67KB )

This version is not peer-reviewed

Submitted:

27 January 2023

Posted:

28 January 2023

You are already at the latest version

Alerts
Abstract
Currently, there is increasing industrial demand for rare earth elements (REE) as these elements are now integral to the manufacture of many carbon-neutral technologies. The depleting REE ores and increasing mining costs are prompting to look for alternative sources for these valuable metals, particularly from waste streams. Although REE concentrations in most of the alternate resources are lower than current REE ores, some sources such as marine sediments, coal ash, and industrial wastes like red mud are looking promising with significant concentrations of REE in them. This review focuses on the alternative resources for REE such as ocean bottom sediments, continental shelf sediments, river sediments, stream sediments, lake sediments, phosphorites deposits, industrial waste products like red mud, and phosphogypsum, coal, coal fly ash, and related materials, waste rock sources from old and closed mines, acid mine drainage, and recycling of e-waste. Possible future Moon exploration and mining for REE and other valuable minerals are also discussed. It is evident that REE extractions from both primary and secondary ores alone are not adequate to meet the current demand, and sustainable REE recovery from the alternative resources described here is also necessary to meet the growing REE demand. An attempt is made to identify the potential of these alternative resources and sustainability challenges, benefits, and possible environmental hazards to meet the growing challenges in meeting the future REE requirements.
Keywords: 
Subject: Chemistry and Materials Science  -   Materials Science and Technology

1. Introduction

Seventeen elements in the periodic table including fifteen lanthanides (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) plus Sc, and Y are often collectively referred to as rare earth elements (REE). In nature, REE do not occur as single native metals, such as gold or silver, instead because of their similar physical and chemical properties very often they occur together in several geologic formations in many ores or minerals as minor or major constituents. Due to their unique physical, chemical, mechanical, electronic, magnetic, luminescent, phosphorescent, and catalytic properties, these elements have become exceptionally important during the last couple of decades, and there has been an explosion in the industrial application of these elements in different high technology devices such as smartphones, computers, televisions, light emitting diodes, catalysts for fuel cells, corrosion inhibitors, hard drives, and magnets for wind turbines and other power generating systems. They are also crucial for national security as they are extensively used in several military defence systems [1,2,3]. Their important medical applications include metallic implants, lasers, and magnetic resonance imaging (MRI) measurements [4]. REE are vital even to the space industry as they are used in everything from launch vehicles to national defence and commercial communications and observation satellites. REE are also used in making catalysts in several industrial processes as well as in the fabrication of autocatalytic catalytic converters in transport vehicles [5,6]. Although REE deposits are found practically in all parts of the world, currently there is a global shortage, due to the decreasing number of economically profitable deposits. Also, our reliance on REE in our high-tech gadget-hungry world is growing with time, but their supply is far from secure. Unfortunately, the conventional ore resources are becoming depleted, as the demand for REE increases, and the industry is paying attention to unconventional resources like coal, recycling, and marine sediments as alternative sources for these elements. It is also very important to maintain a proper supply chain to meet the demand for the development of highly advanced technologies. Even the substitution of REE by other cheaper metals is difficult for most applications, though powerful permanent magnets made out of iron and nitrogen (iron nitride, Fe16N2) are helping the automotive and wind energy industries in a small way [7]. Pavel et al. [8] studied the possibilities of substitution of REE in wind turbines in order to reduce the dependency on REE, but later it was found that these claims were impossible without neodymium. As a result, recycling is being scaled up in several countries at present. Many approaches such as physical, chemical, and biological procedures such as pyrometallurgy, solvent extraction, and membrane separation are available for the efficient extraction of REE from these resources [9]. One very important aspect is that currently extracted ore grades, with an average of 5% REE and running as high as 15%, have far higher concentrations than most of the discussed alternative sources [10]. Since only a few countries are producing these elements on a commercial scale, meeting the growing demand for these elements is becoming exceedingly difficult in several other countries. As the demand for REE is growing and the conventional ores are also getting depleted, attention is turning to unconventional and alternative REE resources. Therefore, it is very important to understand the global REE resources including alternative resources, and their production scenario and take measures against future prospects. Therefore, this study which is the first of its kind brings out a summary of the primary, and secondary, REE deposits, and a comprehensive report on alternative REE resources and their potential to meet the current and future demand. This article also serves as technical information for alternative resources for REE other than the primary and secondary resources to policymakers and other stakeholders who are concerned. Before knowing more about alternative REE resources, a short review of the major REE primary and secondary deposits is presented below:

2. REE deposits

Although REE comprise significant amounts of a wide range of minerals including oxides, silicates, carbonates, phosphates, and halides, almost all production comes from less than ten minerals such as apatite, monazite, xenotime, allanite, and bastnasite [11]. Currently, these deposits are mainly located in China, Brazil, Vietnam, Russia, and India. Though China has been dominating in this area, several other countries such as the USA, Australia, Turkey and Sweden have successfully discovered new REE deposits recently. REE deposits are divided into primary (formed by magmatic, hydrothermal and/or metamorphic processes) and secondary deposits (formed by weathering and sedimentary transport) depending on their form of occurrence, genetic associations, and mineralogy [12]. Figure 1 Illustrative view of different types of REE resources including the potential alternate future resources [13]

2.1. Primary deposits

Primary deposits of REE are commonly associated with carbonatites and alkaline igneous rocks, pegmatites, iron oxide copper-gold deposits, and vein and skarn deposits. Of these carbonatites and peralkaline silicate rocks with appreciable concentrations of REE are the most important REE resources [13,14]. These REE deposits in igneous rocks have played an important role in meeting the industrial demand for decades. These igneous mineral deposits can be divided into five distinct categories depending on the provenance, the evolution of the magma, and the rock types hosting mineralization: i) carbonatites, ii) peralkaline silica undersaturated rocks, iii) peralkaline granites and pegmatites, iv) pegmatites associated with sub- to metaluminous granites, and v) Fe oxide–phosphate deposits [15]. More insights on these primary REE deposits were presented by Weng et al. [16] and Dushyantha et al. [12]. Skarn deposits of REE are important in sustainable economic development across the world [17]. In Fe oxide–phosphate deposits, these elements are concentrated in apatite minerals [18].

2.2. Secondary deposits

Some of the important secondary deposits of REE are laterites, ion adsorption clays, and placer deposits. Ion-adsorption deposits, which are formed due to the erosion and weathering of primary deposits from within weathering crusts which supply more than 95% of the global HREE demand. Intensive lateritic weathering of bedrocks under tropical or sub-tropical climatic conditions can form a variety of secondary deposits which may range in composition from aluminous bauxites to iron and niobium, and REE [19]. Recently Jo and Shin [20] reported REE-enriched weathered anorthosite rocks with ΣREE range 242 – 857 µg/g. Ionic clays, formed by the natural weathering process of REE-minerals and the adsorption of the resulting liberated REE ions onto the clay surface, are an important resource for critical REE. These ion-adsorption clay deposits are most suitable for in situ leaching mining, and supply > 95% of the global HREE demand [21]. Ion-adsorption REE deposits are mostly developed due to weathering of REE-rich granites and REE ions are mainly adsorbed on clay minerals [22]. Currently, regolith-hosted REE deposits from areas with abundant REE deposits have become one of the major sources of global REE. Regolith-hosted deposits with abundant REE around Meizhou City, Guangdong Province, South China with the highest ΣREE of 1162 μg/g were reported recently by Lin et al. [23]. The REE concentrations in the regolith-hosted REE deposits in Chilean coastal range of the central Andes were found to be up to 2000 µg/g [24]. Beach sands are the products of a combination of weathering, fragmentation and degradation and are well-known for their economic concentration of heavy minerals like monazite, illuminate, zircon, rutile, allanite, sillimanite and garnet. REE are abundant in some of these minerals, particularly in monazite and allanite [25]. Black shales can also be considered as secondary resource for these valuable metals. Recently, El-Anwar et al. [26] reported REE enrichment (average 255.3–325.3 µg/g) in black shales of the Safaga-Qussier sector, Egypt. Another such study is reported from the rock-soil-moss system in the black shale area in China with an average concentration of ∑REE around 245 µg/g [27]. These recent studies together with the industry standard of ~ 300 µg/g cut-off grade for mining, prompt more studies on black shale formations worldwide before considering the black shale deposits as a source of REE. Ketris and Yudovich [28] reported an average worldwide REE concentration of 134.19 in black shales. Geothermal fluids are potentially significant sources of valuable minerals and metals. The total REE in geothermal waters in places like Iceland can go up to 21.76 µg/g [29]. Kurzawa et al. [30] in an attempt to understand the REE concentrations in the mineral and thermal waters in the Polish Lowlands, found that high temperature (T > 60 °C) favoured the release of the more easily soluble REE from rocks into the water. Wei et al. [31] recently reported the total REE content of the geothermal water in the range of 0.059‒0.547 ng/ml, in the Ganzi–Litang fault, western Sichuan, China. The REE contents in geothermal waters are related to the reservoir lithology and are significantly influenced by pH and HCO3−, Na+, and Mn minerals. Though the REE content in geothermal waters is not considerable, if the abundant geothermal waters in places such as Iceland are taken into consideration, this source could be one of the most promising ones for REE with an efficient extraction technology. Li et al. [32] reported moderately high concentrations of REE ranging from105 to 195 µg/g at an average concentration of 151µg/g in oil shale samples in Tongchuan City, Southern Ordos Basin, China prompting the necessity for further investigations to understand the REE potential of these rocks.

2.3. Different types potential alternative deposits

So far, the identified primary and secondary REE resources are not able to meet the global demand and requirements. Finding out and establishing alternative resources for REE has been a topic of high interest for the past decade. Hence, lot of studies are going on for the identification of the potential alternative deposits to meet the growing demand world over. Powerful analytical techniques such as inductively coupled plasma mass spectroscopy (ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-AES), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDX), x-ray fluorescence spectrometry (XRF), x-ray diffractometry (XRD), laser induced breakdown spectroscopy (LIBS), and TESCAN, integrated mineral analysis (TIMA), are being utilised to understand the future potential of various alternative REE resources [33,34,35,36]. Following are some of the most important alternative sources for REE.

