Toward a More Sustainable Future for the Rare Earths Industry
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2024-10-15
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Rare earth elements (REEs) are a set of metallic elements. Cast your mind back to high school chemistry and they are the obscure and difficult-to-pronounce elements near the bottom of the periodic table. They comprise 15 elements in the lanthanoid series plus scandium and yttrium.A new book in the Special Publications series, Rare Earth Elements: Sustainable Recovery, Processing, and Purification, describes sources of rare earths and methods of production that have the potential to make recovery, processing, and purification more sustainable. We asked the book’s editors about developments in the rare earths industry and the latest techniques and technologies.The names of these elements—such as praseodymium, dysprosium, and ytterbium—might not be part of your everyday conversation but they are definitely part of your everyday life. REEs are essential components of more than 200 products, especially high-tech consumer products, such as cellular telephones, computer hard drives, electric and hybrid vehicles, and flat-screen monitors and televisions. For example, headphone technologies and the ability to design them smaller is possible because of strong neodymium magnets in them.There are many other uses beyond household items, for example in defense equipment and technologies such as electronic displays, guidance systems, lasers, and radar and sonar systems.What quantity of REEs are needed for all these applications?The amount of each element used in these different applications and devices is actually very small compared to the total weight, volume, or value of the product. However, when you multiply the tiny amount needed for each device by the number of devices globally, the quantity required is significant—and growing.How do you think demand for rare earths will change over time and why?Demand for rare earths depends on many technological, industry, market, and geopolitical factors but it will definitely increase.Demand for rare earths depends on many technological, industry, market, and geopolitical factors but it will definitely increase. For example, the small and powerful rare-earth magnets that rely on the elements neodymium, praseodymium, and dysprosium are essential in the most efficient electric motors, which in turn are essential for electrification and the energy transition. Many industries beyond magnets will continue to rely heavily on rare earths.Current projections indicate that their demand will increase by 3 to 7 times the existing demand in the next couple of decades. Key drivers for this trajectory are the new energy transition strategies and decarbonization efforts around the globe, which are driving the development of and increasing reliance on renewable technologies, all of which require higher use of REEs.This book explores the recovery, processing, and purification of rare earths. Can you briefly describe these steps?The exact steps in producing rare earths vary from source to source. In general, recovery refers to extracting rare earths from their original medium or state—including ore, mining tailings, manufacturing wastes, or end-of-life materials—to render them available in solution. At this stage, rare earths are collected as a mixture, which needs to be upgraded.Processing of these mixtures takes place by using various technologies, including solid phase extraction, bioseparation, and others, which generate a high-value stream of REEs low in impurities, and in many cases individual elements.Finally, purification means upgrading separated rare earths into high-purity forms that can be sold to manufacturers, such as magnet makers and catalyst manufacturers. How have recent technologies made these processes more sustainable?REE mine tailings contain processing chemicals, salts, and radioactive materials. Tailings are particularly problematic in REE mining because of the significant waste-to-yield ratio. For every ton of REEs that is produced, there are 2,000 tons of mine tailings, including 1 to 1.4 tons of radioactive waste.Technology development will enhance conventional sources of rare earths, as well as unlock unconventional sources at mines, from manufacturing wastes, and in end-of-life products—in ways that adequately protect the natural environment and human health. High-volume industrial wastes or process tails have long been known to contain considerable quantities of REEs. However, the economics of recovering these materials have always been limited by their dilute nature in the waste, often found in parts per million concentrations, which required large volumes of consumables when using conventional hydrometallurgical processes.New technologies are being developed that can overcome limitations by improving the selectivity of the extractive processes and enabling high rates of reagent recycle.New technologies are being developed that can overcome these limitations by improving the selectivity of the extractive processes and enabling high rates of reagent recycle. Where conventional deposits are not found globally and supply depends on additional sources, exploitation of abundant industrial byproducts using these novel technologies can provide a stable supply for REEs.What are potential new sources of rare earths?There are two categories of potential new sources: via conventional mining, such as ores, and above ground mining, such as waste streams.Historically, almost all rare earth production has come from only three types of minerals: bastnaesite (a fluoro-carbonate mineral), monazite (a phosphate mineral), and ion-adsorbed clay minerals. However, rare earths are contained in other mineral forms, such as silicates, and a number of process innovations have the potential to unlock these other mineralogical forms and dramatically increase the number and geographic distribution of potential rare earth sources.Rare earths can also be found in a number of production waste streams, such as from coal production and coal-fired electricity generation, and from bauxite processing, which is used in the production of aluminum. End-of-life products, such as hard disk drives from server farms are another potential new source of rare earths. There is a considerable amount of research underway to develop processes that will lower the costs and reduce the environmental impacts of recovering rare earths from these waste sources.How might the industry’s methods, techniques, or technologies evolve over the next 10 years?Over the next 10 years, rare earths will be recovered from a wider range of sources than at present—including more countries, more mineralogical forms, and more waste streams and end-of-life products. At the same time, significant efforts are being made to find substitutes for REEs in some applications, and to some extent this has been achieved. We are likely to see further developments in this respect.It is expected that the REE industry will reach a modernization period, characterized and driven primarily by increased digitization, social responsibility, use of renewables, use of robotics, and artificial intelligence, as well as internal pressure for structural adjustment (as market demand for commodities changes), shortage of talent, geopolitical tensions and development of regional supply chains. How is this book organized, and for whom is it written?The book is organized around nine chapters. The first chapter provides an overview of the global rare earths industry, including production, international trade, and prices.The next three chapters discuss the potential for producing rare earths from three specific unconventional resources: coal fly ash, the residue left over after burning coal for electricity generation; residue from the processing of bauxite, the mined raw material from which aluminum is produced; and process waste streams from the mining of phosphate rock and production of phosphoric acid, the source of phosphorus in fertilizers.The final five chapters discuss innovative approaches to the recovery, processing and purification of rare earths: new approaches to solvent extraction in aqueous solutions, separation of rare earths by crystallization, aqueous electrochemical processing; beneficiation using biotechnological approaches, and adsorption-based separation and recovery of rare earths.This book is intended for science and engineering students, researchers, and industry practitioners who are interested in finding out more about new sources of rare earths and ways of processing them that can be deployed in response to increasing demand.
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