Chemical Engineering January 2019 - 7

Chementator
Recovering rare-earth elements from coal
byproducts
University of Kentucky
A
team from the University
of
Kentucky
1. Preparation
(Lexington, Ky.; www.
uky.edu) and Virginia
Polytechnic Institute (Blacksburg,
Va.; www.vt.edu) has set
up a novel pilot plant to recover
rare-earth elements (REEs)
from coal-based sources, aiming
to produce high-grade REE
concentrates from coal-based
leachate. Byproducts of coal
mining are a promising source
for highly in-demand REEs, says
Rick Honaker, professor of mining
engineering at the University
of Kentucky. " All of the REEs,
including scandium and yttrium, are present
in coal, whereas most other sources contain
only a select number of REEs, " he explains.
Leaching conditions from coal sources
X-ray
sorter
Qualified
feedstock
Rare earth mineral
(REM)/alkaline
mineral
recovery
Thickener
Process
water
2. Separation
Ball
mill
Sieve
screen
Impact
mill
REE
Miconizer
Decarbonization/
coal recovery
product
Dry
coal
Crackling
(external/
off-site)
REM
filter
REM
product
Residue
filter
3. Leaching
require milder sulfuric-acid concentrations
than leaching from other mineral sources,
but the low REE composition in the leachate
(<100 parts per million; ppm), along with
the high concentration of contaminant ions,
including iron, magnesium, aluminum, calcium
and others, requires a rigorous solventextraction
and scrubbing circuit designed by
the team specifically for handling coal-based
resources. Prior to solvent extraction, the
leachate is chemically reduced to convert
Fe3+ to Fe2+ ions using ascorbic acid, which
enables effective rejection of iron ions in the
solvent-extraction circuit.
The pilot plant utilizes a sorting technology
based on dual X-ray transmission to efA
research
team from the University
of New South Wales
(Sydney, Australia; www.unsw.
edu.au) and Ruhr-Universität
Bochum (Bochum, Germany; www.
ruhr-universität-bochum.de) has succeeded
in transferring structural characteristics
of natural enzymes to metallic
nanoparticles, achieving high
catalytic activity.
In the case of enzymes, the reacting
substances must pass through
a channel from the surrounding solution
to the active enzyme center,
where the structure provides favorable
reaction conditions. To mimic enzyme
structures, the team proposed
nanoparticles with etched substrate
fectively extract higher-grade REE content.
" The material extracted by the sorter is more
leachable than other portions of the material, "
explains Honaker. The pilot plant has
produced concentrates containing greater
than 99% total REEs from coarse coal refuse
material, coal-based mine acid water and
precipitate waste material generated from
the treatment of mine acid water.
The 0.25-ton/h pilot plant is currently the
world's largest unit focused on REE recovery
and concentration from coal sources, and
with funding from the U.S. Department of Energy
(DOE), the team is currently designing a
20-ton/h commercial plant utilizing this technology.
According to Honaker, this commercial
plant would likely produce three different
REE concentrations: 99% scandium; a mixture
of neodymium, praseodymium and dysprosium
(Nd-Pr-Dy); and an yttrium product.
A catalyst that mimics enzymes
channels. The team first produced
nanoparticles (10-nm dia.) of nickel
and platinum. The nickel is then removed
by chemical etching to form
channels. An oleylamine (a long-chain
unsaturated fatty amine) is used as
a capping layer that blocks the external
surface of the nanoparticles
participating in the catalytic reaction.
Finally, the active centers on the particle
surface are deactivated to ensure
that only the active centers within the
channels participate in the reactions.
Using the oxygen-reduction reaction
as a model reaction (an important
step in fuel-cell operation), the
catalytic activity of these channeled
particles were compared to those of
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
JANUARY 2019
conventional particles having active
centers only on the surface. It was
observed that the oxygen reaction
occurs mainly within the etched channels,
which provide a nanoconfined
reaction volume different from the bulk
electrolyte conditions. Active centers
in the channels catalyze the reactions
three times more efficiently than active
centers on the particle surfaces,
showing the potential of nanozymes.
The team plans to extend the concept
to other reactions, such as
electrocatalytic CO2 reduction. The
researchers believe the concept will
make energy conversion processes
more efficient using electricity generated
from renewable sources.
7
Waste
Two-stage
acid
leaching
To
wastewater
treatment
REE filter
4. Extraction/precipitation
Selective
precipitation
Oxalate
precipitation
Waste
Solvent extraction/
scrubbing/stripping
Edited by:
Gerald Ondrey
RENEWABLE JET FUEL
At the end of last October,
euglena Co. (Tokyo, Japan;
www.euglena.jp) completed
the construction of Japan's
first demonstration plant for
the production of renewable
jet and diesel fuel in Yokohama.
The $58-million pilot
plant, located at the company's
Yokohama site, has
a production capacity of 5
barrels per day (bbl/d; about
125,000 L/yr) of renewable
liquid fuels, using the Biofuels
Isoconversion Process
(BIC). Euglena expects to
supply a next-generation
renewable diesel fuel this
summer, and to achieve revenue-generating
flights with
renewable jet fuel in 2020.
On this project, euglena is
collaborating with the City of
Yokohama, Chiyoda Corp.,
Itochu Enex Co., Isuzu Motors
Ltd., ANA Holdings Inc.,
and Hiroshima Council for
the Promotion of Collaboration
between Government,
Academia and the Automobile
Industry.
The demonstration plant will
begin full-scale operation in
spring 2019 and begin producing
renewable jet and
diesel fuel using Euglena,
(Continues on p. 8)
http://www.uky.edu http://www.euglena.jp http://www.vt.edu http://www.unsw http://www.edu.au http://WWW.CHEMENGONLINE.COM
Chemical Engineering January 2019

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