Northeastern University Shenyang Scientists Propose Clean Rare Earth Chlorination Process

Highlights

• Chinese scientists propose a novel ‘clean rare earth chlorination’ process for sustainable rare earth element (REE) extraction.
• Electroconversion of chlorinated REEs offers environmental advantages over traditional extraction methods, including reduced chemical use and waste.
• Challenges in scaling and efficiency need to be addressed for widespread adoption of electrochemical REE processing techniques.

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 A group of physical scientists at the School of Metallurgy, Northeastern University (opens in a new tab), Shenyang, the capital and largest city of China’s northeast Liaoning Province recently had their paper published in the peer-reviewed journal Minerals Engineering, describing in detail the sources and application pathways involving rare earths, while updating the current research status involving rare earth extraction  as well as product preparation process and finally proposing a “clean rare earth chlorination” process.

Crucial inputs for industrial production across myriad industries deemed of national security interest for nations such as China, the authors provide a refresh on the traditional extraction processes such as concentrated sulfuric acid roasting, caustic soda decomposition and soda ash decomposition.

Raising concerns of high costs along with the strict criteria for raw material grade, the authors summarize the secondary wastes such methods produce, leading to varying degrees of environmental harm.

So, what are the primary processes involved with the production of rare earth elements?  The authors point to mostly:

Primary Rare Earth Production Processes	Summary
Precipitation	A chemical process where REEs are selectively separated from a solution by adding a specific chemical reagent, causing the REEs to form solid particles (precipitates) that can be collected and further purified, essentially “raining out” of the solution based on their chemical properties and the controlled pH level.
Hydrothermal processes	Hydrothermal processes are commonly used in the production and extraction of REEs, due to their ability to dissolve, transport, and precipitate metals under high-temperature and high-pressure conditions. These processes occur naturally in geological environments but are also harnessed in industrial applications to extract rare earth elements from minerals
Sol–gel processes	A versatile chemical method widely used for synthesizing advanced materials, including those involving REEs.  This process enables the formation of metal oxides or other complex compounds from a liquid phase through the transition of a solution (sol) into a gel-like network (gel), which is then dried and heat-treated to obtain a desired material. In the context of rare earth element processing, the sol-gel method is highly effective for producing high-purity, homogenous rare earth oxides and ceramics used in various high-tech applications.
Spray pyrolysis processes	Spray pyrolysis is a versatile and efficient method for producing fine powders and thin films, particularly useful in the synthesis of REE minerals such as rare earth oxides, phosphors, and catalysts. This process involves atomizing a precursor solution into fine droplets, which are then carried by a gas and heated to induce pyrolysis (thermal decomposition), resulting in the formation of solid particles or thin films.

As readers undoubtedly understand, high cost and high energy use remain of paramount concern.

Given the significance of rare earth resources and sustainable industrial development, the authors’ express the mission-critical nature of the identification of an effective recovery and clean manufacturing method for rare earth ores.

Upon reviewing the principles and application status of existing processes, the authors view the challenge from two lens: A)  the extraction of transmitted rare earths and B) the preparation of rare earth products.

The authors of this paper, again affiliated with Northeastern University, both propose a novel technology for the electrochemical conversion of chlorinated rare earths and rare earth chlorine and analyze, as well as analyze its feasibility from a technical perspective.

What’s the mission of the Chinese authors? 

They propose an environmentally sustainable new process concerning the electroconversion of chlorinated rare earth elements based on the idea of environmentally sustainable development. This review summarizes the benefits and drawbacks of the current rare earth extraction and production methods used in rare earth mining, as well as the current application status of these methods.

So, what’s the status of use of electroconversion of chlorinated REEs based on principles of environmentally sustainable development?  This is a relatively emerging area of research.

Electroconversion refers to the use of electrochemical methods to convert one chemical form into another, often with the goal of reducing energy consumption, waste, and environmental impact.

In the context of REEs, this process could be applied to convert chlorinated REE compounds into more usable forms, such as oxides of metals, in a cleaner, more sustainable way.

What follows is a brief breakdown of the elements involved.

Starting with electrochemical processing of rare earth elements, electrochemical processes, including electrowinning (opens in a new tab) and electrorefining (opens in a new tab).), are already used in the metallurgy of various elements, including rare earths.

In theory, these methods can be applied to chlorinated REE compounds to accomplish A) the extraction of rare earth metals directly from chlorides or convert them into oxides and B) use less energy and fewer reagents, which can lower overall carbon emissions and waste.

For example, rare earth chlorides, like lanthanum chloride (LaCl₃) or neodymium chloride (NdCl₃), could potentially undergo electrolysis to recover the rare earth metals.

So, what are some environmental advances of this approach?

