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Nanoparticles NZVI and TCE Need Statement, Objectives, and Hypotheses Prior Work Research Phase I : TCE Degradation with NZVI Research Phase II : TCE degradation with Pseudomonas and
NZVI Research Phase III : TCE degradation with Dehalococcoides
and NZVI Conclusions and Future Work Acknowledgements
2
Nanoparticles (NPs)5
(NPs) < 100 nm
NPs : Colloidal particles, Reactive species
NPs Classification
Metallic (gold, iron, nickel, cobalt)
Semiconductor (quantum dots)
Polymeric (poly (L-lactic acid or PLA))
Others (Clay NPs)
ASTM International, 2006; Liu et al., 2006
Applications of Nanoparticles
Natural processes: Ubiquitous
Cosmetics: TiO2, ZnO
Hand Sanitizers: Ag NPs
Lipsticks as pigments: Iron oxide NPs
Dental fillers, prosthetic implants, drug carriers: SiO2 NPs
Environmental applications
6
NPs for Environmental Remediation
Water quality improvements
Treatment - contaminated soils, sediments and solid wastes
Halogenated/ Polychlorinated hydrocarbons, certain pesticides
(DDT, lindane)
Hydrocarbons, dyes, and other inorganic anions such as nitrate,
perchlorate, dichromate, and arsenate
US EPA, 2007; Thompson et al., 2010; Zhang, 2003
7
Nanoparticles Contaminant ReferenceNano Zeolites Toluene, nitrogen dioxide Song et al. (2004)
Carbon nanotubes (CNTs) p-nitrophenol, benzene, toluene, heavy metal ions,dimethylbenzene
Jin et al. (2007)
Bimetallic nanoparticles (Pd/Fe)
PCBs, chlorinated methane, ethene, Trichloroethylene (TCE)
Xu and Bhattacharyya (2005)Xu and Zhao (2007)Wang and Zhang (1997)Kim et al. (2010)
Ni/Fe and Pd/Au nanoparticles
TCE and PCBs He and Zhao (2005)
TiO2 photocatalyst Heavy metal ionsPentachlorophenol (PCP)
Pena et al. (2005)Quan et al. (2005)
NZVI Herbicides (Alachlor) Thompson et al. (2010)
NZVI Nitrate Bezbaruah et al. (2009)
NZVI TCE Bezbaruah et al. (2011)
NPs for Water Remediation8
Why NZVI?
Non-toxic and inexpensive
Feº is a potential reducing agent
Reactive species
High surface area
Can reductively degrade contaminants
Image Credit: Matheson, and Tratnyek, 1994
Fe0 Fe 2+ + 2e-
R-X + 2e- + H+ R-H + X-
Bezbaruah et al. 2009; Thompson 2010; Zhang 2003
9
Contaminant
Trichloroethylene (TCE)
Solvent / Degreasing agent
WHY TCE?
Ranked as one of the most hazardous compounds (worst 10%)
Most commonly detected volatile organic in groundwater
Suspect carcinogen /Endocrine toxicant/Kidney toxicant
EPA permissible levels: 5 ppb
10
U.S. EPA, 2011
TCE Contaminated Sites
61% NPL sites contaminated with TCE
Valley City, ND
Baytown township groundwater contamination site (Minnesota) – monitored by MPCA
Hibbing, Minnesota
11
USEPA 2007
Challenges
High mobility causes NZVI to sediment out in the aquifer pores and become unavailable for contaminant remediation
Existing technology for TCE removal is not efficient enough
14
More on TCE Remediation Methods15
Physical Methods: Expensive/Maintenance
Chemical Methods: By-product generation, short life span
Bioremediation: Slow/ Time consuming
There is a need to develop a more efficient method
Objectives
To engineer a metal-microorganism system for TCE remediation
Specific Objectives
Encapsulation of NZVI (in Ca-alginate capsules)
TCE remediation with encapsulated NZVI
Encapsulation of TCE degrading bacteria
TCE remediation with encapsulated bacteria
TCE remediation with NZVI-microorganism system
Quantify the reaction kinetics of TCE degradation
16
Hypotheses17
NZVI can reduce TCE as the first step in the degradation process and then the microorganisms can preferentially take over the process
NZVI-microorganism system will effectively dechlorinate TCE to benign end products
TCE Degradation Mechanism - NZVI
C=C Cl
Cl H
Cl
Fe0
Cl-
e-
C=C H
Cl H
ClFe0
Cl-
e-
C=C H
Cl H
H
Fe0
Cl-
e-
C=C H
H H
H
TCE DCE
VC
Ethene
18
Model Microorganisms
Pseudomonas putida F1 strain
Capable of oxidizing organic contaminants
Dehalococcoides sp.