2.3.1. Ocean bottom sediments, and continental shelf sediments

Rifting of the continents has formed widespread sedimentary basins as rifting processes produce greater subsidence and lower basal heat flow, enlarging the depth extent of hydrothermal circulation and favouring the formation of giant deposits of elements such as copper, lead, zinc and nickel [37]. Several studies in recent times revealed that marine sediments such as ferromanganese crusts (cobalt crusts), manganese nodules, and marine mud from different parts of deep oceans are found to contain significant concentrations of REE and Y [38,39,40,41]. REE concentration ranges (µg/g) in some marine sediments from different oceans across the globe are presented in Table 1. Recent studies suggested that the continental shelf sediments of the Atlantic Ocean and Northern South China could potentially become resources for REE, similar to metalliferous deep-sea sediments [42,43]. Sediment samples from the northern South China Sea continental shelf reported concentrations of REE ranging from 32.97 µg/g to 349.07 µg/g, with an average concentration of 192.94 µg/g. These elevated concentrations of REE in the bottom sediments of Siberian seas in the Arctic were found to be mainly controlled by the characteristics of the original rocks [44]. Thus, deep-sea sediments because of their vast amounts of REE and a remarkably high proportion of HREE have attracted interest as a future REE resource. However, at the moment the regulatory authorities are not able to take decisions on future seabed mining because of the possible environmental effects of seabed mining [45].

2.3.2. Phosphorites and related deposits

Phosphate ores are divided into two main types on the basis of their origin: sedimentary and igneous phosphate rocks, about 80 % of which are derived from marine origin, and around 17 % are derived from igneous rocks, and the remaining deposits come from the residual sedimentary and guano-type deposits [63]. These rocks contain up to 1% ∑REE, and phosphate rock ores both igneous and sedimentary are, therefore, potential future resources of REE. Igneous phosphate rocks (e.g., Kola Peninsula, Russia, and Brazil), and sedimentary phosphate rocks which are formed by the deposition of phosphate-rich materials in marine environments and are also known as phosphorites are found in Florida, US, Morocco, and the Middle East [64]. Marine phosphorites concentrate REE including Y during the early diagenetic process. The REE content in seamount phosphorites is far greater than in continental margin phosphorites [39]. Morocco has the largest phosphate ore reserves in the world with 50 billion tons, followed by China and Egypt with 3.2 and 2.8 billion tons of phosphate ores respectively [65]. Based on the REE concentration data presented in Table 2. phosphorite deposits can be considered promising and could represent a profitable alternative source for REE in the future. Buccione et al. [66] made an attempt for understanding the economic potential of Northern African phosphorite deposits as alternative REE resources. The very high concentrations of REE (up to 1759 µg/g) in the Northern African phosphorites revealed that they can be considered promising alternative REE resources.

1.3.2. Stream sediments, river sediments and lake sediments

If REE-bearing source rocks are present in the catchment area of a river or a lake or a stream, the corresponding sediments continuously accumulate transported material and get enriched with respect to REE due to the physical and chemical weathering and erosion of source rocks. An increasing trend in the concentration of REE is seen in the sediments starting from river sediments to the estuary and adjacent bay in the case of Yellow River (Table 3). In sediments, Fe minerals and clay minerals usually promote the accumulation of REE. Recently, Klein et al. [74] undertook a study of the occurrence and spatial distribution of REE along with a few other elements such as Ga, Ge, Nb, In, Te, and Ta in the Rhine River sediments and its tributaries in Europe. The Rhine River represents one of the most important waterways in Europe accommodating a large number of industries with a catchment area of around 60 million inhabitants. The ∑REE concentrations show a steady increase along the Rhine River (Table 3) inferring that. the sources for these elements could be from natural as well as anthropogenic activities as the river sediments pose an important sink for anthropogenically introduced REE. Ramesh et al. [75] presented the distribution pattern of REE and several other trace elements in the sediments of the Himalayan rivers (Table 3). Since this data is more than two decades, the current concentrations can be considerably higher due to increased anthropogenic inputs as well as natural inputs. The Lake sediments in Sri Lanka recorded 1101 µg/g of REE (Table 3) because it is in the proximity of the Eppawala phosphate deposit [76]. Either REE containing source rocks or anthropogenic inputs, or both can be contribute for REE in all these sediments.

2.3.4. Coal, coal fly ash and related materials

Coal contains trace amounts of REE either in the form of discrete minerals or chemically bound to organic matter. Several investigations have demonstrated that coal ash may represent a promising alternative resource of REE as the demand for these metals is increasing. Some investigations revealed that the total REE concentrations in the organic and inorganic phases are 31 µg/g and 1,141 µg/g, respectively [82]. Coal fly ash is one of the largest industrial waste streams in the world which contains significant concentrations of REE and has the potential to become an important alternative resource for REE. Until now, this is being used as a building material for construction, concrete and road base, ceramics, etc. A of studies are going on the development of economically feasible procedures for the extraction of REE from coal and coal fly ash as there are large global reserves of coal and coal fly ash the world over. Yesenchak et al. [83] made a study of West Virginia's coal deposits for understanding their economic potential on an ash basis with respect to REE and also to gain insight into elemental modes of occurrence and possible enrichment mechanisms of these elements. Dai et al. [84] have provided an excellent review of anomalous REE and yttrium concentrations in coal. Table 4 presents the potential of these alternative REE resources. A big country like China uses about 4 billion tons of coal for its power plants to generate electricity which produces about 500–550 million tons of fly ash [85]. Coal and coal combustion products such as fly ash, bottom ash, and incinerator ash are found to contain significant amounts of REE as most coal samples contain minor amounts of rhabdophane, Nd, Ce, La (PO4).H2O, monazite, (Ce, La, Th, Nd)PO4, and xenotime (Y, Er)PO4 [86]. Some of the coal resources are enriched in REE due to the contributions from both detrital and hydrothermal sources (Hower et al. [87]. Significant concentrations of REE found in the global reserves of coal (average REE concentrations are estimated at 380–470 µg/g) and its by-products have prompted numerous research studies to understand their economic feasibility as alternative resources for REE and led to the development of several efficient procedures to extract REE from coal ashes [88]. Hence, coal fly ash is considered a potential alternative source for REE in recent years. Recently Lu et al. [89] reported that the REE and Y contents of coals from southwestern China are high, and the coal reserves and their by-products are suitable as potential REE sources. For example, in Poland which is the second biggest coal consumer in the European Union, there can be huge reserves of fly ash which is rich in REE. The concentrations of REE in certain coal deposits such as Pond Creek coalbed, Pike County, Kentucky, US can go up to 1000 µg/g or more. The collection and chemical analysis of over 4,000 samples including acid mine drainage, coal, and coal ash samples, with REE concentrations ranging from ng/ml for raw acid mine drainage materials to thousands of ppm (µg/g) for alternative coal-based resources such as coal and coal fly ash, USGS [90] recently demonstrated the technical feasibility of producing high-purity critical minerals, including REE, from low-grade coal-based materials. For a thorough understanding of the origin of anomalous concentrations of REE in coal, in addition to the influence of diagenetic processes such as temperature, pressure, and time associated with coal-rank advance, it is also necessary to understand a few more interaction mechanisms such as the influence of marine environments, input of hydrothermal fluids, volcanic ashes, and natural waters on peat swamp [83]. In addition, the presence of considerable amounts of radioactive nuclides (226Ra, 232Th, 40K and 238U) in fly ash must be also considered while developing efficient procedures for the extraction of REE, and see that these hazardous radionuclides should not escape in to the environment causing radioactive pollution in the surrounding [91,92].

2.3.5. Industrial by waste products like red mud, and phosphogypsum

Industrial by-products like low-grade bauxite, red mud, phosphogypsum, gem mining waste, and slags are found to contain substantial amounts of REE and are hence these are also considered alternative resources for REE. In fact, mining waste in many cases contain high concentrations of toxic substances and is considered a threat to the environment. However, mining waste discharges produced at the bauxite, phosphate rock and other ore mines may also become valuable resources, especially for REE. For example, in the process of refining titanium dioxide from the mineral ilmenite, REE oxides are produced as co-products. Another example is, during the leaching of bauxite by NaOH by the Bayer process for alumina production, a solid waste known as red mud is generated which contains substantial amounts of REE (Table 5). More than a decade back, the global annual generation of bauxite residue was around 120 million tonnes and 2.7 billion tonnes of this material was stockpiled by then [101]. According to Swain et al. [102], the global production of bauxite and red mud during 2010-19 is 2999 and 1518 million tons respectively. China, Australia, Brazil, India, the US, and Russia produce bauxite waste (red mud) in large quantities. Since the Bayer processes inception, large amounts of red mud are getting stockpiled, and with the increasing awareness of the availability of huge concentrations of REE in this industrial waste material, this would soon become an important alternative resource for REE [103]. Both igneous and sedimentary phosphate rock deposits are used for manufacturing fertilizers. Recent studies revealed that low–grade saprolite ore which is primarily exploited for its gold and copper, also contains significant amounts of REE [104]. The vast amount of gem mining industry tailings of past and present mining activities in Sri Lanka was proven to contain up to 0.3% REE which can become a potential secondary source for many critical raw materials, including REE [105]. Initially, people used red mud to make bricks, and in cement production, but its potential to be an alternative resource for REE has been recently realised. During the production of wet phosphoric acid and phosphate fertilizer from phosphate ores, a solid phosphogypsum by-product is produced to which most of the REE (>80%) in the phosphate ore are transferred [65]. Phosphogypsum can show low levels of radioactivity because of the presence of small amounts of uranium and thorium, but also useful as a valuable REE resource (Table 6). In many instances, industrial metallurgical waste dumps are contaminated with heavy metals posing a huge threat to both humans and the ecosystem. Phosphogypsum (CaSO4·2H2O) which is rich in REE is a waste generated during the production of the phosphoric acid process and the composition of impurities depends on the source of the phosphate. Phosphogypsum and uranium tailings are being used to extract REE in Poland [106]. Such industrial metal wastes can become sources for the extraction of REE. Baron [107] found significant amounts of valuable REE (Table 6) from such waste material in Poland. For example, Arctic Loparite ore tailings in the Kola Peninsula, North-western Russia are being effectively used to extract REE using bioleaching methods [131].

2.3.6. Waste rock sources from old and closed mines

Over 100 billion tonnes of solid waste are produced annually through mining operations the world over. The use of mine waste and mine tailings is attractive as this will reduce mining costs because the material is already excavated from the mines which would make it easier to access the minerals.
Recently Abaka-Wood et al. [132] provided a review highlighting the application of the new knowledge for the enhanced REE minerals recovery from selected iron-oxide-silicate-rich tailings and other alternative resources of similar mineralogical composition.

