Edwards - Bioleaching of Nickel-Containing Wastes – OGI Life Sciences and Mining Workshop 2014
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Bioleaching of Nickel-Containing Wastes
Department of Chemical Engineering and Applied Chemistry - University of Toronto
Elizabeth A. Edwards
Wendy Han Zhou, Srinath Garth, Cheryl Devine Vladimiros Papangelakis Krishna Mahadevan
Outline
• Acid Mine Drainage and Microbial Metabolism • Can we recover nickel from hazardous wastes? • Challenges for bioleaching • Neutral bioleaching of ultramafic concentrates • Acidic bioleaching of pyrrho@te • Perspec@ves moving forward
Problem of Acid Mine Drainage
3
Nickel Bioleaching Poten:al • Biologically-‐enhanced acid mine drainage known to occur
• Bioleaching of minerals presently used for other low-‐grade ores and concentrates
hEp://www.azom.com/ar@cle.aspx?Ar@cleID=1601
Commercial Ni Bioleaching Process
Talvivaara’s Sotkamo mine heap-‐leach (Finland): • The mine produced 12,000 t of Ni (along with Zn, Cu, Co, and U)
from Ni grade of 0.23% via heap bioleaching • The presence of pyrite enhances leaching
Poten:al Low-‐Grade Ni Resources 1. Pyrrho@te-‐rich tailings from nickel mills (Sudbury)
2. Ultramafic ores: low-‐grade, Mg-‐rich concentrate (MB)
6 1A. R. Barnes et. al, “Pyrrho@te tailings: Waste or resource?,” in MEI Conference Nickel Processing, Falmouth, 2010. 2hEp://www.indexmundi.com/commodi@es/?commodity=nickel&months=60¤cy=cad)
Pyrrho@te “reserve” in Sudbury
100 Mt1 (~0.8% Ni)
Ultramafic ore reserve (MB) >425 Mt (0.5-‐0.7% Ni)
Nickel available 800,000 tonnes
2.1-‐2.9 Mt
Nickel value (at 80% recovery, $14,000/tonne Ni) 2
$9 billion >$25-‐32 billion
Can this nickel be recovered quickly, economically, and with minimal environmental impact?
Bioleaching Mechanism Acid produc@on
Poten@ally valuable byproduct
Overview of Microbial Metabolism
Enzymes in a microbe"
Electron Donor or Substrate (Reduced)"
Sugars, Proteins, Fats"
Electron Donor or Substrate (Oxidized)"
CO2 "
Electron Acceptor (Oxidized)"
Oxygen (O2)"
Electron Acceptor (Reduced)"
Water "
Nitrate (NO3)""Sulfate (SO4)
Fe(III), CO2"
N2, H2S"Fe(II), CH4"
Toluene, benzene"
Something to eat Something to “breathe”
H2O, Fe(III), So, SO42-"
H2, Fe(II), H2S, FeS
If energy is released (DeltaG<0) then microbe can grow
Redox Considera:ons: Fe Oxida:on
Hedrich, S., et al., (2011) Microbiology 157: 1551-‐1564
The Electron Tower – Microbiologist’s perspective Electrons flow down the tower….
(1)
(2)
(3)
Redox couple E0ʹ′ (V) -0.60
+0.10
-0.50
-0.40
-0.30
-0.20
-0.10
+0.20
+0.30
+0.40
+0.50
+0.60
+0.70
+0.80
+0.90
0.0
(1) H2 + fumarate2- succinate2-
(2) H2 + NO3- NO2
- + H2O
(3) H2 + O2 H2O 12
∆G0 ʹ′ = –163 kJ
∆G0 ʹ′ = –237 kJ
∆G0 ʹ′ = –86 kJ
Electron Donor and Electron Acceptor half reactions Energy is released if you oxidize a redox couple higher in the tower, and electrons are accepted by a redox couple lower in the tower
Sulfur and Iron oxidizing bacteria widely distributed in nature
Bioleaching Challenges • Mineral dissolu@on and reac@vity a complex func@on of pH, temperature, redox, oxygen, microbes, chelators and ore composi@on…
• Low pH, high temperatures enhances rates, but may dissolve too many other things…
• Neutral pH, though slower, might provide higher selec@vity of Ni over Mg and end up with a more benign solu@on at the end – What is op@mum pH?
