Science & Technology

Sustainably mining rare earth elements from fertilizer by-products

Penn State University engineers are granting a National Science Foundation to recover rare earth elements from phosphorus gypsum, a fertilizer by-product that is stored indefinitely in open dumps and pumped into designated lakes, as shown here. I received.

Despite its name, rare earth elements are not so rare in practice. NS 17 metal elements It is ubiquitous in nature and is becoming more common in technology as an important component such as microchips. The “rare” description is about how difficult it is to extract into a usable format. The usual techniques for extracting them from complex minerals are usually energy intensive, producing significant carbon emissions, and most of the rare earth elements are lost in waste from other industrial processes.

To develop a more sustainable process for recovering rare earth elements from phosphorus plaster, a by-product of fertilizer production, researchers at Penn State University have been working for four years as part of a collaborative study with Case Western Reserve University and Clemson University. Was awarded a National Science Foundation grant of $ 571,658. $ 1.7 million in funding. Each university is independently funded to pursue certain aspects of the project, but the project is centrally coordinated by Case Western Reserve researchers. Lauren Greenlee, an associate professor of chemical engineering, is leading the work of Penn State University with Rui Shi, an assistant professor of chemical engineering.

“Today, an estimated 200,000 tonnes of rare earth elements are trapped in untreated phosphorus gypsum waste in Florida alone,” said Greenlee, who pipes phosphorus gypsum into ditches and ponds for indefinite storage. I explained that it was sent. “This source of rare earth elements is currently undeveloped due to the challenges associated with radioactive species and the difficulty of separating individual elements. The vision of this project is valuable for rare earth elements, fertilizers, clean water, etc. Discovering new separation mechanisms, materials and processes for recovering resources from the waste stream of the fertilizer industry, paving the way for a sustainable domestic supply of rare earth elements, and a sustainable agricultural sector. “

Greenlee also said that the United States relies heavily on international sources for its supply of rare earth elements. COVID-19 (New Coronavirus Infection) The pandemic caused a long delay in the supply chain.

“This is a serious problem exacerbated by the economic, environmental and safety complications of obtaining and using rare earth elements internationally,” says Greenlee.

Phosphate ore is formed when phosphate rock is processed into fertilizer and contains a small amount of naturally occurring radioactive elements such as uranium and thorium. Due to this radioactivity, by-products are stored indefinitely, and improper storage can pollute soil, water, and air. To harvest rare earth elements trapped in phosphorus gypsum, researchers propose a multi-step process using engineered peptides that can accurately identify and separate rare earth elements through a special membrane.

“Individual rare earth elements have similar sizes and formal charges, so traditional membrane separation mechanisms are inadequate,” says Greenlee. “The key technical goal of this study is to discover the mechanisms that underpin the selectivity of peptide ions and to leverage those mechanisms to design a new class of highly selective membranes.”

Christine Duval, a researcher at Case Western Reserve, a senior researcher and assistant professor of chemical engineering, and Julie Renner, a co-principal researcher and assistant professor of chemistry and biomolecular engineering, will develop molecules that latch on specific rare earth elements. .. Their designs are guided by computational modeling work by Rachel Getman, Principal Investigator and Associate Professor of Chemistry and Biomolecular Engineering at Clemson. Once the peptide was developed, Greenlee investigated how it would work in aqueous solution, and Shi used system analysis tools such as technological economic analysis and life cycle assessment to address the proposed rare earth elements to the environment. Assess impact and economic feasibility-recovery system under various design and operating conditions.

“What is the overall sustainability impact of this process?” She asked. “We want to be more sustainable away from the current environmental impacts. By translating basic research and laboratory-scale results into system-level environmental and economic impacts, we want to do that. It can be achieved. Then, sustainability results can be integrated into the design to guide future research goals while advancing rare earth element recovery and phosphorus gypsum treatment. “

The proposed project complements other studies at Pennsylvania State University. Naturally occurring protein molecules Extract grouped rare earth elements from other industrial waste sources.

“Our project hypothesizes that the water molecules associated with peptides that bind to rare earth elements can be rearranged and that rearrangement can be controlled more efficiently based on individual rare earth elements,” Greenlee said. Mr. says. X-ray absorption spectroscopy is used to study interactions at the atomic level to see how molecules exchange atoms as they bond. “By modeling and experimenting, we continue to iterate to ensure that we understand how the molecules work together.”

Sustainably mining rare earth elements from fertilizer by-products Sustainably mining rare earth elements from fertilizer by-products

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