recovering rare earth metals from coal fly ashrecovering rare earth metals from coal fly ash author:...
TRANSCRIPT
Rec
ove
rin
g R
are
Eart
h
Met
als
fro
m C
oal
Fly
Ash
Ro
ss T
ag
ga
rt
De
pa
rtm
en
t o
f C
ivil
& E
nv
iro
nm
en
tal
En
gin
ee
rin
g
4 M
arc
h
20
15
1
2015
Wo
rld
of
Co
al A
sh (
WO
CA
) C
on
fere
nce
in N
asvh
ille,
TN
- M
ay 5
-7, 2
015
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p:/
/ww
w.f
lyas
h.in
fo/
Ou
tlin
eB
ackg
rou
nd
◦R
are
Eart
h E
lem
ents
◦C
oal
Fly
Ash
Ob
ject
ives
an
d H
ypo
thes
es
Res
earc
h A
pp
roac
h a
nd
Met
ho
ds
◦A
sh c
har
acte
riza
tio
n
◦Se
qu
enti
al e
xtra
ctio
ns
and
XA
S
◦Ex
trac
tio
n m
eth
od
s
Inte
llect
ual
Mer
it a
nd
Bro
ader
Imp
acts
2
Rar
e Ea
rth
Ele
men
tsC
on
sist
of
lan
than
ides
an
d y
ttri
um
No
t p
arti
cula
rly
rare
, ju
st d
iffu
se◦
10
3ti
mes
mo
re a
bu
nd
ant
than
pre
cio
us
met
als
◦C
rust
al c
on
cen
trat
ion
(2
20
pp
m)
com
par
able
to c
arb
on
(2
00
pp
m)
Hea
vy r
are
eart
hs
less
co
mm
on
3
Cri
tica
l Mat
eria
lsR
EE in
def
ense
, en
ergy
, an
d e
lect
ron
ics
ind
ust
ries
:◦
Gu
idan
ce/c
on
tro
l sys
tem
s
◦Pe
tro
leu
m c
rack
ing
cata
lyst
s
◦Pe
rman
en
t m
agn
ets
◦LE
Ds/
glas
s ad
dit
ive
◦M
oto
rs/g
ene
rato
rs
◦C
atal
ytic
co
nve
rter
s
◦Fl
at p
anel
dis
pla
ys
◦H
ard
dri
ves
◦B
atte
ries
◦H
ybri
d/e
lect
ric
veh
icle
s
4
REE
Cri
tica
lity
5
Cla
ssif
icat
ion
s fr
om
Se
red
in(2
01
0)
The
“Bal
ance
Pro
ble
m”
◦R
EE u
tilit
y d
oes
no
t m
atch
ab
un
dan
ce
◦Sh
ort
age
of
crit
ical
REE
Co
nve
nti
on
al o
res
hav
e lo
w C
/E r
atio
(o
utl
oo
k co
effi
cien
t)
Cat
ego
rySy
mb
ol
Nam
e
Cri
tica
l
Nd
Neo
dym
ium
EuEu
rop
ium
TbTe
rbiu
mD
yD
ysp
rosi
um
YYt
triu
mEr
Erb
ium
Un
crit
ical
LaLa
nth
anu
mP
rP
rase
od
ymiu
mSm
Sam
ariu
mG
dG
ado
liniu
m
Exce
ssiv
e
Ce
Cer
ium
Ho
Ho
lmiu
mTm
Thu
lium
YbYt
terb
ium
LuLu
teti
um
Rar
e Ea
rth
Pro
du
ctio
n
Du
an
d G
raed
el(2
01
1) a
nd
htt
p:/
/ww
w.c
net
.co
m/n
ews/
dig
gin
g-fo
r-ra
re-e
arth
s-th
e-m
ines