The electrochemical conversion of chlorinated rare earths, when compared to traditional methods such as hydrometallurgy (leaching with strong acids), offers several advantages from an environmentally sustainable development perspective. Rare Earth Exchanges includes some of these advantages in the table below.

Advantages	Summary
Reduction of Harmful Chemicals	Traditional methods for processing REEs often involve large quantities of acids and alkalis, leading to significant waste and environmental pollution. Electrochemical processes could significantly reduce or eliminate the need for hazardous chemicals
Energy Efficiency	Electrochemical processes can be more energy-efficient than high-temperature pyrometallurgical methods (e.g., smelting), which require extensive energy input. Renewable energy sources (solar, wind) can further enhance the sustainability of these electrochemical processes
Minimization of Waste	Electroconversion could produce fewer toxic byproducts, particularly chlorinated gases like chlorine or hydrochloric acid, compared to traditional chemical processes. Any chlorine gas generated could be safely captured and reused in other industrial processes, promoting a circular economy approach.

But challenges ensue as well. Plus, some considerations when reviewing this unfolding set of topics.  While electroconversion offers significant potential, there are also challenges that need to be addressed for it to become a widely adopted, sustainable practice in the rare earth industry.

Challenges/Points	Summary
Electrolyte Design	The electrolyte in electrochemical cells for chlorinated rare earths must be carefully selected. It should be stable, non-toxic, and effective at conducting ions to enable efficient electroconversion of REEs.
Efficiency and Selectivity	Electrochemical processes may struggle with low efficiencies or poor selectivity between different rare earth elements, especially when dealing with complex mixtures of chlorinated compounds. Research into catalyst design and electrochemical cell optimization will be important for improving these aspects.
Scalability	While electrochemical processes can be sustainable and environmentally friendly on a laboratory scale, scaling them up for industrial-level rare earth extraction or recycling will require significant advancements in technology and infrastructure.
Economic Feasibility	The cost of setting up electrochemical systems may be higher initially compared to traditional methods, though the long-term benefits in terms of energy savings, reduced waste, and environmental compliance could offset these costs.

How can electrochemical conversion methods be applied to recycle rare earths?

Electrochemical conversion methods could also be applied to recycle rare earths from waste products like electronic devices (e-waste) and magnets. In this scenario, chlorinated rare earths could be recovered and purified using electrochemical methods, reducing the need for environmentally damaging mining processes. This is particularly important given the critical nature of rare earth elements in high-tech industries and their limited global supply.

Some examples of potentially sustainable electrochemical approaches to REEs include molten salt electrolysis (opens in a new tab), a technique that is used to extract rare earth metals from their chlorides. It’s energy-efficient and produces fewer harmful emissions compared to traditional smelting. It could be optimized further using renewable energy to make the process even more sustainable.

Also there is a process known as electrodeposition (opens in a new tab). Rare earth metals can be deposited from aqueous or non-aqueous solutions of rare earth chlorides, potentially eliminating the need for high-temperature smelting. Advances in electrode materials and electrochemical reactor designs could make this approach more viable.

Company Examples

Several companies are researching electroconversion and related sustainable technologies for REE processing as the industry seeks to reduce environmental impact and reliance on traditional methods.

Some examples include ReElement Technologies. (opens in a new tab) In collaboration with https://www.purdue.edu/ (opens in a new tab) is developing innovative technologies for REE separation and purification. Their methods use less power and water while producing near-zero waste. They are scaling up operations in Indiana with the goal of providing sustainable alternatives for REE separation at a commercial scale.

Meanwhile MP Materials, a key player in U.S. rare earth production, is working to expand its processing capabilities. With backing from the U.S. Department of Defense, they are enhancing their Mountain Pass facility to commercially separate and refine light and heavy rare earth elements, which would reduce dependence on overseas facilities, particularly in China.

Finally, Lynas Rare Earths (opens in a new tab), an Australian company, has also received significant U.S. government support to build a rare earth separation facility in Texas. This facility aims to create a more resilient and environmentally responsible REE supply chain for the U.S.  Undoubtedly all sorts of groups in China are looking as well.

Conclusion

It is feasible to pursue the electroconversion of chlorinated rare earth elements as part of an environmentally sustainable development strategy?  Such processes can potentially reduce the environmental impact of rare earth extraction and refining by using less harmful chemicals, minimizing waste, and leveraging renewable energy. However, challenges related to process efficiency, selectivity, and scalability need to be addressed through further research and development to make these methods economically viable on a large scale.

A team from the School of Metallurgy, Northeastern University (opens in a new tab) Shenyang  proposes a novel clean rare earth chlorination” process published in the peer-reviewed journal Minerals Engineering. (opens in a new tab)