Edwards - Bioleaching of Nickel-Containing Wastes – OGI Life Sciences and Mining Workshop 2014

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/[email protected]?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&currency=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