-wh
ere-
iph
on
es-a
re-b
orn
/
6
Sup
ply
an
d D
eman
d2
01
3:
86
%o
f R
EE p
rod
uct
ion
to
ok
pla
ce in
Ch
ina
Ch
ina
con
tro
ls 4
8%
of
glo
bal
REE
su
pp
ly
20
10
: d
eman
d e
xcee
ds
sup
ply
by
30
00
T
Dem
and
pro
ject
ed t
o in
crea
se c
on
sist
entl
y
7
Co
un
try
20
10
Pro
du
ctio
n (
t)2
01
1 P
rod
uct
ion
(t)
Esti
mat
ed
Re
serv
es
(t)
Ch
ina
13
0,0
00
13
0,0
00
55
,00
0,0
00
Un
ited
Sta
tes
0*
0*
13
,00
0,0
00
Res
t o
f w
orl
d3
,00
03
,00
04
2,0
00
,00
0
Tota
l1
33
,00
01
33
,00
01
10
,00
0,0
00
Ou
tlin
eB
ackg
rou
nd
◦R
are
Eart
h E
lem
ents
◦C
oal
Fly
Ash
Ob
ject
ives
an
d H
ypo
thes
es
Res
earc
h A
pp
roac
h a
nd
Met
ho
ds
◦A
sh c
har
acte
riza
tio
n
◦Se
qu
enti
al e
xtra
ctio
ns
and
XA
S
◦Ex
trac
tio
n m
eth
od
s
Inte
llect
ual
Mer
it a
nd
Bro
ader
Imp
acts
8
Envi
ron
men
tal H
azar
d5
3.4
mill
ion
to
ns
pro
du
ced
an
nu
ally
in t
he
U.S
.
Ove
r 4
0%
is r
ecyc
led
, pri
mar
ily in
cem
ent
The
rem
ain
ing
30
mill
ion
to
ns
is la
nd
fille
d o
r h
eld
in
wet
ash
imp
ou
nd
men
ts◦
Oft
en u
nlin
ed
◦P
ron
e to
fai
lure
Toxi
c tr
ace
ele
me
nts
: A
s, S
e, C
r, C
d, P
b, e
tc.
Co
nta
min
ate
gro
un
dw
ater
an
d s
urf
ace
wat
ers
9
Ash
Sp
ills
TVA
Kin
gsto
n F
oss
il P
lan
t in
D
ecem
ber
20
08
◦3
.7 m
illio
n m
3o
f m
ixed
fly
as
h a
nd
bo
tto
m a
sh r
elea
sed
◦3
00
acr
es c
on
tam
inat
ed
Dan
Riv
er (
Eden
, NC
) in
Fe
bru
ary
20
14
◦3
0,0
00
-39
,00
0 t
on
s o
f as
h
rele
ased
10
Stra
tegi
c M
etal
s in
Ash
Som
e as
hes
exc
ee
d o
re g
rad
e (
ove
r 1
00
0 m
g/k
g)
NIS
T SR
M 1
63
3b
has
42
0 m
g/k
g R
EE
Enri
ched
10
x d
uri
ng
com
bu
stio
n
Pre
ced
ent
for
met
al r
eco
very
fro
m c
oal
an
d f
ly a
sh◦
Ura
niu
m s
ou
rce
aft
er W
orl
d W
ar II
◦G
erm
aniu
m s
ou
rce
sin
ce 1
96
0s
◦A
lum
inu
m r
eco
very
res
earc
h in
19
70
s an
d 1
98
0s
◦R
ecen
t ga
lliu
m r
eco
very
fro
m f
ly a
sh
11
V.V
. Ser
edin
, S. D
ai /
Inte
rnat
ion
al J
ou
rnal
of
Co
al G
eo
logy
94
(2
01
2) 6
7–9
3
Ad
vant
ages
Reu
ses
a w
aste
pro
du
