Raffinate Neutralization Experiments at the McClean Lake Mill – Removal of Arsenic and Nickel
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Raffinate Neutralization Raffinate Neutralization Experiments at the McClean Lake Experiments at the McClean Lake Mill – Mill – Removal of Arsenic and Nickel Removal of Arsenic and Nickel John Mahoney Hydrologic Consultants, Inc., 143 Union Blvd., Suite 525, Lakewood, Colorado, USA Donald Langmuir Hydrochem Systems Corp., Denver, Colorado, USA Maynard Slaughter Crystal Research Laboratories, Greeley, Colorado, USA John Rowson COGEMA Resources, Saskatoon, Saskatchewan, Canada
description
Raffinate Neutralization Experiments at the McClean Lake Mill – Removal of Arsenic and Nickel. John Mahoney Hydrologic Consultants, Inc., 143 Union Blvd., Suite 525, Lakewood, Colorado, USA Donald Langmuir Hydrochem Systems Corp., Denver, Colorado, USA - PowerPoint PPT Presentation
Transcript of Raffinate Neutralization Experiments at the McClean Lake Mill – Removal of Arsenic and Nickel
Raffinate Neutralization Raffinate Neutralization Experiments at the McClean Lake Experiments at the McClean Lake
Mill –Mill –Removal of Arsenic and NickelRemoval of Arsenic and Nickel
John Mahoney Hydrologic Consultants, Inc.,
143 Union Blvd., Suite 525, Lakewood, Colorado, USA
Donald Langmuir Hydrochem Systems Corp., Denver, Colorado, USA
Maynard SlaughterCrystal Research Laboratories, Greeley, Colorado, USA
John RowsonCOGEMA Resources, Saskatoon, Saskatchewan, Canada
Location MapLocation Map
OverviewOverview
Arsenic and Nickel Bearing Uranium OresArsenic and Nickel Bearing Uranium Ores
Tailings disposal issuesTailings disposal issues
Raffinate 300-700 mg/L As, 200-500 mg/L Ni, Raffinate 300-700 mg/L As, 200-500 mg/L Ni, pH~1.0pH~1.0
Diffusion of As into Fox Lake required As and Diffusion of As into Fox Lake required As and Ni in tailings pore waters be ~ 1 mg/LNi in tailings pore waters be ~ 1 mg/L
Mill and JEB TMFMill and JEB TMF
Tailings Disposal SystemTailings Disposal System
Tailings Optimization and Tailings Optimization and Validation Validation
License Application - Initial model based on License Application - Initial model based on mineral precipitation (scorodite) and surface mineral precipitation (scorodite) and surface complexation of As on Hydrous Ferric Oxide complexation of As on Hydrous Ferric Oxide (Langmuir et al., 1999)(Langmuir et al., 1999)
Demonstrated that As < 1 mg/L was possibleDemonstrated that As < 1 mg/L was possible
Tailings Optimization and Validation Program Tailings Optimization and Validation Program (TOVP) ongoing studies to (TOVP) ongoing studies to Verify and improve process, Verify and improve process, Monitor tailings management facility, andMonitor tailings management facility, and Validate model assumptionsValidate model assumptions
Tailings NeutralizationTailings Neutralization
Tailings neutralization circuit increases Fe:As > 3Tailings neutralization circuit increases Fe:As > 3
Ferric sulfate is used to increase Fe:AsFerric sulfate is used to increase Fe:As
Neutralization by slaked limeNeutralization by slaked lime