• Could we use nitrate instead of oxygen? More soluble, less acid genera@on?
• Can we stop the oxida@on at elemental So?
Poten:al for Acid Genera:on
The cell as a ba]ery: Proton Mo:ve Force
Electron donor
Electron Transport Chain
Electron acceptor
INSIDE
OUTSIDE
Most microbes grow over a range of about 3 pH units, with clear op:mum
Two Ni Bioleaching Projects
• Took a microbial enrichment approach • Project #1: Ultramafic Concentrate (Mg) – Neutral bioleaching with O2 or Nitrate
• Project #2: Pyrrho@te – Acidic bioleaching at high solids concentra@on
• Microbial characteriza@on using next genera@on sequencing
Sulfide oxida@on coupled to nitrate reduc@on
Fe2+-‐>Fe3+ oxida@on coupled to nitrate reduc@on
Fe2+
Fe3+ NO3-‐
N2
Thiobacillus denitrificans
SO42-‐
S2-‐
T.E. Letain, S.I. Mar@n, H.R. Beller
• Faculta@ve anaerobe
• Couples the oxida@on of inorganic sulfur compounds to the reduc@on of oxidized nitrogen compounds (nitrate, nitrite) to N2 gas
• Op:mum condi:ons: pH 6.85 at 32.8 °C
20
Project #1: UMFC Bioleaching with a defined strain – Thiobacillus denitrificans
Ni5Fe4S8 + 13.6NO3-‐ + 5.6H+ + 3.2H2Oà 6.8N2(g) + 4Fe(OH)3(s) + 8SO4
2-‐
75% Indigenous sediment
25% Leaching medium
No e- Acceptor Control UMFC 5g
Maintain 0.5 - 5mM nitrate
Anaerobic Active UMFC 5g
Maintain 0.5 - 5mM nitrate
Sterile Control UMFC 5g
Maintain 0.5 - 5mM nitrate
Project #1: Microcosms Prepared Aug. 2012
Aerobic Active UMFC 5g
Purged with air every 2 weeks
• In serum boEles, at room temperature, pH 6.4 to 6.6.
• Analyzed for Ni and Mg dissolu@on, sulfate produc@on, and nitrate usage.
• Nitrate was replenished by adding KNO3 stock, to 5mM.
Analyzing Microbial Communi@es by Pyrotag Sequencing
Sample (Cells)
Extracted DNA
PCR Primers to Target Specific Sec@on of the Signature Gene (16S
rRNA Gene)
Amplifica@on Products from
PCR
Oil Droplets Containing Beads that Bind to PCR Products
1 PCR Product Piece Binding:
1 Bead: 1 Droplet
1 Hole on Pico@ter Plate Holds 1 Droplet
Automated Sequencing Yields
Thousands Reads per Sample
Sample sent to sequencing facility
22
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
WZexp7 WZexp8 WZexp9 0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
WZexp10 WZexp11 WZexp12
Aerobic vs. Denitrifying
23
Thiobacillus
Gallionellaceae
Chroma:ales
<1%
Aerobic condi@ons appear to encourage the growth of Thiobacillus, while anaerobic condi@ons seem to give a mix of Thiobacillus, Gallionellaceae, and ChromaHales. All are sulfur and iron oxidizing bacteria.
