Notes on Contributions to the Science of Rare Earth Element Enrichment in Coal and Coal Combustion Byproducts

Abstract

Coal and coal combustion byproducts can have significant concentrations of lanthanides (rare earth elements). Rare earths are vital in the production of modern electronics and optics, among other uses. Enrichment in coals may have been a function of a number of processes, with contributions from volcanic ash falls being among the most significant mechanisms. In this paper, we discuss some of the important coal-based deposits in China and the US and critique classification systems used to evaluate the relative value of the rare earth concentrations and the distribution of the elements within the coals and coal combustion byproducts.

Leaching Process of Rare Earth Elements, Gallium and Niobium in a Coal-Bearing Strata-Hosted Rare Metal Deposit—A Case Study from the Late Permian Tuff in the Zhongliangshan Mine, Chongqing

“…Furthermore, with respect to the increasing challenges of global warming and other environmental issues, the utilization of coal resources is increasingly encouraged to be economically effective and environmentally benign [2,3]. Hence, some coal-bearing strata have been regarded as promising alternative sources for rare metals recovery, to which many researchers around the world have paid great attention in recent years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. There are already some precedents in the case of rare metal extraction from coal and coal-related materials.…”

“…For example, germanium is currently being recovered mainly from three well-known Ge-bearing coal deposits, namely Lincang (Yunnan province) and Wulantuga (Inner Mongolia) of China, as well as Spetzugli of eastern Russia, which account for more than 50% of the total yearly production of Ge metal in the world [3,7,9,11]. The discovery of a super-large coal-hosted gallium and aluminum deposit in the Jungar Coalfield (Inner Mongolia), China is another example [16], which was highly recognized and considered as the third most significant and outstanding discovery for coal-hosted metal deposit production following the successful industrial extractions of uranium and germanium from coal [5,17]. Recently, a new type of Nb (Ta)-Zr (Hf)-REE-Ga polymetallic ore deposit was discovered in the late Permian coal-bearing strata of eastern Yunnan, southwestern China [14], and some other types of elemental assemblages have also been observed in coalfields in southern China [7,8,18,19].…”

“…The term "metalliferous coal" has been widely adopted to describe coal anomalously enriched in trace metals with potential economic and practical value for rare metal recovery [1][2][3][4][5][6][7][8][9][10][11]. From the perspective of industrial production, coal can be considered as metalliferous at the level of trace element concentrations being at least 10 times greater than the corresponding averages of world coal [1].…”

“…However, extraction techniques directly related to the recovery of rare metals from coal deposits, which are undoubtedly the critical issue for metalliferous coal uses, have been paid less attention in the literature. At present, the possible recovery of rare metal elements from coal-bearing strata and coal combustion products (CCPs) is an exciting research area, since coal and particularly its combustion derivations may have elevated concentrations of metal elements that are comparable to or even higher than those found in conventional metal ores [5,[20][21][22][23][24][25][26][27]. For this reason, the U.S. Department of Energy's National Energy Technology Laboratory (NETL) funded 10 projects in 2015 aiming to support the lab's research program on the recovery of REE from coal and coal byproducts [28].…”

China’s Rare Earths Supply Forecast in 2025: A Dynamic Computable General Equilibrium Analysis

“…They have special chemical, catalytic, electrical, magnetic, and optical properties and are, therefore, widely used in traditional sectors, including agriculture, petrochemicals, metallurgy, and textiles, as well as in strategic emerging industries such as hybrid cars and wind turbines [1][2][3]. Due to their role in domestic industrial development and economic growth, there is a growing demand for rare earths in many countries.…”