2.3.7. Acid mine drainage

Acid mine drainage (AMD) of certain industrial effluents such as coal, REE, and uranium mines, is also considered a potential source of REE though the concentration of ∑REE will be in the ng/ml range in the raw acid mine drainage samples. Table 7 presents concentrations of REE in AMD from different mines across the globe. This is a potential alternative REE resource and the recovery of REE remains largely unexplored though a lot of efficient extraction procedures are being developed. Acid mine drainage is produced by the oxidation of metallic sulphides present in some ores and tailings because of the instability of sulphides, which leads to the generation of sulfuric acid that promotes the leaching of the metals that make up these materials. Depending on the deposit type, acid waters can contain REE in significant concentrations. For example, the acid effluent of a closed uranium mine in Brazil contains 130 µg/ml REE. This acid effluent is treated with lime to produce a precipitate containing 7 % of REE [133], though there are other methods like ion exchange, solvent extraction, and co-precipitation for their recovery. The treatment of acid mine drainage is often carried out by neutralization, oxidation, and metal hydroxide precipitation. The precipitates obtained after the treatment of the Northern Appalachian Coal Basin in the US, the REE concentrations of the precipitates varied from 29 to 1286 µg/g with an average of 517 µg/g [134,135]. Since REE are present in low concentrations in mining wastewaters and acid mine drainage, adsorbents such as cellulosic materials and ion exchange materials could be more useful as part of extraction/preconcentration and/or purification processes. Pyrgaki et al. [136] in a recent review described mining waste and mine water as promising sources of REE if their extraction is coupled with the simultaneous removal of toxic pollutants. These authors reported very high concentrations of ∑REE+Y of 77 to 1957.7 µg/g in coal combustion ashes, bauxite residue and phosphogypsum, and 1.6 to 24.8 µg/ml in mine discharges from different coal and ore mining areas around the globe

2.3.7. Recycling of e-waste such as magnets, etc.

As the primary and secondary REE ores are getting depleted, alternative sources such as the recycling of e-waste for a substantial recovery of REE gained prominence in recent times [140]. Our dependence on REE for the electronic gadgets required for our daily life and green technologies is increasing, but the required supply of these elements is far from secure. Because of the environmental problems and the escalating cost of mining, the focus is now shifting toward recycling. Recycling REE to some extent can meet this demand. Recycling electronic wastes such as magnets, nickel-metal hydride batteries, hard discs from laptops, desktop computers, mobile phones, loudspeakers, scrap alloy, spent catalysts, and waste light-emitting diodes (LEDs) currently end up in landfills. Instead, these electronic devices can be used to recover REE as a mixture of their oxides which later can be reduced to the production of new magnets. More than 50 million tons of e-waste is generated globally every year [141]. Many economically important metals like REE, Cu, Co, Li, Sn, Ta, Ga, Au, and Ag can be recovered from this kind of electronic waste without affecting the environment [142]. The REE recovery from waste helps sustainable development through the circular economy. Particularly five elements, namely Nd, Eu, Tb, Dy, and Y are extremely important and their demand is expected to grow by 30% in the coming decade. For example, recycling of scrap Nd-Fe-B magnets usually provide substantial amounts of Nd, Pr, Dy, and sometimes Tb. Unfortunately, the recycling activity is not going on in a big way at present mainly because the e-waste contains a very less quantity of these metals. For example, each smartphone contains just 50 mg Nd and 10 mg Pr (Table 8), and in touch screen devices, some of these metals are distributed throughout the material at the molecular scale, though items like wind turbines contain substantial amounts of REE. On the other hand, huge quantities of REE are required for manufacturing certain items such as navy ships, defence aircraft, and permanent magnets. One of the major obstacles in recycling the REE is, the complexity of usages of these elements in a variety of applications with amounts ranging from a few milligrams to a few kilograms [143]. Another critical factor that is affecting the recycling activity of the REE is the lack of cost-effective methods for their extraction from e-waste both collectively and individually. Hence, the efficient recovery of these metals becomes entirely difficult and not cost-effective and as a result, until recently only less than 1% e-waste has been recycled for REE [144]. But nevertheless, both the US and Japan have intensified their research studies on recycling as the dependence on REE is comparatively high in these countries. Rizos et al. [145] reviewed the recycling of REE permanent magnets from end-of-life (EoL) products and opined that if systematically implemented, this could be among the main avenues for meeting the EU’s future REE needs and for mitigating supply risks.

2.3.9. Extraterrestrial

The moon, Earth’s nearest neighbour in space has long been considered a desirable location for space mining operations. Earlier studies have demonstrated that the Moon contains vast amounts of natural resources, like uranium, titanium, silicon, water, nickel, precious metals, REE, and 3He at much higher concentrations than those found on Earth [151]. Robotic technologies will be extensively utilised for future mining on the moon to achieve precise localization, and conceptual mapping of the lunar surface [152]. Consequently, both government organisations from countries like the US and China, and private sectors are engaged in future space mining activities [153]. Recently eight nations signed a US-led Artemis Program for moon exploration and beyond. The path is now clear for those eight nations — Australia, Canada, Japan, Luxembourg, Italy, the UK, the UAE, and the U.S. — to participate in NASA's Artemis program of crewed lunar exploration which aims to establish a sustainable human presence on and around the moon by the end of the decade. In addition, several missions planned for the exploration of the Moon’s surface in search of REE and other valuable minerals by countries such as the USA, China, India, Japan, and Russia [154].

5. Conclusions and future

Apart from other critical metals like Cu, Co, Ga, and Li, REE are also needed in big quantities for the necessary transition from fossil fuels to green energy solutions for the whole world to deliver net zero by 2050. Hence, there is a great need to intensify the exploration, mining, and extraction efforts for REE not only for the low-carbon energy transition but also for national security and consumer electronics applications. It is also time for looking into alternative resources for REE as the primary and secondary REE resources are dwindling fast and it is becoming difficult for identifying new resources. In addition, there is great uncertainty about the future REE supply from countries like China. The work presented here indicates the range and variety of waste streams with significant REE concentrations and with broader sustainability. Among the alternative resources described here deep-sea sediments, coal fly ash, and industrial waste products such as red mud and phosphogypsum are considered very promising. Future research will focus on finding cheaper and greener ways of extracting REE from these alternative resources. While developing efficient technologies for the extraction of REE from these alternate REE resources, there is a great need to be careful about the possible emissions of toxic metals like Cr, and Hg, radioactive metals like U, Th, and toxic organic compounds into the environment. Some recent studies have established the technical feasibility of a simple, economic, and scalable process for the recovery of REE from most of these alternative REE resources. Also, intense research is going on worldwide for the development of efficient technologies for the recovery of REE from these alternative sources which is expected to show a solution to the present global REE crisis. Some of the recent studies in this direction also suggest that other issues such as environmental, economic, and social factors will strongly influence the development of these alternative REE resources. There are also many questions about the alternative sources to becoming real-world REE sources for which plausible answers can be obtained only in the future.

Acknowledgement

The author would like to acknowledge the support of the Dr. Prakash Kumar, Director, CSIR-National Geophysical Research Institute, Hyderabad, India.

