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Environmental Impacts of Metal and Other Inorganics on Soil and Groundwater in China
Published in P.M. Huang, I.K. Iskandar, M. Chino, T.B. Goh, P.H. Hsu, D.W. Oscarson, L.M. Shuman, Soils and Groundwater Pollution and Remediation, 2020
Rare earth elements are not only used widely in metallurgy, glass and ceramics making, petrochemical industry, and in production of luminous and magnetic materials, they also contribute to plant growth as well as yield and quality of the farm products (Guo, et al., 1988).
Recovery of Rare Earth Elements from Metallurgical Wastes
Published in Hossain Md Anawar, Vladimir Strezov, Abhilash, Sustainable and Economic Waste Management, 2019
Haque et al. [24] report on the crustal abundance, resource tonnage, and years of reserves estimates of REEs. Crustal abundances for REE are in the range of 0.48–68 ppm, and resource timeframes of 600 to 57,000 years of supply (Table 16.1). Resources have been calculated using data on the percentage of rare earths found in various ore deposits and the known resources of rare earth containing ores [24]. According to the U.S. Geological Survey (2017), the world resources of rare earth oxides are reported as 120 Mt. There are various metallic and metallurgical wastes that are considered suitable for REE extraction (Table 16.2). Rare earth elements (REEs) are important materials in numerous high-technology applications, but they have high supply risk, giving rise to the study of new sources. The recycling of REEs has been well researched, especially on a small scale, but it has not been widely implemented. Less than 1 percent of REEs were recycled in 2011 [10]. REEs occur in a large number of minerals in oxidic compounds, such as oxides, carbonates, phosphates and silicates, and are present as mixtures at 10 to 300 mg/kg concentrations in many rock formations, such as basalts, granites, gneisses, shales and silicate rocks [25]. The most abundant REE in the Earth's crust is cerium (Ce), at a concentration of 20 to 70 mg/kg, followed by neodymium (Nd) and lanthanum (La), with heavier REEs being less abundant [10]. REEs occur in nature in their oxidized forms in salts and minerals due to their electropositive nature and high affinity for oxygen.
Future Directions in Chemical and Biomolecular Engineering: A Few Examples
Published in Victor H. Edwards, Suzanne Shelley, Careers in Chemical and Biomolecular Engineering, 2018
Victor H. Edwards, Suzanne Shelley
The US EPA reports that e-waste currently accounts for about 2 percent of the solid waste stream, but that amount accounts for 70 percent of hazardous waste that is deposited in landfills. Importantly, electronic devices are a complex mixture of several hundred materials, including the rare earth elements. Thus, e-waste is rich in many toxic heavy metals, such as lead, mercury, cadmium, chromium, arsenic, and beryllium, which should not be released into the environment when the device is no longer needed.
Hydrometallurgical Roadmaps and Future Strategies for Recovery of Rare Earth Elements
Published in Mineral Processing and Extractive Metallurgy Review, 2023
C. Erust, M. K. Karacahan, T. Uysal
Rare earth elements are extracted from primary sources into aqueous solutions using the hydrometallurgical route, with different technologies available for leaching, which is an important part of rare earth processing. Physically beneficiated concentrates are leached in suitable reactants directly or after heat treatment (roasting or cracking) to dissolve metallic values. For the leaching of primary ores, water, inorganic acids, salts, bases, and organic acids are used as reagents. It can range from acid leaching with H₂SO₄, HCl, HNO₃ to NaCl or (NH₄)₂SO₄ or combined base and acid leaching. A comprehensive understanding of these processes is required in order to develop and implement more suitable methods for the recovery of rare earth metals (Jha et al. 2016; Marinela and Panayotov 2012).
Red Mud: Fundamentals and New Avenues for Utilization
Published in Mineral Processing and Extractive Metallurgy Review, 2021
The group of elements on the periodic table from atomic numbers 57 to 71 are considered as the rare earth elements. Scandium and yttrium are typically included in this category as well due to similarities in their chemical properties (Balaram 2019). The rare earth elements are widely applied in many new and developing technologies. The continuously high demand for rare earths has spurred a huge boom in their production and utilization over recent years. Applications for rare earth elements include a variety of things such as electronics, medicine, technology, and energy (Balaram 2019). It is clear that these elements are an integral part of our way of life and will continue to be as technology advance further. The issue with these elements is that they do not typically occur in deposits that are high enough in concentration to mine profitably. This is the reason that they were coined as rare earth elements. REES are found in more abundance in two types of deposits, alkaline igneous formations which include minerals like bastnaesite and residual deposits caused by excessive weathering effects including minerals like bauxite (Balaram 2019).
Release Characteristics of Manganese in Soil under Ion-absorbed Rare Earth Mining Conditions
Published in Soil and Sediment Contamination: An International Journal, 2020
Zuwen Liu, Chenbin Lu, Shi Yang, Jinfeng Zeng, Shiyun Yin
The rapid development of modern advanced technology has increased the demand for rare earth elements in the international market, especially medium and heavy rare earth elements with excellent physical properties (Dutta et al. 2016). Ion-absorbed rare earth ore belongs to China’s unique mineral resource, which is mainly distributed in the seven southern provinces and is the primary source of medium and heavy rare earth elements (Huang et al. 2015). More than 80% of the rare earth elements in ion-absorbed rare earth ore are adsorbed on the surface of clay minerals by ion-exchange phase (Chi et al. 2005). The traditional physical mining methods are not effective for the recovery of such resources, but when encountering with positive ions (such as Na+, NH4+, and H+) with the higher chemically activity, the adsorbed rare earth elements can be desorbed through ion exchange (Xiao et al. 2015). Based on this principle, ammonium sulfate leaching agent is usually used to recover rare earth elements by the in-situ leaching process in the current industry (Lai et al. 2018; Liu et al. 2018b).