Reductive dechlorination
Converts TCE benign products (ethene)
Some strains convert TCE VC
D. BAV1 : TCE Ethene
19
www.miller-mccune.com
http://gtresearchnews.gatech.edu/
Experimental Design24
Microorganisms
Pp F1D.
BAV1
Encapsulated Microorganisms
Combined NZVI-Microorganism System
TCE Degradation
NZVI
Bare Encapsulated
Encapsulated NZVI
Research Phase I
Research Phase I
Synthesis of NZVI
Preparation of Ca-alginate Capsules (Reactors)
Encapsulation of NZVI
Batch Experiments:
Diffusion Studies
TCE Degradation Studies
Summary
26
Synthesis of NZVI
NZVI-synthesized by borohydroxide reduction method 2Fe2+ + BH4
- + 3H2O 2Fe0↓ + H2BO3- + 4H+ + 2H2
TEM image of clustered nanoparticles
Krajangpan et al. 2009; Bezbaruah et al. 2009; Bezbaruah et al. 2011
a
b
a and b: Dried NZVI
XRD spectrum of NZVI
27
Encapsulation
“Encapsulation” confining compounds within a matrix or
membrane in particulate form
Encapsulated particles/compounds are free to move
“Entrapment” embedding of compounds within a matrix
Entrapped particles/compounds are not free to move
Mobility and settlement problems can be overcome using
NZVI
(Bezbaruah et al., 2009; Bezbaruah et al., 2011)
28
Why alginate?
Bio-degradable
Non-toxic
Porous
Inexpensive
Used in bacterial cell immobilization
29
Hill and Khan, 2008
Preparation of Capsules
4 g Maltodextrin6 mL DI water
0.25 g CaCl2
50 mL alginate
Peristaltic pump
Stirrer
6 cm b
a: Capsules
30 mg NZVI
1.33% Iron loss
a
30
Bezbaruah et al., 2011
b
b: Encapsulated NZVI
Batch Experiments
DIFFUSION STUDIES
Empty alginate capsules used
45 mL reactors containing 30 and 40 mg TCE /L
Shaken in a rotary shaker
Samples (40 µL) collected over specific time intervals
Experiments done in triplicates
31
Capsules
TCE Solution
40 mL Vial
Diffusion Study Results
Bulk TCE concentration decreased and then began to level off ~45 min
Establishes that: NO major mass transfer barrier for contaminant diffusion through Ca-alginate capsules
32
TCE Degradation Batch Studies33
Encapsulated NZVI
Samples collected over time
2 h (Rotated)Blank Control Analysis
Capsules
TCE Solution
TCE Solution
TCE Solution+ Bare NZVI
TCE Degradation Batch Study
TCE removal efficiency of 88-90% using bare NZVI
TCE removal efficiency of 89-91% using encapsulated NZVI
Bare and encapsulated systems performed almost the same
34
TCE Degradation Kinetics
TCE degradation followed First Order Kinetics for both bare and encapsulated NZVI
No significant difference Bare and Encapsulated NZVI (95% CI, Two Way ANOVA )
35
Batch Initial TCE concentration
mg L-1
Reaction rate constant R2
k obs
10-2 min-1
ksa
10-3 L m-2 min-1
Bare NZVI 1 2.92 1.6 0.968910 2.35 1.3 0.980130 1.53 0.8 0.989740 2.24 1.2 0.9868
Encapsulated NZVI
1 3.23 1.7 0.983210 2.45 1.3 0.949130 1.92 1.0 0.992140 2.21 1.2 0.9425
Bezbaruah et al., 2011
Encapsulated NZVI: pH Observations
pH changed from 6 to 9 as the reaction proceeded
Similar results irrespective of concentration
No NZVI – No pH change
36
Research Phase I-Summary
Encapsulated NZVI degraded 89-91% of TCE
Shelf-life of 4 months
TCE removal with NZVI followed First Order Kinetics
Potential scope for groundwater applications
38
Work Remaining39
Microorganisms
PpF1D.