ct◦
Co
al w
ill b
e an
imp
ort
ant
ener
gy s
ou
rce
for
dec
ades
◦W
orl
dw
ide
sco
pe
No
exc
avat
ion
, ben
efic
iati
on
, an
d m
illin
g re
qu
ired
◦Id
eal f
orm
fo
r ch
emic
al p
roce
ssin
g
◦El
imin
ates
a m
ajo
r p
art
of
the
co
st a
nd
en
viro
nm
enta
l im
pac
t o
f R
EE p
rod
uct
ion
Nee
d f
or
add
itio
nal
min
es le
ss u
rgen
t◦
Tho
riu
m a
sso
ciat
ed w
ith
co
nve
nti
on
al o
res
12
Dis
adva
ntag
esR
EE s
epar
atio
n a
nd
pu
rifi
cati
on
sti
ll d
iffi
cult
◦En
ergy
an
d c
hem
ical
inte
nsi
ve
◦B
ased
larg
ely
in C
hin
a
Co
al a
sh h
as m
uch
low
er R
EE c
on
ten
t th
an
con
cen
trat
ed o
re
Met
als
entr
ain
ed w
ith
in a
sh p
arti
cles
Ash
co
mp
osi
tio
n h
eavi
ly d
epen
den
t o
n c
oal
ge
olo
gy
13
Res
earc
h O
bje
ctiv
es1
.C
har
acte
rize
REE
co
nte
nt
of
Am
eric
an f
ly a
shes
an
d c
orr
elat
e w
ith
ash
att
rib
ute
s
2.
Inve
stig
ate
stru
ctu
re a
nd
loca
tio
n o
f R
EE w
ith
in
fly
ash
usi
ng
seq
uen
tial
ext
ract
ion
s an
d X
AS
3.
Test
ind
ust
rial
ly-r
elev
ant
extr
acti
on
met
ho
ds,
q
uan
tify
ext
ract
able
REE
, an
d m
easu
re r
esid
ual
tr
ace
elem
ents
in f
ly a
sh a
fter
ext
ract
ion
14
Res
earc
h O
bje
ctiv
es1
.C
har
acte
rize
REE
co
nte
nt
of
Am
eri
can
fly
ash
es
and
co
rre
late
wit
h a
sh a
ttri
bu
tes
2.
Inve
stig
ate
stru
ctu
re a
nd
loca
tio
n o
f R
EE w
ith
in
fly
ash
usi
ng
seq
uen
tial
ext
ract
ion
s an
d X
AS
3.
Test
ind
ust
rial
ly-r
elev
ant
extr
acti
on
met
ho
ds,
q
uan
tify
ext
ract
able
REE
, an
d m
easu
re r
esid
ual
tr
ace
elem
ents
in f
ly a
sh a
fter
ext
ract
ion
15
Hyp
oth
eses
A.
Ap
pal
ach
ian
Bas
in c
oal
ash
es w
ill h
ave
hig
her
R
EE c
on
ten
t th
an Il
lino
is B
asin
or
Pow
der
Riv
er
Bas
in a
shes
.
B.
Na 2
O2
sin
teri
ng
will
be
as e
ffec
tive
as
HF
dig
esti
on
fo
r q
uan
tify
ing
REE
in f
ly a
sh. F
or
oth
er
elem
ents
, HF
dig
esti
on
will
be
mo
re a
ccu
rate
.
C.
REE
co
nte
nt
will
be
corr
elat
ed w
ith
BET
su
rfac
e ar
ea, p
arti
cle
size
, an
d m
ajo
r o
xid
e co
nte
nt.