References

  1. Zhu, S.; Yang, L.; Bai, J.; Chu, Y.; et al. Ultra-stable Pt La intermetallic compound towards highly efficient oxygen reduction reaction. Nano Research 2022. [Google Scholar] [CrossRef]
  2. Mendez, J.A.C.; Vong, Y.M.; Bueno, J.J.P. Cerium and Other Rare Earth Salts as Corrosion Inhibitors—A Review. Protection of Metals and Physical Chemistry of Surfaces 2022, 1–10. [Google Scholar] [CrossRef]
  3. Balaram, V. Rare Earth Elements: Sources and Applications. In Environmental Technologies to Treat Rare Earth Elements Pollution: Principles and Engineering by Arindam Sinharoy; Piet Lens, N.L., Ed.; IWA Publishers: London, UK, 2021. [Google Scholar]
  4. Raju, C.S.K.; Cossmer, A.; Scharf, H.; Panne, U.; Lück, D. Speciation of gadolinium-based MRI contrast agents in environmental water samples using hydrophilic interaction chromatography hyphenated with inductively coupled plasma mass spectrometry. Journal of Analytical Atomic Spectrometry 2010, 25, 55e61. [Google Scholar] [CrossRef]
  5. Balaram, V. Environmental Impact of Pt, Pd and Rh Emissions from Autocatalytic Converters – A Brief Review of the Latest Developments, Handbook of Environmental Materials Management; Hussain, C.M., Ed.; Springer Nature Switzerland AG: 2020.
  6. Gong, Y.; Li, H.; Li, C.; Bao, X.; Hosono, H.; Wang, J. Insight into rare-earth-incorporated catalysts: The chance for a more efficient ammonia synthesis. Journal of Advanced Ceramics 2022, 11, 1–11. [Google Scholar] [CrossRef]
  7. Molla, S.; Farrok, O.; Islam, M.R.; Muttaqi, K.M. Application of iron nitride compound as alternative permanent magnet for designing linear generators to harvest oceanic wave energy. IET Electric Power Applications 2020, 14, 762–770. [Google Scholar] [CrossRef]
  8. Pavel, c.c. , Arántegui, R.L.; Marmier, A.; Schüler, D.; et al. Substitution strategies for reducing the use of rare earths in wind turbines. Resources Policy 2017, 52, 349–357. [Google Scholar] [CrossRef]
  9. Balaram, V Rare Earth Elements, Resources, Extraction Technologies, Limitations, and Global Trade – A Comprehensive Review. "Treatise on Geochemistry, 3rd Edition" Section 5, Sustaining Society, Ed. Gabriel Filippelli, Editors in Chief: Ariel Anbar and Dominique Weis, Elsevier (in press), 2024.
  10. Gaustad, G.; Williams, E.; Leader, A. Rare earth metals from secondary sources: Review of potential supply from waste and by-products. Resources, Conservation & Recycling 2021, 167, 105213. [Google Scholar] [CrossRef]
  11. Balaram, V.; Sawant, S.S. Indicator Minerals, Pathfinder Elements, and Portable Analytical Instruments in Mineral Exploration Studies. Minerals 2022, 12, 394. [Google Scholar] [CrossRef]
  12. Dushyantha, N.; Batapola, N.; Ilankoon, I.M.S.K.; Rohitha, S.; Premasiri, R.; Abeysinghe, B.; Ratnayake, N.; Dissanayake, K. The story of rare earth elements (REEs): Occurrences, global distribution, genesis, geology, mineralogy and global production. Ore Geology Reviews 2020, 122, 103521. [Google Scholar] [CrossRef]
  13. Balaram, V. Rare Earth Element Deposits - Sources, and Exploration Strategies. Journal of Geological Society of India 2022, 98, 1210–1216. [Google Scholar] [CrossRef]
  14. Dostal, J. Rare Earth Element Deposits of Alkaline Igneous Rocks. Resources 2017, 6, 34. [Google Scholar] [CrossRef]
  15. Chakhmouradian, A.R.; Zaitsev, A.N. Rare Earth Mineralization in Igneous Rocks: Sources and Processes. Elements 2012, 8, 347–353. [Google Scholar] [CrossRef]
  16. Weng, Z.; Jowitt, S.M.; Mudd, G.M.; Haque, N. A Detailed Assessment of Global Rare Earth Element Resources: Opportunities and Challenges. Economic Geology 2015, 110, 1925–1952. [Google Scholar] [CrossRef]
  17. Ibrahim, M.A.E. ; Kotel'nikov. Geological and Geochemical exploration methods for mineral resources (skarn deposits and rare earth elements) News of the Ural State Mining University, Earth sciences 2022, 2, 7–15. [Google Scholar]
  18. Aali, A.A.; Khakmardan, S.; Shirazi, A.; Nazerian, H. A Review of Mineralization of Rare Earth Elements in Iran. International Journal of Science and Engineering Applications 2022, 11, 92–99. [Google Scholar] [CrossRef]
  19. Cocker, M.D. Lateritic, supergene rare earth element (REE) deposits, in, Conway, F.M.; ed., Proceedings of the 48th Annual Forum on the Geology of Industrial Minerals, Phoenix, Arizona, Arizona Geological Survey Special Paper #9, 2014; Chapter 4, p. 1-18.
  20. Jo, J.; Shin, D. Geochemical characteristics of REE-enriched weathered anorthosite complex in Hadong district, South Korea. Geochemical Journal 2023. [Google Scholar] [CrossRef]
  21. Zhong, W.; Ouyang, J.; Yang, D.; Wang, X.; Guo, Z.; Hu, K. Effect of the in situ leaching solution of ion-absorbed rare earth on the mechanical behaviour of basement rock. Journal of Rock Mechanics and Geotechnical Engineering 2022, 14, 1210e1220. [Google Scholar] [CrossRef]
  22. Wang, H.; He, H.; Bao, W.Y.Z.; Liang, X.; Zhu, J.; Ma, L.M.; Huang, Y. Zircon texture and composition fingerprint HREE enrichment in muscovite granite bedrock of the Dabu ion-adsorption REE deposit, South China. Chemical Geology 2023, 616, 121231. [Google Scholar] [CrossRef]
  23. Lin, Z.; Wei, G.; Zhang, J.; Liang, X.; Huang, G. Origin and distribution of rare earth elements (REEs) in the soils of Meizhou City, southern China with high abundance of regolith-hosted REEs. Applied Geochemistry 2022, 147, 105514. [Google Scholar] [CrossRef]
  24. Bustos, N.; Marquardt, C.; Belmar, A.; Cordeiro, P. Regolith-hosted rare earth exploration in the Chilean Coastal Range of the Central Andes. Journal of Geochemical Exploration 2022, 234, 106934. [Google Scholar] [CrossRef]
  25. Sengupta, D.; Van Gosen, B. Placer-Type Rare Earth Element Deposits. Reviews in Economic Geology 2016, 18, 81–100. [Google Scholar] [CrossRef]
  26. El-Anwar, E.A.A. ., Abdelhafiz, M.A.; Salman, S.A. Rare earth and trace elements enrichment and implications in black shales of Safaga-Qussier sector, Egypt. Journal of African Earth Sciences 2022, 188, 104482. [Google Scholar] [CrossRef]
  27. Xu, Y.; Luo, C.; Gao, L.; Long, J.; Xu, H.; Yang, R. Anomalous concentrations and environmental implications of rare earth elements in the rock-soil-moss system in the black shale area. Chemosphere 2022, 307, 1, 135770. [Google Scholar] [CrossRef]
  28. Ketris, M.P.; Yudovich, Y.E. ; Estimations of Clarkes for Carbonaceous biolithes: world averages for trace element contents in black shales and coals. International Journal of Coal Geology 2009, 78, 135. [Google Scholar] [CrossRef]
  29. Zierenberg, R.; Fowler, A.; Reed, M.; Palanderi, J. Maximizing REE Recovery in Geothermal Systems. Final Technical Report - DOE project DE-EE0006748 2018, 1-30.
  30. Kurzawa, D.K.; Wysocka, I.; Porowski, A.; Drzewicz, P.; Vassileva, A. The occurrence and distribution of rare earth elements in mineral and thermal waters in the Polish Lowlands. Journal of Geochemical Exploration 2022, 237, 106984. [Google Scholar] [CrossRef]
  31. Wei, S.; Liu, F.; Zhang, W. Typical geothermal waters in the Ganzi–Litang fault, western Sichuan, China: hydro chemical processes and the geochemical characteristics of rare-earth elements. Environ Earth Sci 2022, 81, 538. [Google Scholar]
  32. Li, D.; Li, R.; Xue, T.; Wang, B.; et al. Characteristic and Geological Implications of Major Elements and Rare Earth Elements of Triassic Chang 7 Oil Shale in Tongchuan City, Southern Ordos Basin (China). Minerals 2018, 8, 157. [Google Scholar] [CrossRef]
  33. Balaram, V. Recent Trends in the Instrumental Analysis of Rare Earth Elements in Geological and Industrial Materials. Trends in Analytical Chemistry 1996, 15, 475–486. [Google Scholar] [CrossRef]
  34. Balaram, V. Current and emerging analytical techniques for geochemical and geochronological studies. Geological Journal 2021, 56, 2300–2359. [Google Scholar] [CrossRef]
  35. Palozzi, J.; Bailey, J.G.; Tran, Q.A.; Stanger, R. A characterization of rare earth elements in coal ash generated during the utilization of Australian coals. International Journal of Coal Preparation and Utilization. 2023. [CrossRef]
  36. Harikrishnan, S.; Ananthachar, A.; Choudhari, K.S.; George, S.D.; Chidangil, S.; Unnikrishnan, V.K. Laser-Induced Breakdown Spectroscopy (LIBS) for the Detection of Rare Earth Elements (REEs) in Meteorites. Minerals 2023, 13, 182. [Google Scholar] [CrossRef]
  37. Hoggard, M.J.; Czarnota, K.; Richards, F.D. Huston, D.L.; et al. Global distribution of sediment-hosted metals controlled by craton edge stability. Nature Geoscience 2020, 13, 504–510. [Google Scholar] [CrossRef]
  38. Balaram, V.; Banakar, V.K.; Subramanyam, K.S.V.; Roy, P.; Satyanarayanan, M.; Mohan, M.R.; Sawant, S.S. Yttrium and rare earth element contents in seamount cobalt crusts in the Indian Ocean. Curr. Sci. 2012, 110, 1334–1338. [Google Scholar]
  39. Balaram, V.; Satyanarayanan, M.; Murthy, P.K.; Mohapatra, C.; Prasad, K.L. Quantitative multi-element analysis of cobalt crust from Afanasy-Nikitin Seamount in the North Central Indian Ocean by inductively coupled plasma time-of-flight mass spectrometry. MAPAN-Journal of Metrology Society of India 2013, 28, 63–77. [Google Scholar]
  40. Hein, J.R.; Koschinsky, A.; Mikesell, M.; Mizell, K.; Glenn, C.R.; Wood, R. Marine Phosphorites as Potential Resources for Heavy Rare Earth Elements and Yttrium. Minerals 2016, 6, 88. [Google Scholar] [CrossRef]
