New sensor detects valuable rare earth element terbium from non-
traditional sources
Low concentrations could be identified from acid mine drainage and other
waste sources

Date:
August 25, 2021
Source:
Penn State
Summary:
A new luminescent sensor can detect terbium, a valuable rare earth
element used in smart phone displays, from complex environmental
samples like acid mine waste.



FULL STORY ==========================================================================
A new luminescent sensor can detect terbium, a valuable rare earth
element, from complex environmental samples like acid mine waste. The
sensor, developed by researchers at Penn State, takes advantage of a
protein that very specifically binds to rare earth elements and could
be harnessed to help develop a domestic supply of these metals, which
are used in technologies such as smart phones, electric car batteries,
and energy efficient lighting. A paper describing the sensor appears
Aug. 25 in the Journal of the American Chemical Society.


========================================================================== Terbium, one of the rarest of the rare earth elements, produces the green
color in cell phone displays and is also used in high-efficiency lighting
and solid- state devices. However, there are a variety of chemical, environmental, and political challenges to obtaining terbium and other
rare earth elements from the environment. Developing new sources of
these metals also requires robust detection methods, which poses another challenge. For example, the gold standard method of detecting rare earth elements in a sample -- a type of mass spectrometry called ICP-MS --
is expensive and not portable. Portable methods, however, are not as
sensitive and do not perform well in complex environmental samples,
where acidic conditions and other metals can interfere with detection.

"There is not currently a domestic supply chain of rare earth elements
like terbium, but they are actually quite abundant in non-traditional
sources in the U.S., including coal byproducts, acid mine drainage,
and electronic waste," 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 senior
author of the study. "In this study, we developed a luminescence-based
sensor that can be used to detect and even quantify low concentrations of terbium in complex acidic samples." The new sensor relies on lanmodulin,
a protein that the researchers previously discovered that is almost a
billion times better at binding to rare earth elements than to other
metals. The protein's selectivity to bind rare earth elements is ideal
for a sensor, as it is most likely to bind to rare earths instead of
other metals that are common in environmental samples.

To optimize lanmodulin as a sensor for terbium specifically, the
researchers altered the protein by adding the amino acid tryptophan to
the protein.

"Tryptophan is what is called a 'sensitizer' for terbium, which means
that light absorbed by tryptophan can be passed to the terbium, which the terbium then emits at a different wavelength," said Cotruvo. "The green
color of this emission is actually one of the main reasons terbium is
used in technologies like smart phone displays. For our purposes, when
the tryptophan-lanmodulin compound binds to terbium, we can observe
the emitted light, or luminescence, to measure the concentration of
terbium in the sample." The researchers developed many variants of the tryptophan-lanmodulin sensor, optimizing the location of the tryptophan
so that it does not interfere with lanmodulin's ability to bind to
rare earth elements. These variants provided important insights into
the key features of the protein that enable it to bind rare earths with
such high selectivity. Then, they tested the most promising variant to determine the lowest concentration of terbium the sensor could detect
in idealized conditions -- with no other metals to interfere. Even
under highly acidic conditions, like that found in acid mine drainage,
the sensor could detect environmentally relevant levels of terbium.

"One challenge with extracting rare earth elements is that you have
to get them out of the rock," said Cotruvo. "With acid mine drainage,
nature has already done that for us, but looking for the rare earths is
like finding a needle in a haystack. We have existing infrastructure
to treat acid mine drainage sites at both active and inactive mines
to mitigate their environmental impact. If we can identify the sites
with the most valuable rare earth elements using sensors, we can better
focus extraction efforts to turn waste streams into revenue sources."
Next, the researchers tested the sensor in actual samples from an acid
mine drainage treatment facility in Pennsylvania, an acidic sample with
many other metals present and very low levels of terbium -- 3 parts
per billion. The sensor determined a concentration of terbium in the
sample that was comparable what they detected with the "gold standard"
method, suggesting that the new sensor is a viable way to detect low concentrations of terbium in complex environmental samples.

"We plan to further optimize the sensor so that it is even more
sensitive and can be used more easily," said Cotruvo. "We also hope
to target other specific rare earth elements with this approach." ========================================================================== Story Source: Materials provided by Penn_State. Original written by Gail McCormick. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Emily R. Featherston, Edward J. Issertell, Joseph
A. Cotruvo. Probing
Lanmodulin's Lanthanide Recognition via Sensitized Luminescence
Yields a Platform for Quantification of Terbium in Acid Mine
Drainage. Journal of the American Chemical Society, 2021; DOI:
10.1021/jacs.1c06360 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210825185351.htm

--- up 15 weeks, 5 days, 22 hours, 45 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)