Thiobacillus
Aerobic Denitrifying
24
desulfobacterium anilini (EU020016.1) 1041
Polaromonas sp. strain JS666 (NR_074725.1) 4411 Pyrite mine AMD 16S clone (KC620646.1)
4252 Karst groundwater microbial community 16S clone (AM991243.1)
Dechloromonas agitata (NR_024884.1)
Nitrosomonadaceae 16S clone from gypsum-treated oil sands tailings pond (HQ043799.1) 594
2838
Zoogloea oryzae (NR_041286.1) Denitratisoma oestradiolicum (NR_043249.1)
6684 Limnobacter thiooxidans (NR_025421.1)
Rhodocyclaceae 16S clone from gypsum-treated oil sands tailings pond (HQ042342.1)
Castellaniella denitrificans (NR_044802.1) Accumulibacter phosphatis strain UW-1 (NR_074763.1)
5214 Iron-rich particles (Iron Snow) 16S clone (FR667826.1)
7494 Azospira oryzae (NR_024852.1) Dechlorosoma suillum (NR_074103.1)
Thiobacillus denitrificans (NR_074417.1)
408 Iron-reducing bacterium enrichment 16S clone (FJ802319.1)
3800
Thiobacillus sp. from gypsum-treated oil sands tailings pond (HQ086221.1) 3261
3487 Thiobacillus denitrificans (NR_025358.1)
6475 PAH degrading community 16S clone (FQ659310.1)
6263 Thiobacillus aquaesulis (NR_044793.1)
7062 Denitrification coupled to pyrite oxidation 16S clone (HM641565.1)
4471
343 Bioremediation by iron oxides and sulfides site 16S clone (JQ976370.1)
6467 Siderooxidans sp. (EU809885.1)
Sideroxydans lithotrophicus (NR_074731.1)
2280 Rhodocyclaceae 16S clone from CAHs contaminated groundwater (JQ279055.1)
56.2
21
100
15.1
6.9
9.1
2.8
100
67.1
22.6
2.3
50.2
100
75.1
17.3
6.7
21
78.8
61.1
100
77.6
100
28.6
98.9
99.4
99
79.9
17.8
73.8
85.1
99.2
17.3
99.8
61.2
56.7
93.2
38.4
92.5
90.7
99.7
97.1 90.2
0.03
Maximum Likelihood Phylogene@c Tree
S and Fe oxida@on coupled with denitrifica@on; Thiobacillus
S and Fe oxidizing; Found in Pyrite mine site, groundwater, and denitrifying environments.
Fe related environments; e.g. Iron Snow.
Project #1: Interim Summary • Obtained 3% Ni extrac@on under aerobic condi@ons, and 2% Ni extrac@on
under denitrifying condi@ons – but this is based on soluble Ni, not total Ni – Mass balance underway.
• Mg dissolu@on slowed while Ni dissolu@on increased with @me
• Sulfate was con@nuously produced and accounted for 86% of the stoichiometric amount of nitrate added
• Culture successfully transferred onto fresh UMFC and sulfate evolu@on con@nues – addi@onal Ni balances are underway
Enrichment cultures far outperformed pure culture on UMFC substrate
25
Project #2: Pyrrho:te Tails -‐ Low pH Sustained Ni Extrac:on and Bacterial Growth (pH=1.5)
Pyrotag Sequencing: Fe-‐oxidizing Acidophiles Are Abundant in Culture
• Supports proposed bioleaching ac@vity of culture • Highly enriched; specialized organisms • Enables easy tracking of organisms – qPCR, proteins
92%
1% 6%
92% Acidithiobacillus ferrooxidans Acidithiobacillus caldus Sulfobacillus thermosulfidooxidans
Summary
• Enrichment of Ni-‐leaching cultures successful on relevant solid substrates
• Near complete Ni extrac@on in acid bioleaching experiments
• Confirmed presence of specific organisms and their growth during leaching
Future Work
• Improving Ni mass balance in neutral bioleaching experiments
• Tracking growth of organisms via qPCR • Explore effect of chelators on rates of bioleaching • Enrich mixed cultures on single phases to select for e.g., pentlandite-‐oxidizing microbes
• Inves@gate methods for stopping sulfur oxida@on • Inves@ga@on into cheap fer@lizers for possible use in bioleaching
Acknowledgements
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