  41. Singh, Y. Rare Earth Element Metallogeny in Indian Continental Shelf and Ocean Floor. J. Geol. Soc. India 2021, 97, 1396–1402. [Google Scholar] [CrossRef]
  42. Pourret, O.; Tuduri, J. Continental shelves as potential resource of rare earth elements. Scientific Reports 2017, 7, 5857. [Google Scholar] [CrossRef]
  43. Ge, Q.; Xue, Z.G.; Chu, F. Rare Earth Element Distributions in Continental Shelf Sediment, Northern South China Sea. Water 2020, 12, 3540. [Google Scholar] [CrossRef]
  44. Sattarova, V.; Astakhov, A.; Aksentov, K.; Shi, X.; et al. Geochemistry of the Laptev and East Siberian seas sediments with emphasis on rare-earth elements: Application for sediment sources and paleoceanography. Continental Shelf Research 2023, 254, 104907. [Google Scholar] [CrossRef]
  45. Balaram, V. Deep-sea mineral deposits as a source of critical metals for high-and green-technology applications. Minerals and Mineral Materials.
  46. Sa, R.; Sun, X.; He, G.; Xu, L.; Pan, Q.; Liao, J.; … Deng, X. Enrichment of rare earth elements in siliceous sediments under slow deposition: A case study of the central North Pacific. Ore Geology Reviews 2018, 94, 12–23. [Google Scholar] [CrossRef]
  47. Cui, Y.; Liu, J.; Ren, X.; Shi, X. Geochemistry of rare earth elements in cobalt-rich crusts from the Mid-Pacific M seamount. Journal of Rare Earths 2009, 27, 169e176. [Google Scholar] [CrossRef]
  48. Nath, B.N.; Balaram, V.; Sudhakar, M.; Pluger, W.L. Rare earth element geochemistry of ferromanganese deposits from the Indian Ocean. Marine Chemistry 1992, 38, 185e208. [Google Scholar]
  49. Gonzalez, F.J.; Somoza, L.; Maldonado, A.; Lunar, R.; Martinez-Frias, J.; Martin- Rubi, J.A.; Carrion, M.C. High technology elements in Co-rich ferromanganese crusts from the Scotia Sea. Revista de la Sociedad Española de Mineralogía 2010, 13, 113e114. [Google Scholar]
  50. Kato, Y.; Fujinaga, K.; Nakamura, K.; Takaya, Y.; Kitamura, K.; Ohta, J.; Toda, R.; Nakashima, T.; Iwamori, H. Deep-sea mud in the Pacific Ocean as a potential resource for rare-earth elements. Nature Geoscience 2011, 4, 535e539. [Google Scholar] [CrossRef]
  51. Yamazaki, T.; Nakatani, N.; Arai, R.; Sekimoto, T.; Katayama, H. Combined Mining and Pulp-Lifting of Ferromanganese Nodules and Rare-Earth Element-Rich Mud around Minamitorishima Island in the Western North Pacific: A Prefeasibility Study. Minerals 2021, 11, 310. [Google Scholar] [CrossRef]
  52. Yi, Z.; Zhong, C.; Javier, G.F.; Xufeng, Z.; et al. Rare earth elements and yttrium in ferromanganese deposits from the South China Sea: distribution, composition and resource considerations. Acta Oceanol. Sin. 2018, 37, 41–54. [Google Scholar] [CrossRef]
  53. Yasukawa, K.; Nakamura, K.; Fujinaga, K. , Machida, S.; et al. Rare-earth, major, and trace element geochemistry of deep-sea sediments in the Indian Ocean: Implications for the potential distribution of REY-rich mud in the Indian Ocean. Geochemical journal GJ 2015, 49, 621–635. [Google Scholar] [CrossRef]
  54. Prakash, L.S.; Ray, D.; Paropkari, A.L.; Mudholkar, A.V.; Satyanarayanan, M. , Balaram, V.; et al. Distribution of REEs and yttrium among major geochemical phases of marine Fe–Mn-oxides: Comparative study between hydrogenous and hydrothermal deposits. Chemical Geology, 2015; 312–313, 127–137. [Google Scholar] [CrossRef]
  55. Charlu, T.K.; Kalluraya, V.K.K. Ferromanganese encrustation from Lakshadweep area, Arabia Sea. Jour. Geol. Soc. India 1997, 49, 389–394. [Google Scholar]
  56. Dinesh, A.C.; Nisha, N.V.; Varghese, S.; Pillai, R.; Prasad, D.; Baraik, S.; Ramesh, R.P.; Joshi, R.K.; Meitei, S.I.; Jishnu, B.K.; Manoj, R.V.; Nagasundaram, M. Extensive occurrence of Fe-Mn crusts and nodules on seamounts in the southern Andaman Sea, India. Curr. Sci. 2020, 119, 704–708. [Google Scholar] [CrossRef]
  57. Kim, M.G.; Hyeong, K.; Yoo, C.M. Distribution of rare earth elements and yttrium in sediments from the Clarion-Clipperton Fracture Zone, northeastern Pacific Ocean. Geochemistry, Geophysics, Geosystems 2022, 3, e2022GC010454. [Google Scholar] [CrossRef]
  58. Qiu, Z.; Tao, C.; Ma, W.; Dias, Á.A.; Hu, S.; Shao, Y.; Yang, K.; Zhang, W. Material Source of Sediments fromWest Clarion–Clipperton Zone (Pacific): Evidence from Rare Earth Element Geochemistry and Clay Minerals Compositions. J. Mar. Sci. Eng. 2022, 10, 1052. [Google Scholar] [CrossRef]
  59. Takaya, Y.; Yasukawa, K.; Kawasaki, T.; Fujinaga, K.; Ohta, J.; Usui, Y.; Nakamura, K.; Kimura, J.; Chang, Q.; Hamada, M.; Dodbiba, G.; Nozaki, T.; Iijima, K.; Morisawa, T.; Kuwahara, T.; Ishida, Y.; Ichimura, T.; Kitazume, M.; Fujita, T.; Kato, Y. The tremendous potential of deep-sea mud as a source of rare earth elements. Scientific Report 2018, 8, 5763. [Google Scholar]
  60. Bu, W.R.; Shi, X.F.; Peng, J.T. Geochemical characteristics of seamount ferromanganese nodules from mid-Pacific Ocean. Chinese Science Bulletin 2003, 48, 98e105. [Google Scholar] [CrossRef]
  61. Piper, D.Z. Rare earth elements in ferromanganese nodules and other marine phases. Geochimica et Cosmochimica Acta 38 1974, 1007e1022. [Google Scholar] [CrossRef]
  62. Milinovic, J.; Rodrigues, F.J.L.; Barriga, F.J.A.S.; Murton, B.J. Ocean-Floor Sediments as a Resource of Rare Earth Elements: An Overview of Recently Studied Sites. Minerals 2021, 11, 142. [Google Scholar] [CrossRef]
  63. Broom-Fendley, S.; Siegfried, P.R.; Wall, F.; O’Neill, M.; Brooker, R.A.; Fallon, E.K.; Pickles, J.R.; Banks, D.A. The origin and composition of carbonatite-derived carbonate-bearing fluorapatite deposits. Miner. Deposita 2021, 56, 863–884. [Google Scholar] [CrossRef]
  64. Habashi, F. The recovery of the lanthanides from phosphate rock. Journal of Chemical Technology and Biotechnology. Chemical Technology 2007, 35, 5–14. [Google Scholar] [CrossRef]
  65. Roshdy, O.E.; Haggag, E.A.; Masoud, A.M. Leaching of rare earths from Abu Tartur (Egypt) phosphate rock with phosphoric acid. J Mater Cycles Waste Manag 2023, 25, 501–517. [Google Scholar] [CrossRef]
  66. Buccione, R.; Kechiched, R.; Mongelli, G.; Sinisi, R. REEs in the North Africa P-Bearing Deposits, Paleoenvironments, and Economic Perspectives: A Review. Minerals 2021, 11, 214. [Google Scholar] [CrossRef]
  67. Yu, L.M.; Liu, M.X.; Dan, Y.; Said, N.; Wu, J.H.; Hou, M.C.; Zou, H. The origin of Ediacaran phosphogenesis event: New insights from Doushantuo Formation in the Danzhai phosphorite deposit. South Ch HinaOre Geology Review 2023, 105230. [Google Scholar] [CrossRef]
  68. Shields, G.; Stille, P. Diagenetic constraints on the use of cerium anomalies as palaeoseawater redox proxies: an isotopic and REE study of Cambrian phosphorites. Chemical Geology 2001, 175, 29–48. [Google Scholar] [CrossRef]
  69. Emsbo, P.; McLaughlin, P.I.; Breit, G.N.; du Bray, E.A.; Koenig, A.E. Rare earth elements in sedimentary phosphate deposits: solution to the global REE crisis? Gondwana Research 2015, 27, 776–785. [Google Scholar] [CrossRef]
  70. Wu, C.; Yuan, Z.; Bai, G. Rare earth deposits in China. In: Jones, A.P.; Wall, Frances, Williams, C.T. (Eds.), Rare earth minerals–chemistry, origin and ore deposits. New York, Chapman and Hall, The Mineralogical Society Series 7, 1996; pp. 281–310.
  71. Ahmed, A.H.; Aseri, A.A.; Ali, K.A. Geological and geochemical evaluation of phosphorite deposits in northwestern Saudi Arabia as a possible source of trace and rare-earth elements. Ore Geology Reviews 2022, 144, 104854. [Google Scholar] [CrossRef]
  72. Haddad, F.; Yazdi, M.; Behzadi, M.; Yakymchuk, C.; Khoshnoodi, K. Mineralogy, geochemistry and depositional environment of phosphates in the Pabdeh Formation, Khormuj anticline, SW of Iran. 2022. [CrossRef]
  73. Wu, S.; Yang, H.; Fan, H.; Xia, Y.; Meng, Q.; He, S.; Gong, X. Assessment of the Effect of Organic Matter on Rare Earth Elements and Yttrium Using the Zhijin Early Cambrian Phosphorite as an Example. Minerals 2022, 12, 876. [Google Scholar] [CrossRef]
  74. Klein, O.; Zimmermann, T.; Hildebrandt, L.; Pröfrocka, D. Technology-critical elements in Rhine sediments - A case study on occurrence and spatial distribution. Science of the Total Environment 2022, 852, 158464. [Google Scholar] [CrossRef] [PubMed]
  75. Ramesh, R.; Ramanathan, A.; Ramesh, S.; Purvaja, R.; Subramanian, V. Distribution of rare earth elements and heavy metals in the surficial sediments of the Himalayan River system. Geochemical Journal 2000, 34, 295–319. [Google Scholar]
  76. Dushyantha, N.; Ratnayake, N.; Premasiri, R.; Batapola, N.; et al. Geochemical exploration for prospecting new rare earth elements (REEs) sources: REE potential in lake sediments around Eppawala Phosphate Deposit, in Sri Lanka. Journal of Asian Earth Sciences 2022, 105515. [Google Scholar] [CrossRef]
  77. Babu, S.S.; Ramana, R.V. V. Rao1, V.P.; Mohan, M.R.; Sawant, S.S.; Satyasree, N.; Krishna, A.K. Rare earth elements of sediments in rivers and estuaries of the east coast of India. Current Science 2021, 120, 519–537. [Google Scholar] [CrossRef]
  78. Gaillardet, J.; Dupre, B.; Allegre, C.J.; Negrel, P. Chemical and physical denudation in the Amazon river basin. Chem. Geol. 1997, 142, 141–173. [Google Scholar] [CrossRef]
  79. Ndjama, J.; Mafany, G.; Ndondo, R.G.N. ·, Belmond, B.E.; Bessa, A.Z.E. Rare earth elements in surface waters and sediments of the Mgoua watershed, south western Cameroon. Arabian Journal of Geosciences 2022, 5, 1001. [Google Scholar] [CrossRef]
