biological iron and sulfate control in mining waters
TRANSCRIPT
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Biological iron and sulfate control in mining
waters
Jaakko Puhakka
Tampere University of Technology
Comprehensive sulfate management in cold mining waters, Oulu, March 21, 2018
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Objectives
• To develop an integrated process comprising
a fluidized-bed reactor (FBR) and a gravity
settler for precipitative removal of iron and
sulfate from bioleach liquors
1. Partial removal from bioleaching circuits
2. Removal from bioleaching effluent streams
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FBR configuration
Fluidized-bed reactors for iron
oxidation at TUT
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Various biomass carriers used in FBR’s
Various biomass carriers:
• Activated carbon (=AC)
• Diatomaceous earth (Celite)
• Al2O3 (Compalox)
• Jarosite flocculated with
InChem flock D 33
Criteria for carrier selection:
• Biomass hold-up capacity
• Chemical and mechanical
durability
• Iron-oxidation rates
• Material costs
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Bacterial communities developing on the
carrier materials (DGGE)
“Ferrimicrobium acidophilum”
(99-100 % similarity)
No readable sequence
data obtained
Leptospirillum ferriphilum
(99-100 % similarity)
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Process developed for iron and
sulfate control
1
2
5
6
7
3
4
9
7
8
1: Feed pump
2: FBR
3: Base addition
4: Settling tank
5: Aeration pump
6: Aeration unit
7: Recycle pump
8: System effluent
9: Precipitate removal(Not drawn to the scale)
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7
Feed solution:
• Barren heap bioleaching
solution from which
valuable metals (Cu, Zn, Ni
and Co) had been
recovered
• Initial pH ~3
• Initial redox ~200-340 mV
• Initial Fe2+ ~6-8 g/L
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Removal of excess iron from
bioleach circuit liquors
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0
3
6
9
12
0 25 50 75 100 125
HR
T, h
Time, day
0.7
9
5 5
2.51.5
1 1.5
0
3
6
9
12
0 25 50 75 100 125
Fe
2+, g
/L
Time, day
0
1
2
3
4
5
0 25 50 75 100 125
pH
Time, d
a
b
c
pH
0
3
6
9
12
0 25 50 75 100 125
HR
T, h
Time, day
0.7
9
5 5
2.51.5
1 1.5
0
3
6
9
12
0 25 50 75 100 125
Fe
2+, g
/L
Time, day
0
1
2
3
4
5
0 25 50 75 100 125
pH
Time, d
a
b
c
pH
0 25 50 75 100 125
Time, d
FBR performance at various HRTs
2.5
1.0
0.7
9.0
1.5
5.01.5
5.0
Feed: ○
FBR effluent:
HRT
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0
20
40
60
80
100
0
4
8
12
16
20
0 25 50 75 100 125O
xid
atio
n, %
g F
e2+/L
·h
Time, day
0
2
4
6
8
0 25 50 75 100 125
DO
2, m
g/L
Time, day
0
10
20
30
40
0 25 50 75 100 125
kg
O2/m
3. d
ay
Time, day
400
500
600
700
0 25 50 75 100 125
Re
do
x, m
V
Time, d
|
5.0
2.5
1.5 1.0
1.59.0
5.0
0.7
HRT, h
a
b
c
d
| || | | | | |
Iro
n o
xid
atio
n ra
te,
Oxyg
en
tra
nsfe
r ra
te,
Dis
so
lve
d o
xyg
en
,R
ed
ox, m
V
0 25 50 75 100 125
Time, d
FBR performance at various HRTs
● Rate
○ Efficiency (%)
HRT, h
0 25 50 75 100 125Time, day
400
500
600
700
0 25 50 75 100 125
Time, d
Re
do
x, m
V
2.5
1.0
0.7
9.0
1.5
5.01.5
5.0
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Precipitation of iron in the gravity settler
at different FBR HRTs
