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13

APRIL Issue

Earth Elements

Institute, which has already built a successful pilot plant and

has got the process well on its way to commercialization.

“I want to see every one of these routes be successful in order

to create a domestic supply chain,” Ziemkiewicz says. “Our next

project – the one that we’re just starting now with DOE [the U.S.

Department of Energy], we will build a roughly half-ton-a-year

processing facility, and that will take acid mine drainage and

create a pre-concentrate that we will then turn into a high-grade

mixed rare earth oxide on site.”

In Kentucky, Honaker says the pilot plant built to extract rare

earth elements from coal refuse has also been a success,

demonstrating the production of a highly concentrated rare

earth oxide from refuse with minimal processing cost – and the

processing is not overly complex.

“We pull out the coarse refuse that has the high [concentration

of] rare earths, grind it down to 1 mm, then we heat the material

up to decompose the mineral that contains rare earths, and

then we put it into a leach system using sulfuric acid to extract

the rare earths in solution,” he says. “Then we use a few

stages of selective precipitation, and that’s how we produce the

concentrations.”

Honaker says a survey of coal processing plants shows there

are enough REEs in the waste stream of just a fraction of the

coal processing plants currently operating in the US to meet

current demand for REEs.

“I believe that the resource in coal is real,” he says. “We have

proven that you can extract the rare earths and produce a high-

quality product.”

The extraction of REEs from coal ash is the most complex of

the three, but Massachusetts-based Physical Sciences Inc.

has developed a process to accomplish this and has also

developed a pilot-scale project. Research facilities around the

country have been involved in the effort on research to extract

REEs from coal-based sources – both public and private, both

inside and outside of coal-producing regions.

One thing that makes the idea look so promising is the fact

that the processing of waste for REEs can be done as an add-

on to existing processes. With acid mine drainage it’s an add-

on to existing water treatment, which removes the elements

along with pollutants, creating a sludge that can be processed

for recovery of REEs. With coal refuse, it’s an add-on to coal

processing itself – and one potentially capable of accepting

stored waste as well as the current waste stream.

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