16
Ash
Ch
arac
teri
zati
on
ALK
ALI
NE
SIN
TER
ING
Bak
e sa
mp
le in
Zr
cru
cib
le
wit
h s
od
ium
per
oxi
de
Leac
h w
ith
nit
ric
acid
USG
S m
eth
od
fo
r R
EE
anal
ysis
HF/
HN
O3
DIG
ESTI
ON
Wh
ole
ro
ck d
iges
tio
n
Evap
ora
te H
F an
d r
e-d
isso
lve
in n
itri
c ac
id
Qu
anti
fica
tio
n o
f m
etal
s re
mai
nin
g af
ter
extr
acti
on
17
Test
ch
arac
teri
zati
on
met
ho
ds
usi
ng
NIS
T SR
M
16
33
c as
a s
tan
dar
d
Det
erm
ine
REE
co
nce
ntr
atio
n in
co
al a
sh s
amp
les
Oth
er P
aram
eter
sO
bje
ctiv
e 1
:C
orr
elat
e as
h c
har
acte
rist
ics
wit
h t
ota
l an
d e
xtra
ctab
le R
EE d
ata
BET
su
rfac
e ar
ea◦
Mea
sure
gas
ad
sorp
tio
n
◦M
ore
po
rou
s fl
y as
h m
ay h
ave
hig
her
ext
ract
able
REE
co
nte
nt
rega
rdle
ss o
f p
arti
cle
size
An
alys
es a
lrea
dy
per
form
ed b
y C
AER
:◦
Maj
or
oxi
de
co
nte
nt
◦M
iner
alo
gy
◦A
sh c
on
ten
t o
f so
urc
e c
oal
18
Prel
imin
ary
Res
ult
s1
.H
F d
iges
tio
n a
nd
Na 2
O2
sin
teri
ng
are
accu
rate
q
uan
tifi
cati
on
met
ho
ds
2.
Man
y fl
y as
hes
co
nta
in 5
00
-60
0 p
pm
REE
3.
Cle
ar c
lust
erin
g b
y co
al b
asin
; Ap
pal
ach
ian
B
asin
ash
es s
eem
mo
st p
rom
isin
g
No
te: A
dd
itio
nal
ash
sam
ple
s w
ill b
e co
llect
ed
fro
m p
lan
ts in
th
e C
aro
linas
19
Prio
riti
zin
g A
shes
Co
al a
shes
co
mp
are
favo
rab
ly w
ith
REE
o
re d
epo
sits
20
V.V
. Ser
edin
, S. D
ai /
Inte
rnat
ion
al J
ou
rnal
of
Co
al G
eo
logy
94
(2
01
2) 6
7–9
3
Res
earc
h O
bje
ctiv
es1
.C
har
acte
rize
REE
co
nte
nt
of
Am
eric
an f
ly a
shes
an
d c
orr
elat
e w
ith
ash
att
rib
ute
s
2.
Inve
stig
ate
str
uct
ure
an
d lo
cati
on
of
REE
wit
hin
fl
y as
h u
sin
g se
qu
en
tial
ext
ract
ion
s an
d X
AS
3.
Test
ind
ust
rial
ly-r
elev
ant
extr
acti
on
met
ho
ds,
q
uan
tify
ext
ract
able
REE
, an
d m
easu
re r
esid
ual
tr
ace
elem
ents
in f
ly a
sh a
fter
ext
ract
ion
21
Hyp
oth
eses
D.
REE
will
be
entr
ain
ed in
th
e gl
assy
mat
rix
of
the
fly
ash
par
ticl
es r
ath
er t
han
su
rfac
e-b
ou
nd
. Th
e m
ajo
rity
of
the
REE
will
be
pre
sen
t in
th
e H
F-le
ach
able
fra
ctio
n o
f th
e as
h (
i.e. s
ilica
tes)
.
E.Th
e m
iner
al p
has
e o
f th
e ra
re e
arth
ele
men
ts in
fl
y as
h w
ill d
eter
min
e h
ow
eas
ily t
hey
can
be
extr
acte
d a
nd
wh
ich
aci
d is
mo
st e
ffec
tive
.
22
Seq
uen
tial
Ext
ract
ion
s4
g a
sh s
amp
le, 2
0 m
L o
f ex
trac
tan
t, 1
5 h
ou
rs
1.
Dei
on
ized
wat
er (
wat
er s
olu
ble
fra
ctio
n)
2.
1 M
am
mo
niu
m a
ceta
te (
ion
exc
han
geab
le)
3.
3 M
HC
l(ca
rbo
nat
e-b
ou
nd
)
4.
8.8
M H
2O
2an
d 4
M H
NO
3(o
xid
izab
le)
5.