0
5
10
15
20
25
30
0 25 50 75 100 125
Iro
n p
reci
pita
tion
, mg
/L·h
Time, d
5.0 2.5
1.5
1.0
1.5
9.0
5.0
0.7
HRT, h
a
| | || | | | | |
0
20
40
60
0 25 50 75 100 125
Pre
cip
itate
d p
erc
en
t, %
Time, d
b
Partial removal of iron from
bioleach circuits
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12
Removal of iron and sulfate from
bioleaching effluent streams
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Operational conditions during the
experimental periods with pH adjustment
pH 2.5 pH 3.0 pH 3.5 pH 3.2 pH 3.0 pH 2.8 pH 2.8
pH adjustment with KOH pH adjustment with CaCO3
1 65432 7
6.01.5 g Fe2+/L in the feed
0 30 60 90 120 150
Time, d
140.5 g Fe2+/L in
the feed
HRT = 2 h HRT = 2 hHRT = 5 h
pH 3
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Feed and effluent Fe2+ concentrations
during the pH adjustment
Feed
Effluent
Fe2+ , g/L
0
4
8
12
16
0 30 60 90 120 150
KOH
2.5 3.0 3.5 3.2 3.0 2.8 2.8
CaCO3
Time, d
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0
4
8
12
16
0 30 60 90 120 150
Fe
2+, g
/L
Time, day
0
200
400
600
800
0 30 60 90 120 150
Re
do
x p
ote
ntia
l, m
V
Time, day
0
2
4
6
8
10
0 30 60 90 120 150
DO
, m
g/L
Time, day
0
20
40
60
80
100
0
2
4
6
8
10
0 30 60 90 120 150
Oxid
atio
n
eff
icie
ncy,
%
Iro
n o
xid
atio
n ra
te,
g F
e2+/L
·h
Time, day
0
20
40
60
80
100
0
10
20
30
40
50
60
0 30 60 90 120 150
Pre
cip
ita
tio
n
eff
icie
ncy,
%
Iro
n p
recip
ita
tio
n ra
te,
g/L
·h
Time, d
KOH
2.5 3.0 3.5 3.2 3.0 2.8 2.8
CaCO3
a
b
d
c
e
Iron oxidation and precipitation rates
and efficiencies
KOH CaCO3
pH 2.5 3.0 3.5 3.2 3.0 2.8 2.8
Rates
Efficiencies
m
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Sulfate concentration in the FBR feed, effluent, and
precipitated sulfate, and precipitated mol ratio of
[Fe]:[S]
FBR feed
Effluent
Precipitated sulfate
Theoretical mol ratio of [Fe]:[S] of
pure jarosite with the idealized
formula of XFe3(SO4)2(OH)6,
where X = Na+, K+, NH4+ or H3O
+
0
20
40
60
0 30 60 90 120 150
SO
42- , g
/L
Time, day
KOH CaCO3
a
b
0
1
2
3
4
5
0 30 60 90 120 150
Pre
cip
ita
ted
[Fe
/S]
b
Time, d
KOH CaCO3
pH 2.5 3.0 3.5 3.2 3.0 2.8 2.8
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An X-ray diffractogram of precipitate from
gravity settler without pH adjustment
All peaks with labeled d-values (in Å) represent Na- and H3O-jarosites
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18
Precipitates - pH adjustment with KOH
pH 2 2.5 2.5-3.0 3.0 3.0-3.5 3.5
Jarosite, hydronian
(K,H3O) Fe3(SO4)2(OH)6
Natro jarosite,
NaFe3(SO4)2(OH)6
Goethite (a-FeOOH)
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19
Precipitates - pH adjustment with CaCO3
Brushite CaPO3(OH)2H2OJarosite, hydronian
(K,H3O) Fe3(SO4)2(OH)6
Jarosite synthetic
KFe3(SO4)2(OH)6
pH 3.2 3.0 2.8 2.8
15 g Fe2+ / L
Gypsum
(CaSO4·2H2O)
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Conclusions
The integrated process consisting of an FBR combined with
a gravity settler in the recycle line can be applied for:
1) Iron control (partial removal) in bioleaching applications
to prevent the accumulation of dissolved iron in leaching
circuits. The process can be optimized for efficient and
high-rate iron regeneration
2) Treatment of bioleaching effluents for high-rate and
high-efficiency iron and sulfate removal as stable end
products