BAV1
Encapsulated Microorganisms
Combined NZVI-Microorganism system
TCE Degradation
NZVI
Bare Encapsulated
Encapsulated NZVI
Experimental Design40
Microorganisms
PpF1D.
BAV1
Encapsulated Microorganisms
Combined NZVI-Microorganism system
TCE Degradation
NZVI
Bare Encapsulated
Encapsulated NZVI
Research Phase II
TCE Degrading Bacteria42
Microorganism Method of Removal End Product Reference
Pseudomonas putida F1 Direct OxidationCo-metabolism
ETH (Sun and Wood 1996); (Kim et al. 2010b); (Radway et al. 1998)
Clostridium bifermentans DPH-120 Co-metabolism c-DCE (Chang et al. 2000)
Dehalospirillum multivorans Direct Oxidation c-DCE (Neuman et al.1994)
Dehalococcoides ethenogenes 195 Reductive dechlorination
ETH (Maymo-Gatell et al. 1999), (Fennell et al. 2001)
Dehalococcoides BAV1 Reductive dechlorination ETH (Krajmalnik-Brown et al. 2004; Maymo-Gatell et al. 1999),(He et al. 2003)
Dehalococcoides VS Reductive dechlorination ETH (Cupples et al. 2003)
Dehalococcoides FL2 Reductive dechlorination ETH (El Fantroussi et al. 1998)
Model Microorganisms
Pseudomonas putida F1 strain
Capable of oxidizing organic contaminants
Dehalococcoides sp.
Reductive dechlorination
Converts TCE benign products (ethene)
Some strains convert TCE VC
D. BAV1 : TCE Ethene
43
www.miller-mccune.com
http://gtresearchnews.gatech.edu/
Research Phase II
Growth Study
Encapsulated Pp F1 for TCE degradation
Encapsulated NZVI for TCE degradation in media
Combined NZVI- Pp F1 system
TCE re-dosing Experiment
Summary
45
Pseudomonas putida F1 strain
Culture: obtained from ATCC
Optimal growth temperature: 300C
46
www.miller-mccune.com
Growth Curve- Pseudomonas putida F1
P. putida incubated at 30oC in TSB media and shaken for 24 h
1 mL aliquot (0-24 h )
Serial dilution and nutrient agar plating
Incubated for 24 h at 30oC
Plate count and plotting of Viable Cells/mL vs Time
47
Growth Curve
Bacteria harvested at 12 h for TCE degradation study
48
Viable cell count = Number of colonies * (1/Dilution) * (1/Volume)
Pseudomonas putida F1 for TCE Degradation
1mL of overnight culture (12 h) encapsulated
Encapsulated Pp F1added to TCE in TSB media (10 mg/L)
Reactors shaken end-over end
Aliquots withdrawn at regular intervals
50
NZVI in Growth Media
Purpose: To check whether NZVI behaves differently in media
Protocol:
0.75g/L NZVI +25 mL TCE solution amber vial (10mg/L TCE)
Rotated end-over-end at 28 rpm
Samples collected over time
Result: NZVI degrades TCE in media
52
Blank NZVI + TCE (in media)
Batch Experiments53
Purpose: Metal-microorganism system for TCE removal
Batch Study Protocol:
Encapsulated NZVI -P. putida F1+TCE (in media)
Rotated – 3h
TCE analysis
Encapsulated NZVI
Encapsulated P.putida F1
TCE Solution
40 mL Vial
Re-dosing Experiments
Purpose: To understand the individual roles of NZVI and Pp F1
Rotated End-over-end for 3h
Remove TCE solution
Add new TCE solution
Rotated End-over-end 36 h
Aliquots
Analysis
54
Results
TCE degradation 0-3h (NZVI dominated)
TCE degradation 3-36h (Bacteria dominated)