1:1
mix
ture
of
HF
and
HN
O3
(sili
cate
-bo
un
d)
23
Ad
apte
d f
rom
Hu
ggin
s et
al.,
20
00
/ M
od
es o
f o
ccu
rren
ce o
f C
r in
fo
ur
US
coal
s
24
Yuan
, 20
09
/ L
each
ing
char
acte
rist
ics
of
met
als
in f
ly a
sh
X-ra
y M
eth
od
s
XA
NES
Nea
r-ed
ge (
±50
eV
)
Thre
e-d
imen
sio
nal
geo
met
ry
Co
ord
inat
ion
en
viro
nm
ent
Oxi
dat
ion
sta
te
EXA
FS
Exte
nd
ed
fin
e st
ruct
ure
(1
00
-10
00
eV
bey
on
d e
dge
)
Co
ord
inat
ion
en
viro
nm
ent
Nea
rest
nei
ghb
ori
ng
ato
ms
25
X-r
ay A
bso
rpti
on
Sp
ectr
osc
op
y (X
AS)
Req
uir
es s
ynch
rotr
on
rad
iati
on
so
urc
e
26
Par
son
s et
al.,
20
02
/ E
nvi
ron
men
tal a
nd
Bio
logi
cal A
pp
licat
ion
s o
f EX
AFS
an
d X
AN
ES S
pec
tro
sco
pie
s
Inte
rfer
ence
sA
bso
rpti
on
ed
ges
of
oth
er e
lem
ents
in s
amp
le m
ay
lie in
XA
NES
/EX
AFS
reg
ion
27
Bin
din
g e
ner
gy
(eV
)E
mis
sio
n (
eV)
No
.E
lem
.K
-ed
ge
LII
I-ed
ge
Kα1
Lα1
22
Ti
4966
4510.8
4504.9
23
V5465
4952.2
24
Cr
5989
5414.7
25
Mn
6539
5898.8
39
Y1
70
38
14
95
8.4
55
Cs
35985
5012
4619.8
56
Ba
37441
5247
4466.3
4827.5
57
La
38
92
55
48
33
34
41
.84
65
1.0
58
Ce
40
44
35
73
23
47
19
.74
84
0.2
60
Nd
43
56
96
20
83
73
61
.05
23
0.4
92
U17166
13614
Hu
ggin
s et
al.,
20
00
/ M
od
es o
f o
ccu
rren
ce o
f C
r in
fo
ur
US
coal
s
Yttr
ium
XA
SM
ost
pro
mis
ing
REE
◦Se
con
d m
ost
ab
un
dan
t (u
p t
o 1
00
mg
/kg)
◦N
o n
ota
ble
inte
rfer
ence
s
◦C
riti
cal R
EE
Ref
eren
ce m
ater
ials
sh
ou
ld m
imic
fly
ash
sam
ple
s (e
.g. y
ttri
um
min
eral
s em
bed
ded
in g
lass
)
Ob
ject
ive
2re
sult
s w
ill in
flu
ence
ext
ract
ion
m
eth
od
sel
ecti
on
in O
bje
ctiv
e 3
28
Go
od
arzi
and
Hu
ggin
s, 2
00
1 /
Sp
ecie
s o
f A
s, C
r, a
nd
Ni i
n m
illed
co
al, b
ott
om
ash
, an
d f
ly a
sh f
rom
a p
ow
er p
lan
t in
we
ster
n C
anad
a
Res
earc
h O
bje
ctiv
es1
.C
har
acte
rize
REE
co
nte
nt
of
Am
eric
an f
ly a
shes
an
d c
orr
elat
e w
ith
ash
att
rib
ute
s
2.
Inve
stig
ate
stru
ctu
re a
nd
loca
tio
n o
f R
EE w
ith
in
fly
ash
usi
ng
seq
uen
tial
ext
ract
ion
s an
d X
AS
3.
