(705d) Analysis of Twenty Coal Ashes for Rare Earth Element Content Using Inductively Coupled Plasma Mass Spectrometry (ICP-M)

Rare earths elements (REE) are widely employed in magnets, electronics, phosphors, metal

alloys, glasses, batteries, computer hard drives, automobile emission and petroleum refinery catalysts,

and sorbents, with adequate substitutions often unavailable. Unfortunately there have been concerns

with the supply and environmental issues associated with the mining and production of REE from ores in

the U.S. and around the world. Therefore, already mined and processed secondary sources of REE are

of interest. Coal ash is seen as a possible source for REEs since the U.S. produces over one hundred

million tons of ash from coal-fired power plants annually, and some coals and coal ashes have been

shown to have relatively high concentrations of REEs. Additionally, it is also important to determine the

concentration of critical or more valuable rare earth elements, since many of the elements are in good

supply.

In this study twenty coal ash samples were analyzed for total rare earth content, individual REE

concentrations, as well as percent critical REE. These data were compared to data reported on the

NETL EDX website, and uncertainties in the data are discussed. All of the ashes studied were reported

to have at least 500ppm total REE content based on the EDX website data on a whole sample basis (i.e.

no further ashing was conducted). Other trace elements were also analyzed to see any association with

the REE as well as identify any other valuable elements that may be economically co-extracted. Results

of the REE amount and uncertainties in coal fly ash and bottom ash are discussed.