Add new TCE Solution
55
Kinetic Studies57
E-NZVI: Encapsulated NZVI, E-B: Encapsulated Bacteria, C-NZVI: Combined System (NZVI dominated), C-B: Combined system (bacteria dominated)
Reaction order E-NZVI E-B C-NZVI C-B
Zero
Kobs
mg·L-1·min-1 5.92 2.0 6.05 3.5
R2 0.8764 0.57 0.90 0.84
1st
Kobs
min-1 2.33 4.0 2.47 5.0
R2 0.980 0.66 0.96 0.90
2nd Kobs
L·mg-1·min-1 2.31 8.0 2.80 9.0
R2 0.778 0.74 0.78 0.93
Research Phase II- Summary
Metal-Microorganism system was successfully designed
Pp F1 and NZVI were encapsulated separately
TCE was completely removed after 3 h (~ 100%) (NZVI dominated) and ~70% (bacteria dominated) in 36 h after re-dosing
58
Work Remaining59
TCE Degradation
NZVI
Bare Encapsulated
Encapsulated NZVI
Microorganisms
PpF1D.
BAV1
Encapsulated Microorganisms
Combined NZVI-microorganism system
Research Phase III
Research Phase III
Growth Study
Encapsulated DBAV1for TCE degradation
Encapsulated NZVI for TCE degradation in media
Combined NZVI- DBAV1system
TCE re-dosing Experiment
Summary
61
Dehalococcoides BAV162
Anaerobic bacteria
Method: Reductive dechlorination
Capable of reducing TCE ethane
Culture obtained from ATCC
D.BAV1 growth Studies63
D.BAV1 incubated at 22±2 o C in (MSM) media and shaken
1 mL aliquot at regular interval (0-36 h )
Serial dilution and nutrient agar plating
Incubated for 24 h at 22±2 oC
Plate count and plotting of Viable Cells/mL vs Time
TCE Degradation Batch Studies65
Combined metal-microorganismEncapsulated D.BAV1
Encapsulated NZVI (re-dosed)Encapsulated NZVI
pH-ORP Change
ORP- Reducing conditions
Increase at 3 h – exposure to air
pH- initial increase (reaction with NZVI)
Constant throughout the reaction
67
Kinetic Study68
Reaction order E-NZVI E-B C-NZVI C-B
Zero Kobs
(mg·L-1·min-1)
5.83 6.6 6.01 5.00
R2 0.863 0.33 0.89 0.82
1st
Kobs
(min-1)
2.76 4.90 2.93 3.80
R2 0.912 0.92 0.93 0.86
2nd
Kobs
(L·mg-1·min-1)
8.35 2.85 1.08 6.05
R2 0.636 0.63 0.64 0.41
Research Phase III -Summary
D BAV1and NZVI were co-encapsulated
TCE was completely removed after 3 h (~ 100%)
(NZVI dominated)
After re-dosing TCE removal ~ 100%
(Bacteria dominated)
First order kinetics
69
Conclusions
Encapsulation of NZVI in alginate polymer : viable for TCE
dechlorination
Encapsulation of microorganisms in alginate polymer :
efficient technique for TCE removal
DCE and VC: not detected
Combined metal-microorganism was successful with the
advantages of both NZVI and microorganisms
Potential for in-situ remediation applications (e.g., PRBs)
70
Future Directions
Interferences of other groundwater contaminants (electrons acceptors like nitrate and dissolved oxygen)
Shelf-life of the combined NZVI-microorganism system
The roles of NZVI and bacteria in a combined system
Make it versatile (Other Contaminants)
71
Acknowledgements
ND Water Resource Research Institute
Department of Civil Engineering
Dr. Achintya Bezbaruah
Dr. Eakalak Khan
Dr. Senay Simsek
Dr. G. Padmanabhan
NRG Group
Members of the Environmental Engineering Laboratory
72