  80. Han, Z.; Lu, H.; Zhang, B.; Cheng, Z.; Fu, W.; Lao, C.; Xu, C. Delineating preliminary prospective areas of ion-adsorption rare earth deposits with stream sediments geochemical mapping in South China. Journal of Asian Earth Sciences 2022, 105520. [Google Scholar] [CrossRef]
  81. Liu, Z.; Gu, X.; Lian, M.; Wang, J.; et al. Occurrence, geochemical characteristics, enrichment, and ecological risks of rare earth elements in sediments of “the Yellow river−Estuary−bay” system. Environmental Pollution 2023, 319, 121025. [Google Scholar] [CrossRef] [PubMed]
  82. Lin, R.; Bank, T.L.; Roth, E.A.; Granite, E.J.; Soong, Y. Organic and inorganic associations of rare earth elements in central Appalachian coal. International Journal of Coal Geology 2017, 179, 295–301. [Google Scholar] [CrossRef]
  83. Yesenchak, R.; Sharma, S.; Maxwell, A.E. Modes of Occurrence, Elemental Relationships, and Economic Viability of Rare Earth Elements in West Virginia Coals: A Statistical Approach. Minerals 2022, 12, 1060. [Google Scholar] [CrossRef]
  84. Dai, S. Graham, I.T.; Ward, C.R. A review of anomalous rare earth elements and yttrium in coal. International Journal of Coal Geology 2016, 159, 82–95. [Google Scholar] [CrossRef]
  85. Wu, L.; Ma, L.; Huang, G.; Li, J.; Xu, H. Distribution and Speciation of Rare Earth Elements in Coal Fly Ash from the Qianxi Power Plant, Guizhou Province, Southwest China. Minerals 2022, 12, 1089. [Google Scholar] [CrossRef]
  86. Ward, C.R. Analysis, origin and significance of mineral matter in coal: An updated review. International Journal of Coal Geology 2016, 165, 1–27. [Google Scholar] [CrossRef]
  87. Hower, J.C.; Eble, C.F.; Hopps, S.D.; Morgan, T.D. Aspects of rare earth element geochemistry of the Pond Creek coalbed, Pike County, Kentucky. International Journal of Coal Geology 2022, 104082. [Google Scholar] [CrossRef]
  88. Seredin, V.V.; Dai, S. Coal deposits as potential alternative sources for lanthanides and yttrium. International Journal of Coal Geology 2012, 94, 67–93. [Google Scholar] [CrossRef]
  89. Lu, Q.; Qin, S.; Bai, H. Geochemistry of rare earth elements and yttrium in Late Permian coals from the Zhongliangshan coalfield, southwestern China. Front. Earth Sci. 2022. [Google Scholar] [CrossRef]
  90. USGS. Recovery of Rare Earth Elements and Critical Materials from Coal and Coal By-products. United States Department of Energy, Washington DC; 2022; pp. 1-86.
  91. Madhusmita, M.; Sahu, S.K.; Poonam, M.; Gufran, B. Assessment of hazardous radionuclide emission due to fly ash from fossil fuel combustion in industrial activities in India and its impact on public. Journal of Environmental Management 2023, 328, 116908. [Google Scholar] [CrossRef]
  92. Menon, R.; Raja, P.; Malpe, D.; Subramanyam, K.S.V.; Balaram, V. Radio elemental characterization of fly ash from Chandrapur Super Thermal Power Station, Maharashtra, India. Current Science 2011, 100, 1880–1883. [Google Scholar]
  93. Sreenivas, T.; Serajuddin, M.; Moudgil, R.; Anand Rao, K. Developments in characterization and mineral processing of coal Fly ash for recovery of rare earth elements. In: Jyothi, R.K., Parhi, P.K. (Eds.), Clean Coal Technologies: Beneficiation, Utilization, Transport Phenomena and Prospective. Springer International Publishing, Cham. 2021; pp. 431–471. [Google Scholar] [CrossRef]
  94. Franus, W.; Motykam, M.M.W.; Wdowin, M. Coal fly ash as a resource for rare earth elements. Environ Sci Pollut Res. 2015, 22, 9464–9474. [Google Scholar] [CrossRef] [PubMed]
  95. Pan, J.; Long, X.; Zhang, L.; Shoppert, A.; Valeev, D.; Zhou, C.; Liu, X. The Discrepancy between Coal Ash from Muffle, Circulating Fluidized Bed (CFB), and Pulverized Coal (PC) Furnaces, with a Focus on the Recovery of Iron and Rare Earth Elements. Materials 2022, 15, 8494. [Google Scholar] [CrossRef] [PubMed]
  96. Rao, K.A.; Serajuddin, M. , Devi, G.R.; Thakurta, S.G.; Sreenivas, T. On the characterization and leaching of rare earths from a coal fly ash of Indian origin. Separation Science and Technology 2020. [Google Scholar] [CrossRef]
  97. Trinh, H.B.; Kim, S.; Lee, J. Recovery of rare earth elements from coal fly ash using enrichment by sodium hydroxide leaching and dissolution by hydrochloric acid. Geosystem Engineering 2022, 25, 1–2. [Google Scholar] [CrossRef]
  98. Hower, J.C.; Ruppert, L.F.; Eble, C.F. Lanthanide, Yttrium, and Zirconium anomalies in the Fire Clay coal bed, Eastern Kentucky. Int. J. Coal Geol 1999, 39, 141–153. [Google Scholar] [CrossRef]
  99. Rao, K.A.; Karan, R.; Babu, J.M.; Devi, G.R.; Sreenivas, T. Development of process scheme for recovery of rare earths from leachate of coal fly ash. Cleaner Chemical Engineering 2022, 4, 100078. [Google Scholar] [CrossRef]
  100. Bauer, S.; Yang, J.; Stuckman, M.; Verba, C. Rare Earth Element (REE) and Critical Mineral Fractions of Central Appalachian Coal-Related Strata Determined by 7-Step Sequential Extraction. Minerals 2022, 12, 1350. [Google Scholar] [CrossRef]
  101. Klauber, C.; Gräfe, M.; Power, G. Bauxite residue issues: II: Options for residue utilization. Hydrometallurgy 2011, 108, 11–32. [Google Scholar] [CrossRef]
  102. Swain, B.; Lee, C.G.; Park, J.R. Assessment of bauxite residue as secondary resource for rare earth metal and valorization challenges: A perspective. Resources. Conservation & Recycling Advances 2022, 14, 200078. [Google Scholar] [CrossRef]
  103. Archambo, M.; Kawatra, S.K. Red Mud: Fundamentals and New Avenues for Utilization. Mineral Processing and Extractive Metallurgy Review. 2020. [CrossRef]
  104. Abaka-Wood, G.B.; Johnson, B.; Addai-Mensah, J.; Skinner, W. Recovery of Rare Earth Elements Minerals in Complex Low-Grade Saprolite Ore by Froth Flotation. Minerals 2022, 12, 1138. [Google Scholar] [CrossRef]
  105. Dushyantha, N.; Ilankoon, I.M.S.K.; Ratnayake, N.P.; Premasiri, H.M.R.; Dharmaratne, P.G.R.; Abeysinghe, A.M.K.B.; Rohitha, L.P.S.; Chandrajith, R.; Ratnayake, A.S.; Dissanayake, D.M.D.O.K.; et al. Recovery Potential of Rare Earth Elements (REEs) from the Gem Mining Waste of Sri Lanka: A Case Study for Mine Waste Management. Minerals 2022, 12, 1411. [Google Scholar] [CrossRef]
  106. Kiegiel, K.; Miśkiewicz, A.; Koniecko, I.H.; Gajda, D.; Kołtuniewicz, G.Z. Perspective of Obtaining Rare Earth Elements in Poland}, Chapter 2, Lanthanides, editor = {Nasser S. Awwad and Ahmed T. Mubarak}, IntechOpen. [CrossRef]
  107. Baron, R. Results of Pilot Research Work on the Content of Rare Earth Elements in Metallurgical Wastes from Nowa Huta. Journal of the Polish Mineral Engineering Society 2022, 123–127. [Google Scholar] [CrossRef]
  108. Balaram, V. Rare earth elements: A review of applications, occurrence, exploration, analysis, recycling, and environmental impact. Geoscience Frontiers 2019, 10, 1285–1303. [Google Scholar] [CrossRef]
  109. Ujaczki E, Feigl V, Molnar M, Cusack P, Curtin T, Courtney R, O’Donoghue L, Davris P, Hugi C, Evangelou M, Balomenos, E, and Lenz, M. Re-using bauxite residues: benefits beyond (critical raw) material recovery. Journal of Chemical Technology and Biotechnology 2018, 93, 2498–2510. [CrossRef] [PubMed]
  110. Wang, W. Y. Pranolo, and C.Y. Cheng. Recovery of scandium from synthetic red mud leach solutions by solvent extraction with D2EHPA. Separation and Purification Technology 2013, 108, 96–102. [Google Scholar] [CrossRef]
  111. Botelho, A.B.; Costa, R.H.; Espinosa, D.C.R.; Soares, T.J.A. Recovery of scandium by leaching process from Brazilian red mud. In Rare Metal Technology. G.; Azimi, H., Kim, S., Ala, T., Neelameggham Ouch, N.R., Baba, A.A., Eds.; Sprnger: Berlin/Heidelberg, Germany, 2019. [Google Scholar]
  112. Abhilash, A.; Sinha, S.; Sinha, M.K.; Pandey, B.D. Extraction of lanthanum and cerium from Indian red mud. International Journal of Mineral Processing 2014, 127, 70–73. [Google Scholar] [CrossRef]
  113. Singh, U.; Thawrani, S.A.; Ansari, M.S.; Puttewar, S.P.; Agnihotri, A. Studies on beneficiation and leaching characteristics of rare earth elements in Indian red mud. Russian Journal of Non-Ferrous Metals 2019, 60, 335–340. [Google Scholar] [CrossRef]
  114. Narayanan, R.P.; Kazantzis, N.K.; Emmert, M.H. Process for scandium recovery from Jamaican bauxite residue: A probabilistic economic assessment. Materials Today: Proceedings 2019, 9, 578–586. [Google Scholar] [CrossRef]
  115. Borra, C.R.; Pontikes, Y.; Binnemans, K.; Van Gerven, T. Leaching of rare earths from bauxite residue (red mud). Minerals Engineering 2015, 76, 20–27. [Google Scholar] [CrossRef]
  116. Vind, J.A. ; Malfliet, B.; Blanpain, P.E.; Tsakiridis, A.H.; Tkacyk, V. Vassiliadou, and D. Panias. Rare earth element phases in bauxite residue. Minerals 2018, 8, 77. [Google Scholar]
  117. Deady, E.A.E. ; Mouchos, K.; Goodenough, B.J. Williamson, and F. Wall. A review of the potential for rare-earth element resources from European red muds: Examples from Seydişehir, Turkey and Parnassus-Giona, Greece. Mineralogical Magazine 2016, 80, 43–61. [Google Scholar] [CrossRef]
  118. Petropulu, M.O.; Tyberopulu, T. , Parissakis, G. Direct determination of lanthanides, yttrium and scandium in bauxites and red mud from alumina production. Anal Chim Acta 1994, 296, 305–313. [Google Scholar] [CrossRef]