Test
ind
ust
rial
ly-r
ele
van
t ex
trac
tio
n m
eth
od
s,
qu
anti
fy e
xtra
ctab
le R
EE, a
nd
me
asu
re r
esi
du
al
trac
e e
lem
en
ts in
fly
ash
aft
er
extr
acti
on
29
Hyp
oth
eses
F.So
nic
atio
n o
r si
nte
rin
g o
f sa
mp
les
pri
or
to a
cid
d
iges
tio
n w
ill im
pro
ve R
EE r
eco
very
an
d e
nab
le
the
use
of
mo
re d
ilute
aci
ds.
G.
Rec
ove
rin
g R
EE f
rom
fly
ash
will
sim
ult
aneo
usl
y re
mo
ve t
he
maj
ori
ty o
f th
e le
ach
able
to
xic
elem
ents
(e.
g. A
s, S
e, C
r, P
b).
30
Init
ial M
eth
od
sD
irec
t A
cid
Lea
chin
g◦
8 M
HC
lat
10
5°C
for
2 h
ou
rs
Pre
ssu
re-D
iges
tio
n A
cid
Lea
ch◦
Pre
-tre
at w
ith
NaO
Hso
luti
on
at
20
0-2
45
°C
◦A
mb
ien
t te
mp
erat
ure
leac
h w
ith
12
.5 M
HC
l
Sulf
uri
c A
cid
Lea
chin
g◦
10
% v
/v H
2SO
4at
30
-80
°C f
or
2 h
ou
rs
◦Sp
ecif
ical
ly f
or
REE
in f
ly a
sh
31
Extr
acti
on
Var
iab
les
1.
Tem
per
atu
re (
25
-20
0°C
)
2.
Solid
-to
-liq
uid
rat
io (
up
to
1:2
)
3.
Aci
d t
ype
and
co
nce
ntr
atio
n
4.
Pre
trea
tmen
ts (
e.g.
sin
teri
ng)
5.
Du
rati
on
(3
0 m
inu
tes
to o
vern
igh
t)
32
Sint
erin
gC
on
vert
s m
iner
als
to a
cid
so
lub
le f
orm
s
Allo
ws
leac
hin
g w
ith
dilu
te a
cid
◦2
5%
HN
O3
afte
r si
nte
rin
g (O
bje
ctiv
e 1
)
◦Tw
ice
as e
ffec
tive
as
con
cen
trat
ed H
NO
3al
on
e
Var
iab
les
to b
e te
sted
:◦
CaO
and
FG
D w
aste
inst
ead
of
Na 2
O2
◦R
atio
of
flu
x to
sam
ple
◦Le
ach
ing
acid
an
d c
on
cen
trat
ion
33
Post
-Ext
ract
ion
Qu
anti
fy R
EE a
nd
tra
ce e
lem
ents
in r
emai
nin
g so
lids
◦Ev
apo
rate
aci
d
◦H
F d
iges
tio
n (
Ob
ject
ive
1)
Cal
cula
te e
xtra
ctio
n e
ffic
ien
cies
by
met
ho
d
Co
rrel
ate
ash
par
amet
ers
(Ob
ject
ive
1)
wit
h
extr
acti
on
eff
icie
ncy
34
Prel
imin
ary
Res
ult
sH
Cli
s th
e m
ost
eff
ecti
ve a
cid
Effe
cts
of
acid
an
d s
on
icat
ion
var
y co
nsi
der
ably
b
etw
een
sam
ple
s◦
May
dep
end
on
ash
ch
arac
teri
stic
s (O
bje
ctiv
e 1
)
◦H
igh
to
tal R
EE d
oes
no
t im
ply
hig
h e
xtra
ctab
le R
EE
Son
icat
ion
ap
pea
rs t
o h
ind
er R
EE r
eco
very
in
man
y ca
ses
(HC
lan
d H
NO
3)
◦In
con
sist
ent
resu
lts
for
H2SO
4
35
Prel
imin
ary
Res
ult
sH
Cli
s th
e m
ost