Two stage process Two stage process pH 4 first tank pH 4 first tank pH 7 - 8 second tankpH 7 - 8 second tank
Tailings Neutralization CircuitTailings Neutralization Circuit
to TMF
24 hour metallurgical composite sample
Raffinate Tailings BaCl 2
Fe 2 (SO 4 ) 3
CaO (pH 4)
pH pH
THICKENER
NEUTRALIZATION TANKS
Flocculant
CaO (pH 8)
MIXING TANK
Process Air
Raffinate Neutralization Raffinate Neutralization ExperimentsExperiments
Plant raffinate spiked ~ 700 mg/L As, 500 mg/L Plant raffinate spiked ~ 700 mg/L As, 500 mg/L NiNi Ferric sulfate addedFerric sulfate added Dry Lime (CaO), slaked lime (Ca(OH)Dry Lime (CaO), slaked lime (Ca(OH)22, or NaOH, or NaOH Some experiments included leach residueSome experiments included leach residue Short duration to simulate residence times in Short duration to simulate residence times in
Neutralization CircuitNeutralization Circuit Filtered samples - solution analysesFiltered samples - solution analyses Solids air dried -Solids air dried - mineralogical analysismineralogical analysis
Raffinate 2 series, RedoxRaffinate 2 series, Redox measurements, measurements, single beaker experimentssingle beaker experiments
SetupSetup
Raffinate CompositionsRaffinate Compositions (mg/L)(mg/L)
Parameter Raffinate 1 Unspiked
Raffinate 1
Raffinate 2 Raffinate 2
Unspiked
pH 1.5 1.1
Total As 362 732 (920) 693 (729)
Sum of As (III+V) 351 668
As(III) 100 447
As (V) 251 221
Fe Total 629 2,400 (2,700) 808 1,854 (2,400)
Fe (II) 640 685
Al 420 200
Ca 760 589
Na 48 23
Sulfate 14,100 21,430
Ni 203 560 (550) 230 515 (529)
Eh (mv) 668
Fe/As NA 4.4 NA 3.6
Neutralization Tests at pH Values of Neutralization Tests at pH Values of 2.2 to 7.4 (right to left) Beaker on Far 2.2 to 7.4 (right to left) Beaker on Far
Left is Slurried Lime)Left is Slurried Lime)
Samples 9-27-5 and 6Samples 9-27-5 and 6
Filter Cake WetFilter Cake Wet
Mineralogy StudiesMineralogy Studies
X-ray diffraction SEM with Energy Dispersive Spectrometry Chemical analysis, mainly XRF, Fe(II) EXAFS- Canadian Light Source and Argonne APL Microprobe (electron beam, synchronous
radiation) Quantitative mineralogy - XRD, analysis
Single Beaker TestsSingle Beaker Tests
Raffinate 2 Separated mineral precipitates rather than
accumulate all precipitates Enhanced X-ray diffraction determinations Initial volume of solution ~ 5 L Three solution samples collected Four solid samples
Single Beaker ExperimentSingle Beaker Experiment
Single Beaker, #1 First Filter Single Beaker, #1 First Filter CakeCake
Single Beaker #4 Wet ProductSingle Beaker #4 Wet Product
Arsenic Concentrations as Function Arsenic Concentrations as Function of pHof pH
0.01
0.1
1
10
100
1000
0 1 2 3 4 5 6 7 8 9
pH before filtering
As
(m
g/L
)
Raffinate 1 Raff 1 Ca(OH)2 No Residue Raff 1 Na(OH) No Residue
Raff 1 Slaked Lime Leach Residue Raff 1 Na(OH) Leach Residue Raff 1 Slaked Lime No Residue
Raffinate 2 Raff 2 Slaked Lime No Residue Raff 2 Slaked Lime Single Beaker
Raffinates
Nickel RemovalNickel Removal
0
100
200
300
400
500
600
0 1 2 3 4 5 6 7 8 9
pH before filtering
Ni
(mg
/L)
Raffinate 1 Raff 1 Ca(OH)2 No Residue Raff 1 Na(OH) No Residue