  119. Ujaczki, E. ; Y.-S.; Zimmerman, V. Feigl, and M. Lenz. Recovery of rare Earth elements from Hungarian red mud with combined acid leaching and liqud-liquid extraction. Proceedings of the Bauxite Residue Valorization and Best Practices Conference, Leuven, Belgium, 2015; pp. 1–7.
  120. Martoyan, G.A. ; G.G. Karamyan, and G.A. Vardan. New technology of extracting the amount of rare earth metals from the red mud. IOP conference series: Materials Science and Engineering, Altay, Russia, 2016; p. 112.
  121. Zhang, S.; Zhao, F.; Liu, D.; Zhao, L.; Zhang, X.; Lin, J.; Dong, H.; Zhao, S.; Liu, X.; Zan, M. Modes of Occurrence of Critical Metal Elements (Li, REEs and Other Critical Elements) in Low-Grade Bauxite from Southern Shanxi Province, China. Minerals 2022, 12, 990. [Google Scholar] [CrossRef]
  122. Gamaletsos, P.N.; Godelitsas, A.; Filippidis, A.; et al. The Rare Earth Elements Potential of Greek Bauxite Active Mines in the Light of a Sustainable REE Demand. J. Sustain. Metall. 2019, 5, 20–47. [Google Scholar] [CrossRef]
  123. Amidi, A.; Razif, S.A.M.; Jabit, N.A.; Ariffin, K.S. Characterization of rare earth elements (REE) from industrial REE waste resources. Materials Today: Proceedings 2022, 66, 3140–3143. [Google Scholar] [CrossRef]
  124. Reid, S.; Tam, J.; Yang, M.; Azimi, G. Technospheric Mining of Rare Earth Elements from Bauxite Residue (Red Mud): Process Optimization, Kinetic Investigation, and Microwave Pretreatment. Scientific Reports 2017, 7. [Google Scholar] [CrossRef]
  125. Echeverry-Vargas, L.; Ocampo-Carmona, L.M. Recovery of Rare Earth Elements from Mining Tailings: A Case Study for Generating Wealth from Waste. Minerals 2022, 12, 948. [Google Scholar] [CrossRef]
  126. Shoppert, A.; Loginova, I.; Napol’skikh, J.; Kyrchikov, A.; Chaikin, L.; Rogozhnikov, D.; Valeev, D. Selective Scandium (Sc) Extraction from Bauxite Residue (RedMud) Obtained by Alkali Fusion-Leaching Method. Materials 2022, 15, 433. [Google Scholar] [CrossRef]
  127. Rivera, R.M.; Ounoughene, G.; Borra, C.R.; Binnemans, K.; Van Gerven, T. Neutralisation of bauxite residue by carbon dioxide prior to acidic leaching for metal recovery. Minerals Engineering 2017, 112, 92–102. [Google Scholar] [CrossRef]
  128. Kenzhaliyev, B.K.; Surkova, T.Yu. , Yessimova, D.M. Concentration of rare-earth elements by sorption from sulphate solutions. Complex Use of Mineral Resources. [CrossRef]
  129. Rychkov, V.N.; Kirillov, E.V.; Kirillov, S.V.; Semenishchev, V.S.; Bunkov, G.M.; Botalov, M.S.; … Malyshev, A.S. Recovery of rare earth elements from phosphogypsum. Journal of Cleaner Production 2018, 196, 674–681. [Google Scholar] [CrossRef]
  130. Ramirez, J.D.; Diwa, R.R.; Palattao, B.L.; Haneklaus, N.H.; et al. Rare earths in Philippine phosphogypsum: Use them or lose them. The Extractive Industries and Society 2022, 10, 101082. [Google Scholar] [CrossRef]
  131. Kasatkina, E.A. ; Shumilov,O.I.; Kirtsideli, I.Y.; Makarov, D.V. Bioleaching Potential of Microfungi Isolated from Arctic Loparite Ore Tailings (Kola Peninsula, Northwestern Russia). Geomicrobiology Journal. [CrossRef]
  132. Abaka-Wood, G.B.; Ehrig, K.; Addai-Mensah, J.; Skinner, W. Recovery of Rare Earth Elements Minerals from Iron-Oxide-Silicate-Rich Tailings: Research Review. Eng. 2022, 3, 259–275. [Google Scholar] [CrossRef]
  133. Silva, G.C.; Bertoli, A.C.; Duarte, H.A.; Ladeira, A.C.Q. Recovery of rare earth elements from sulfate-rich acid mine water: Looking through the keyhole the exchange reaction for cationic resin. Journal of Environmental Chemical Engineering 2022, 10, 108715. [Google Scholar] [CrossRef]
  134. Vass, C.R.; Noble, A.; Ziemkiewicz, P.F. The Occurrence and Concentration of Rare Earth Elements in Acid Mine Drainage and Treatment By-products: Part 1—Initial Survey of the Northern Appalachian Coal Basin. Mining, Metallurgy & Exploration 2019, 36, 903–916. [Google Scholar] [CrossRef]
  135. Vass, C.R.; Noble, A.; Ziemkiewicz, P.F. The Occurrence and Concentration of Rare Earth Elements in Acid Mine Drainage and Treatment Byproducts. Part 2: Regional Survey of Northern and Central Appalachian Coal Basins. Mining Metall. Explor. 2019, 36, 917–929. [Google Scholar] [CrossRef]
  136. Pyrgaki, K.; Gemeni, V.; Karkalis, C.; Koukouzas, N.; Koutsovitis, P.; Petrounias, P. Geochemical Occurrence of Rare Earth Elements in Mining Waste and Mine Water: A Review. Minerals 2021, 11, 860. [Google Scholar] [CrossRef]
  137. Larochelle, T.; Noble, A.; Strickland, K.; Ahn, A.; Ziemkiewicz, P.; Constant, J.; Hoffman, D.; Glascock, C. Recovery of Rare Earth Element from Acid Mine Drainage Using Organo-Phosphorus Extractants and Ionic Liquids. Minerals 2022, 12, 1337. [Google Scholar] [CrossRef]
  138. Gomes, P.; Valente, T.; Marques, R.; Prudencio, M.I.; Pamplona, J. Rare earth elements - Source and evolution in an aquatic system dominated by mine-Influenced waters. Journal of Environmental Management 2022, 322, 116125. [Google Scholar] [CrossRef]
  139. Li, X.; Wu, P. Geochemical characteristics of dissolved rare earth elements in acid mine drainage from abandoned high-As coal mining area, southwestern China. Environ Sci Pollut Res 2017, 24, 20540–20555. [Google Scholar] [CrossRef] [PubMed]
  140. Jyothi, R.K.; Thenepalli, T.; Ahn, J.W.; Parhi, P.K.; Chung, K.W.; Lee, J.-Y. Review of rare earth elements recovery from secondary resources for clean energy technologies: Grand opportunities to create wealth from waste. Journal of Cleaner Production 2020, 122048. [Google Scholar] [CrossRef]
  141. Islam, A.; Ahmed, T.; Awual, M.R.; Rahman, A.; et al. Advances in sustainable approaches to recover metals from e-waste-A review. Journal of Cleaner Production 2020, 244, 118815. [Google Scholar] [CrossRef]
  142. Lukowiak, A.; Zur, L.; Tomala, R.; LamTran, T.N.; et al. Rare earth elements and urban mines: Critical strategies for sustainable development, Ceramics International 2020, 46, 26247-26250. [CrossRef]
  143. Jowitt, S.M.; Werner, T.T.; Weng, Z.; Mudd, G.M. Recycling of the rare earth elements. Current Opinion in Green and Sustainable Chemistry 2018, 13, 1–7. [Google Scholar] [CrossRef]
  144. Ganguli, R.; Cook, D.R. Rare earths: A review of the landscape. MRS Energy & Sustainability: A Review Journal. [CrossRef]
  145. Rizos, V.; Righetti, E.; Kassab, A. Developing a supply chain for recycled rare earth permanent magnets in the EU CEPS in-depth analysis. INSPIRES CEPS, 2022; 1–57. [Google Scholar]
  146. Constantine, J.; Lie, J.; Liu, J.C. Recovery of rare earth elements from spent NiMH batteries using subcritical water extraction with citric acid. Journal of Environmental Chemical Engineering 2022, 10, 108000. [Google Scholar] [CrossRef]
  147. Yin, X.; Tian, X.; Wu, Y.; Zhang, Q.; Wang, W.; Li, B.; Gong, Y.; Zuo, T. Recycling rare earth elements from waste cathode ray tube phosphors: Experimental study and mechanism analysis. Journal of Cleaner Production 2018, 205, 58–66. [Google Scholar] [CrossRef]
  148. Wu, Y.; Yin, X.; Zhang, Q.; Wang, W.; Mu, X. The recycling of rare earths from waste tricolor phosphors in fluorescent lamps: A review of processes and technologies. Resources, Conservation and Recycling 2014, 88, 21–31. [Google Scholar] [CrossRef]
  149. Wang, J.-Z.; Hsieh, Y.-H.; Tang, Y.-C.; Shen, Y.-H. Separation of Cobalt, Samarium, Iron, and Copper in the Leaching Solution of Scrap Magnets. Metals 2023, 13, 90. [Google Scholar] [CrossRef]
  150. Patcharawit, T.; Kritsarikan, W.; Yingnakorn, T.; Khumkoa, S. Comparative Study of Manufacturing NdFeB Magnet Wastes Recycling: Oxidative Roasting-Selective Leaching and Whole Leaching Routes. Recycling 2022, 7, 68. [Google Scholar] [CrossRef]
  151. Lucey, P.; et al. Understanding the Lunar Surface and Space-Moon Interactions. Reviews in Mineralogy and Geochemistry 2006, 60, 83–219. [Google Scholar] [CrossRef]
  152. NASA. 2022 NASA's Centennial Challenges: Space Robotics Challenge, NationalAeronautics and Space Administration. Available online: https://www.nasa.gov/directorates/spacetech/centennial_challenges/space_robotics/about.html.
  153. Xu, F. The approach to sustainable space mining: issues, challenges, and solutions. IOP Conference Series: Materials Science and Engineering 2020, 738, 012014. [Google Scholar] [CrossRef]
  154. Elvis M, Krolikowski A, Milligan, T. Concentrated lunar resources: imminent implications for governance and justice. Phil. Trans. R. Soc. A 2021, 379, 20190563. [CrossRef] [PubMed]
Preprints 67940 g001
Figure 1. Illustrative view of different types of REE resources including the potential alternate future resources in light shaded, modified after [13].
Figure 1. Illustrative view of different types of REE resources including the potential alternate future resources in light shaded, modified after [13].
Preprints 67940 g001
Table 1. Overview of ΣREE range (µg/g) in marine sediments from different oceans (modified after Balaram, 2019).
Table 1. Overview of ΣREE range (µg/g) in marine sediments from different oceans (modified after Balaram, 2019).
Ocean Matrix ΣREE range (µg/g) Reference
East Siberian Arctic Shelf Bottom sediments 104 to 220 [44]
Central North Pacific Ocean Siliceous sediments 810.4 [46]
Afanasy Niktin Seamount (ANS) in the Eastern Equatorial Indian Ocean. Cobalt crust 1727 – 2511 [38,39]
Mid-Pacific seamount Cobalt-rich crusts 2085 [47]
Indian Ocean Ferromanganese crust 928 - 1570 [48]
