Penn State Scientists Devise Green Method To Extract Rare Earths

A new method improves the extraction and separation of rare earth elements—a group of 17 elements critical for technologies such as smartphones and electric car batteries—from unconventional sources.

Photo Insert: Joseph Cotruvo Jr., assistant professor and Louis Martarano Career Development Professor of Chemistry at Penn State, a member of Penn State's Center for Critical Minerals, and co-corresponding authors of the study

New research led by scientists at Penn State and the Lawrence Livermore National Laboratory (LLNL) demonstrates how a protein isolated from bacteria can provide a more environmentally friendly way to extract these metals and to separate them from other metals and from each other.

The method could eventually be scaled up to help develop a domestic supply of rare earth metals from industrial waste and electronics due to be recycled.

"In order to meet the increasing demand for rare earth elements for use in emerging clean energy technologies, we need to address several challenges in the supply chain," said Joseph Cotruvo Jr., assistant professor and Louis Martarano Career Development Professor of Chemistry at Penn State, a member of Penn State's Center for Critical Minerals, and co-corresponding authors of the study.

"This includes improving the efficiency and alleviating the environmental burden of the extraction and separation processes for these metals. In this study, we demonstrate a promising new method using a natural protein that could be scaled up to extract and separate rare earth elements from low-grade sources, including industrial wastes."

The new method takes advantage of a bacterial protein called lanmodulin, previously discovered by the research team, that is almost a billion times better at binding to rare earth elements than to other metals.

A paper describing the process appears online on Oct. 8 in the journal ACS Central Science. The protein is first immobilized onto tiny beads within a column—a vertical tube commonly used in industrial processes—to which the liquid source material is added.

The protein then binds to the rare earth elements in the sample, which allows only the rare earths to be retained in the column and the remaining liquid drained off.

Then, by changing the conditions, for example by changing the acidity or adding additional ingredients, the metals unbind from the protein and can be drained and collected. By carefully changing the conditions in sequence, individual rare earth elements could be separated.

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