Raff 1 Slaked Lime Leach Residue Raff 1 Na(OH) Leach Residue Raff 1 Slaked Lime No Residue
Raffinate 2 Raff 2 Slaked Lime No Residue Raff 2 Slaked Lime Single Beaker
Raffinates
Solution ConcentrationsSolution Concentrations
Concentrations of Major Components for Slaked Lime Neutralization of Raffinate 2
0.001
0.010
0.100
1.000
10.000
100.000
1,000.000
10,000.000
100,000.000
0 1 2 3 4 5 6 7 8
pH before filtering
Co
nc
en
tra
tio
n (
mg
/L)
Total As Total Fe Al Si Sulfate Ni
SB As SB Fe SB Al SB Si SB Sulfate SB Ni
Raffinate 2
SB-2
SB-3
SB-4
Molar Amounts Removed from Molar Amounts Removed from SolutionSolution
Raffinate 2Raffinate 2Comparison with Residual
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
Spikedraffinate
Sample 9-27-1
Sample 9-27-2
Sample 9-27-3
Sample 9-27-4
Sample 9-27-5
Sample 9-27-6
Remains inSolution
Sample
Mo
les
As Fe Ni Fe(II)
pH = 2.18
pH = 3.23pH = 4.09
pH = 5.29
pH = 6.24
pH = 7.32
Saturation IndicesSaturation Indices(based upon As (V) and Fe(III) concentrations)(based upon As (V) and Fe(III) concentrations)
-20
-15
-10
-5
0
5
0 1 2 3 4 5 6 7 8
pH
Sa
tura
tio
n In
de
x
Gypsum Ni(OH)2 Ni3(AsO4)2:8H2O Ferrihydrite Scorodite-cr Scorodite-am
Annabergite
Theophrastite
Ferrihydrite
Amorphous Scorodite
Gypsum
Crystalline Scorodite
Ion Activity ProductsIon Activity Products
-45.0
-40.0
-35.0
-30.0
-25.0
-20.0
0.00 2.00 4.00 6.00 8.00
pH
IAP
Scorodite
Ferrihydrite
Eh-pH diagram for the systems Fe – As – O – H based upon Eh-pH diagram for the systems Fe – As – O – H based upon stabilities of scorodite and ferrihydrite using speciatedstabilities of scorodite and ferrihydrite using speciated
As and Fe data from the Raffinate 2 neutralization As and Fe data from the Raffinate 2 neutralization experimentsexperiments
-1
-0.5
0
0.5
1
1.5
0 2 4 6 8 10
pH
Eh
(v)
Fe2+
Fe3+
Scorodite-log K = 23.97
H 2O(l)
H2O(l)
O 2 (g)
H2(g)
25°C
Ferrihydrite- log K = 33.33
Geochemical ModelGeochemical Model PHREEQCPHREEQC used used
Ferric arsenate complexes included in database Ferric arsenate complexes included in database Disequilibrium steps included to explain removal of Disequilibrium steps included to explain removal of
Ni at low pHNi at low pH Force fitForce fit
Simple mineral precipitation reactionsSimple mineral precipitation reactions
Gypsum – Sulfate [CaSOGypsum – Sulfate [CaSO4 4 • • 2H2H22O]O]
Scorodite (Ksp adjusted) – Fe and AsScorodite (Ksp adjusted) – Fe and As to pH to pH ~5~5 [FeAsO [FeAsO4 4 • •
2H2H22O]O]
Ferrihydrite/Green Rust II- IronFerrihydrite/Green Rust II- Iron Fe(OH)Fe(OH)3 3 // FeFe33(OH)(OH)88
Theophrastite – NickelTheophrastite – Nickel [Ni(OH)[Ni(OH)22]]
Annabergite – Nickel [NiAnnabergite – Nickel [Ni33(AsO(AsO44))22 • • 8H8H22O]O]
Basaluminite – Aluminum Basaluminite – Aluminum [Al[Al44SOSO4 4 (OH)(OH)10 10 • • nHnH22O]O]
Tailings Neutralization ProcessTailings Neutralization ProcessInitial ReactionInitial Reaction
Analyte (mg/L) (% prec.)
Al
As
Fe
Ni
Si
420
732
2,400
560
260
0.0
0.0
0.0
0.0
0.0
Solution pH 1.5
McClean Lake OperationMcClean Lake Operation
Tailings Neutralization ProcessTailings Neutralization ProcesspH GradientpH Gradient
Analyte (mg/L) (% prec.)