eff
ecti
ve a
cid
Effe
cts
of
acid
an
d s
on
icat
ion
var
y co
nsi
der
ably
b
etw
een
sam
ple
s◦
May
dep
end
on
ash
ch
arac
teri
stic
s (O
bje
ctiv
e 1
)
◦H
igh
to
tal R
EE d
oes
no
t im
ply
hig
h e
xtra
ctab
le R
EE
Son
icat
ion
ap
pea
rs t
o h
ind
er R
EE r
eco
very
in
man
y ca
ses
(HC
lan
d H
NO
3)
◦In
con
sist
ent
resu
lts
for
H2SO
4
36
Inte
llect
ual
Mer
itO
bje
ctiv
e 1
◦R
EE t
ota
ls f
or
bro
ad s
amp
le o
f A
mer
ican
fly
ash
es◦
Ash
par
amet
ers
linke
d t
o t
ota
l/ex
trac
tab
le R
EE
Ob
ject
ive
2◦
Use
of
XA
S to
exa
min
e R
EE in
fly
ash
◦B
ette
r u
nd
erst
and
ing
of
REE
str
uct
ure
in f
ly a
sh
Ob
ject
ive
3◦
Ap
plic
atio
n o
f re
leva
nt
extr
acti
on
met
ho
ds
to R
EE in
fl
y as
h
37
Bro
ader
Imp
acts
Envi
ron
men
tal
◦B
enef
icia
l reu
se o
f fl
y as
h◦
Red
uct
ion
in t
oxi
c tr
ace
elem
ents
Eco
no
mic
◦W
aste
mo
net
izat
ion
◦A
lter
nat
ive
sou
rce
for
cru
cial
REE
Nat
ion
al S
ecu
rity
◦St
able
do
mes
tic
sup
ply
of
stra
tegi
c m
etal
s◦
Co
nsi
der
ed c
riti
cal e
lem
ents
by
DO
E
38
Co
ncl
usi
on
Fly
ash
is a
pro
mis
ing
alte
rnat
ive
sou
rce
of
REE
Stro
ng
nee
d f
or
furt
her
res
earc
h o
n f
ly a
sh R
EE
con
ten
t, s
tru
ctu
re, a
nd
ext
ract
ion
Up
com
ing
wo
rk◦
Co
llect
ad
dit
ion
al a
sh s
amp
les
fro
m D
uke
En
ergy
an
d S
ante
e C
oo
per
◦B
egin
acq
uir
ing
XA
S st
and
ard
s
◦Se
qu
enti
al e
xtra
ctio
ns
39
Ack
no
wle
dge
men
tsTh
e H
su-K
im la
b
Dr.
Jam
es
C. H
ow
er
Dr.
Gar
y S.
Dw
yer
Osm
an U
lug
40
Ref
eren
ces
Lon
g, K
.R.,
20
11
, Th
e fu
ture
of
rare
ear
th e
lem
ents
; w
ill t
hes
e h
igh
-tec
h
ind
ust
ry e
lem
ents
co
nti
nu
e in
sh
ort
su
pp
ly?:
U.S
. Geo
logi
cal S
urv
ey
Op
en-F
ile R
epo
rt 2
01
1-1
18
9, 4
1 p
. [h
ttp
://p
ub
s.u
sgs.
go
v/o
f/2
01
1/1
18
9/]
.
Sch
wei
nfu
rth
, S.P
., 2
00
9, A
n in
tro
du
ctio
n t
o c
oal
qu
alit
y, in
Pie
rce,
B.S
.,
and
Den
nen
, K.O
., e
ds.
, Th
e N
atio
nal
Co
al R
eso
urc
e A
sses
smen
t O
verv
iew
: U.S
. Geo
logi
cal S
urv
ey P
rofe
ssio
nal
Pap
er 1
62
5–F
, C
hap
ter
C, 1
6 p
.
V.V.
Ser
edin
, S. D
ai /
Inte
rnat
ion
al J
ou
rnal
of
Co
al G
eolo
gy 9
4 (
20
12
) 6
7–
93
41