Scotia Sea Ferromanganese crust 3400 [49]
Eastern South Pacific Deep sea mud 1000 – 2230 [50]
North Pacific (east & west of Hawaiian Islands) Deep sea mud 400 – 1000
Minamitorishima Island in the Western North Pacific REE-Rich Mud >1446.2 (REE+Y) [51]
South China Sea Ferromanganese nodule deposits 1460 (avg) [52]
Indian Ocean REY-rich mud > 400 [53]
Marine sediments 585 - 920
Andaman Sea, Indian Ocean Ferromanganese crust, summit of southern
seamount		 1139 [54]
Ferromanganese crust within the two peaks of the same seamount. 2285
Lakshadweep Sea, Indian Ocean Ferromanganese crust, La (200) & Y (150) [55]
West Sewell Ridge, Andaman Sea, Indian Ocean Ferromanganese crust 1600 [56]
Manganese nodules 1186
Clarion-Clipperton Fracture Zone,
North-eastern Pacific Ocean		 Deep-sea sediments >700 [57]
West Clarion–Clipperton Zone, Pacific Ocean Marine sediments 454.7 (REE+Y) [58]
North Pacific Ocean near Minamitorishima Island, Japan Deep-sea mud > 5,000 (REE+Y) [60]
Mid Pacific Ocean Fe-Mn nodules 1178 - 1434 [60]
Pacific Ocean Deep nodules 1326 [61]
Shallow nodules 1398
Pacific Ocean ocean-floor sediments 22,000 [62]
Table 2. Concentrations of REE in marine phosphorites and related rocks from different regions across the world.
Table 2. Concentrations of REE in marine phosphorites and related rocks from different regions across the world.
Ocean Phosphorites Average concentration (µg/g) Reference
Pacific and northeast Atlantic Seamount phosphorites 727 (∑REE+ Y) [40]
Continental margin phosphorites 161 (∑REE+ Y)
Doushantou Formation, South China Danzhai phosphorite deposit 21 to 447 (∑REE) [67]
Meishucun excavation sites, South China Cambrian phosphorites 99.1 - 709.7 (∑REE) [68]
Sedimentary Abu Tartur phosphate ore, Egypt Phosphate ore 0.05-0.20 wt. % (∑REE) [65]
Mississippian phosphorites, USA Phosphorite ore 18,000 (∑REE) [69]
Mountain
Pass phosphorites, USA		 Phosphorite ore
Chinese clay-type Phosphorite deposits Phosphorite ore 500 to 2000 (∑REE) [70]
Hazm Al-Jalamis Phosphorites, Saudi Arabia Phosphorites <121.8 (∑REE+ Y) [71]
Pabdeh Formation, Khormuj anticline, SW of Iran Phosphorites 48 to 682 ∑REE [72]
Northern African phosphorite deposits (Morocco, Algeria and Tunisia) 39.2 to 1759.4 ∑REE [66]
South China Phosphorus-bearing
dolomites		 330 ∑REY [73]
Phosphorus dolomites 676 ∑REY
Phosphorites 1477 ∑REY
Table 3. REE concentrations in stream sediments, river sediments, and lake sediments in different parts of the world.
Table 3. REE concentrations in stream sediments, river sediments, and lake sediments in different parts of the world.
Country Type of sediment ∑REE Reference
Indigirka River, in the Laptev Sea River sediments 124 to 197 [44]
Rhine river sediments, Europe Upper Rhine 136.07 [74]
Middle Rhine 215.32
Lower Rhine 340.45
Tributaries 291.39
Himalayan river system sediments Brahmaputra 95 [75]
Ganges 97
Megna 107
Padma 131
Jamuna 152
Yamuna 100
Rivers of the east coast of India Cauvery 171 [77]
Pennar 203
Krishna 131
Godavari-Vasista 194
Godavari-Gauthami 290
Mahanadi 270
Hooghly 167
South America Amazon sediments 217 [78]
The Mgoua watershed, Cameroon, Africa Sediments 282 to 728
Average 550		 [79]
China Stream sediments 212 [80]
Catchment sediments 187
Soils 190
Sri Lanka Lake sediments* 1011 [74]
Yellow River, China River sediment 149 [81]
Estuary 165
Laizhou Bay 173
* Lake sediments in the proximity of the Eppawala phosphate deposit in Sri Lanka. Sediment fraction (<63 μm) of each sample.
Table 4. Concentrations of rare earth elements in coal, and coal fly ash from different sources around the world.
Table 4. Concentrations of rare earth elements in coal, and coal fly ash from different sources around the world.
Place & Country Material ∑REE (µg/g) Reference
World average Fly ash 450 [93]
404 [84]
Poland Fly ash 101 - 543 [94]
Faer power plant in Guizhou Province, China Fly ash 240.20 to 520.27 [95]
lignite coal-based thermal power plants, India Fly ash 2100 [96]
Collie Basin, Western Australia Fly ash 0.21% ∑REO [35]
Pond Creek coalbed, Pike County, Kentucky, US Coal <300 to >1000 [87]
World hard coal Coal 69 [84]
World low-rank coal 65
World coal 68
US coal 62
China 138
South Korea Fly ash 267 to 556 [97]
Coal bed, Eastern Kentucky, US Fire clay 1965–4198 [98]
Qianxi coal-fired power plant, Guizhou province, China Fly ash 630.51 [73]
Thermal Power Station II (TS II) of Neyveli Lignite Corporation (NLC), Chennai, Tamil Nadu, India Fly ash 2160 (∑REE)
300 (Y)		 [99]
Central Appalachian Coal-Related Strata, West Virginia (WV) and Central Pennsylvania (PA), US WV MKT underclay 297 [100]
WV MKT coarse coal
refuse		 345
Central PA
LKT underclay		 221
Central PA
MKT underclay		 728
Table 5. REE concentrations (µg/g) of red mud from different countries in comparison with earth average crust composition, modified from [103].
Table 5. REE concentrations (µg/g) of red mud from different countries in comparison with earth average crust composition, modified from [103].
Location REE (µg/g)
La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb Y Sc
Average in Earth’s crust [108] 39 66 9 41 7 - 6 1 5 1 3 3 33 22
Chinalco, China [109] 416 842 95 341 64 - 56 184 48 25 28 28 266 158
Australia [110] - - - - - - - - - - - - 68 54
Brazil [111] - - - - - - - - - - - - 24 43
India [112] 110 70 0.5 - - - - - - - - - 1 5
India [113] 58 98 - - - - - - - - - - - 48
India [109] 112 191 18 48 9 - 7 - 4 - 1 2 13 58
Jamaica [114] 287 366 74 69 0 - 37 0 37 5 21 16 373 55
Greece [115] 114 386 28 98 21 - 22 - 16 4 13 4 75 121
Alumine de Greece, Greece [116] 130 480 29 107 19 - 22 3 20 4 13 13 108 -
Greece [117] 127 409 28 103 20 - 18 2 19 3 11 13 98 -
Greece [118] 149 418 26 115 29 5.0 23 - 1 4.3. 17 16 91.
Ajka, Hungary [119] 114 368 - - - - - - - - - - 68 -
Turkey [117] 169 480 47 161 32 - 4 26 23 4 13 14 113 -
Russian Federation [120] - - - - - - - - - - - - 53 25
Russian Federation [109] - - - - - - - - - - - - - 90
Iran [120] - - - - - - - - - - - - 1 19
Table 6. Concentrations of REE in mine tailings and mine waste of different mines, industrial materials, and industrial waste.
Table 6. Concentrations of REE in mine tailings and mine waste of different mines, industrial materials, and industrial waste.
Country Industrial waste ∑REE Reference
Poland Uranium mine tailings, Sudety region 64.9- 109.8 µg/g [106]
Southern Shanxi Province, China Low-grade bauxite 1539 µg/g [121]
Greece Bauxite 192 to 1109 (avg. 463) ΣREE + Y+Sc [122]
Australia Low–grade saprolite ore 1.14%
(∑REE oxides)		 [104]
Poland Metallurgical industry waste. >140 µg/g [107]
Malaysia Water Leach Purification (WLP) residue 88367 µg/g with Gd as the most abundant element [123]
Canada Red Mud 0.03 wt% [124]
Jamaica Red Mud >1303 (REE+Y+Sc) [114]
Alumine de Greece, Greece Red Mud >948 (REE+Y) [116]
Turkey Red Mud > 1086 (REE+Y) [117]
Sri Lanka Gem Mine 0.3% (∑REE oxides) [105]
Bagre-Nechí mining district, Colombia Mine waste (mostly gold mine residue and monazite waste) 2.19% (Ce, La, Nd & Pr) [125]
Russia Different types of red mud Sc (> 100 µg/g) [126]
Greece Bauxite residue (Red mud) 0.1% (∑REE+Y+Sc) [115]
Agios Nikolaos, Greece Bauxite residue ∑REE 260 & Sc 120 [127]
SARECO LLP, Kazakhstan Mineral formations (TMF) from the processing of phosphate uranium ores 5% [127]
Russia Phosphogypsum 0.43 - 0.52% [129]
Philippine Phosphogypsum 266 µg/g [130]
Table 7. Concentrations of REE in acid mine drainage (AMD) from different mines across the globe.
Table 7. Concentrations of REE in acid mine drainage (AMD) from different mines across the globe.
Name and location of the mine Type Concentration of ∑REE Reference
Minas Gerais, Brazil AMD 130 ng/ml [133]
Staszic post-mining, Poland Uranium mine 993.3 µg/ml [106]
Northern and Central Appalachian Coal Basins, US Coal mine 282 ng/ml [134,135]
Treated precipitate 517 µg/g
Coal mine, Treated AMD 724 µg/g
Central Appalachian AMD source, US Pregnant leach solution 132.02 µg/g
∑REE+Y+Sc		 [137]
Sao Domingo mining complex, Iberian Pyrite Belt, Portugal AMD <221.8 ng/ml [138]
Xingren coalfield, China AMD 118 to 926 ng/ml [139]
Table 8. Amounts of rare earth elements in different e-waste items.
Table 8. Amounts of rare earth elements in different e-waste items.
E-waste item REE Concentration per unit Reference
Nickel metal hydride (NiMH) battery ∑REE 5–25% [146]
Cathode-ray tube (CRT) phosphor (as a coating on the panel. ∑REE 1–7 g [147]
Fluorescent lamp ∑REE + Y 301.2 mg/1 g powder [148]
Cathode-ray tube (CRT) 265 mg/1 g powder
Navy submarines ∑REE 3636 kg [144]
Navy surface ships ∑REE 1818 kg
Lockheed-Martin F-35 ∑REE 416 kg
Toyota Prius ∑REE 15 kg
Air conditioner ∑REE 120 g
Mobile phone ∑REE 0.5 g
Wind turbine that generates 3.5 MW Electricity ∑REE 600 Kg [3]
Fly and bottom ash ∑REE 0.9-1.3% [10]
SmCo5 magnet Sm 21.94% [149]
NdFeB magnet Nd & Pr 64.5% & 17.32% [150]
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.
Copyright: This open access article is published under a Creative Commons CC BY 4.0 license, which permit the free download, distribution, and reuse, provided that the author and preprint are cited in any reuse.
Prerpints.org logo

Preprints.org is a free preprint server supported by MDPI in Basel, Switzerland.

facebook logotwitter logolinkedin logo
MDPI Initiatives
Important Links
Subscribe

Disclaimer

Terms of Use

Privacy Policy

© 2024 MDPI (Basel, Switzerland) unless otherwise stated