Al
As
Fe
Ni
Si
420
659
2,328
532
260
0.0
~10
~3
~5
0.0
Solution pH 1.5
McClean Lake OperationMcClean Lake Operation
Tailings Neutralization ProcessTailings Neutralization Process Bulk NeutralizationBulk Neutralization
Analyte (mg/L) (% prec.)
Al
As
Fe
Ni
Si
420
150
1,600
500
260
0.0
79.5
33.3
10.7
0.0
Solution pH 2.2
McClean Lake OperationMcClean Lake Operation
Tailings Neutralization ProcessTailings Neutralization ProcessBulk NeutralizationBulk Neutralization
Analyte (mg/L) (% prec.)
Al
As
Fe
Ni
Si
290
0.5
570
450
140
31.0
99.9
76.3
19.6
46.2
Solution pH 4.0
McClean Lake OperationMcClean Lake Operation
Tailings Neutralization ProcessTailings Neutralization Process Bulk NeutralizationBulk Neutralization
Analyte (mg/L) (% prec.)
Al
As
Fe
Ni
Si
0.5
0.08
340
250
17
99.9
100.0
85.8
55.4
93.5
Solution pH 6.1
McClean Lake OperationMcClean Lake Operation
Tailings Neutralization ProcessTailings Neutralization Process Bulk NeutralizationBulk Neutralization
Analyte (mg/L) (% prec.)
Al
As
Fe
Ni
Si
0.5
0.06
2.2
1.3
3.2
99.9
100.0
99.9
99.8
98.8
Solution pH 7.4
McClean Lake OperationMcClean Lake Operation
Tailings Neutralization ProcessTailings Neutralization ProcessAgingAging
Analyte (mg/L) (% prec.)
Al
As
Fe
Ni
Si
0.5
0.06
2.2
1.3
3.2
99.9
100.0
99.9
99.8
98.8
Solution pH 7.4
McClean Lake OperationMcClean Lake Operation
Flow DiagramFlow Diagram
RAFFINATEpH = 1.5pe = 11.88As = 747 mg/LNi = 571 mg/LFe = 2,450 mg/L
EQUILIBRATEpH = 7
Ni3(AsO4)2 • 8H2OFERRIHYDRITE
SOLUTION 11pH = 7As = 291 mg/LNi = 35.8 mg/LFe = 554 mg/L
MIXRAFFINATE
SOLUTION 11
MODEL SOLUTION 6-1pH = 2.18pe = 11.7As = 64.7 mg/LNi = 518 mg/LFe = 1,830 mg/L
EQUILIBRATEpH = 2.18
SCORODITEGYPSUM
90% 10%
Comparison Data and ModelComparison Data and Model
0.10
1.00
10.00
100.00
1,000.00
10,000.00
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
pH
Co
nc
en
tra
tio
n (
mg
/L)
As Model As Fe Model Fe Ni Model Ni
Fe
Ni
As
Comparison Data and ModelComparison Data and Model
0.01
0.10
1.00
10.00
100.00
1,000.00
10,000.00
100,000.00
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
pH
Co
ncen
tratio
n (m
g/L
)
As Model As Fe Model Fe Al Model Al Sulfate Model Sulfate Ni Model Ni
Sulfate
Fe
Al
Ni
As
ConclusionsConclusions
Scorodite is dominant As - bearing phaseScorodite is dominant As - bearing phase Balance between relatively stable scorodite and less Balance between relatively stable scorodite and less
stable ferrihydritestable ferrihydrite Adjustments to Ksp produce best fitAdjustments to Ksp produce best fit Precipitation stops by pH ~ 5Precipitation stops by pH ~ 5
As concentrations < 1 mg/LAs concentrations < 1 mg/L Little or no evidence of As sorption processLittle or no evidence of As sorption process Disequilibrium removes some nickelDisequilibrium removes some nickel
Nickel mainly in theophrastiteNickel mainly in theophrastite Model concentrations higher than measuredModel concentrations higher than measured Sorption may also play a roleSorption may also play a role
