<8TH Annual Meeting of DWRIP 2014, January 30>
Hybrid composites of nano-sized zero
valent iron and covalent organic polymers
for groundwater contaminant degradation
Paul Mines1,2, Jeehye Byun2, Y. Hwang1, H. Patel2, H. Andersen1, C. Yavuz2
1
2
Department of Environmental Engineering, DTU, Denmark
Graduate School of Energy, Environment, Water and Sustainability, KAIST, Korea
Introduction – Nano-sized Zero Valent Iron
(nZVI)
Extremely effective at degrading
a wide variety of contaminants in
water sources
• Chlorinated organics, azo dyes,
pesticides, inorganic ions
• Compounds are often not
amenable to biodegradation
Ref: Daniel Cha, U. of Delaware
Reaction scheme for nZVI with chlorinated organics:
0
2+ + 2𝑒 −
• 𝐹𝑒 → 𝐹𝑒
TCE
+
−
• 2𝐻2 𝑂 → 2𝐻 + 2𝑂𝐻
+
−
• 2𝐻 + 2𝑒 → 𝐻2 ↑
+
−
−
• 𝑥 ∙ Cl + 𝐻 + 2𝑒 → 𝑥 ∙ 𝐻 + 𝐶𝑙
+
−
−
• 𝐶2 𝐻𝐶𝑙3 + 3𝐻 + 6𝑒 → 𝐶2 𝐻4 + 3𝐶𝑙
acetylene
ethene
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ethane
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Introduction – nZVI Stabilization
Conventional technology – permeable reactive barriers (PRBs)
• Limited by stability of ZVI in groundwater
•
Fe0 aggregates together, forms large particles, settles out, becomes inactive
Widespread application requires that nZVI remains stable and maintains its
reactivity
• Applicable for in situ PRBs or ex situ pump-n-treat operations
PRB
Ref: EnviroMetal, Inc.
Ref: PNF Nano-Engineering & Manufacturing Co.
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Introduction – Covalent Organic Polymers
(COPs)
•
Hybrid materials improving on conventional covalent organic
framework (COF) technology at lower cost.
•
•
Offer extremely high surface areas
•
•
No post-processing or cross-linking necessary
Up to 600 m2/g
Proven adsorbent for CO2 capture applications
•
Up to 5600 mg-CO2/g-COP (@200bar/318K)
(Patel et al., 2012)
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Annual meeting of DWRIP
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COP Chemistry
Polymer
Core Molecule
Linker Molecule
Solubility
COP1
Triazine trichloride
Piperazine
Miscible in water
Solvent used:
H2 O
COP6
Triazine trichloride
4,4’-thiobisbenzenethiol
Immiscible in water
Solvent used:
N,N-Dimethylformamide
(DMF)
COP19
Terephthaldehyde
Melamine
Miscible in water
Solvent used:
H2 O
COP60/61
Benzene tricarbonyl trichloride
Not yet published
---
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Immiscible in water
Solvent used:
N,N-Dimethylformamide
(DMF)
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Overall Objectives
•
Stabilization
•
•
Remediation of azo dyes
•
•
•
Poses significant environmental risk due to toxicity and widespread
global application
Acts as model pollutant for degradation of other recalcitrant chemicals
Prove a synergistic effect of the composite material
•
•
Prove feasibility of COP materials as effective supporting and
stabilizing agents for nZVI
Show effective decolorization of azo dye with COPs
• Combining adsorption from COP material and degradation from
impregnated nZVI
Eventual target  halogenated organics (TCE, PCE, etc.)
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Materials and Methods
1. Synthesis of nZVI impregnated COPs
FeCl3
- quantity in 20mL
COP
- quantity in 20mL
NaBH4
0.05 mol/L
0.162g
2% (w/v)
0.400g
0.15 mol/L
- quantity in 20mL
0.114g
Impregnation Time
24 hours
Solution Filtration
Reduction Time
Vacuum Drying Time
@ 120°C
Yes
30 minutes
12 hours
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Materials and Methods
2. Characterization




Transmission electron microscopy (TEM)
Inductively coupled plasma – mass spectrometry (ICP-MS)
 Total iron content within composites
X-ray diffraction (XRD)
 Confirmation of presence of Fe0
BET surface area
3. Stabilization Test

Optical absorbance at 508nm using UV-Vis spectrometer (Phenrat et
al., 2007)
4. Reactivity Test

Azo-dye decolorization
- Acid Black I (60µM) / HEPES buffered (10mM)
- Reaction solution: 1.5g composite/L dye solution
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TEM Imaging
COP6/nZVI
COP19/nZVI
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Iron Contained in Composites (ICP-MS)
1.0
mg-Fe/mg-composite
0.8
0.6
0.4
0.2
0.0
nZVI
COP1
COP6
COP19
COP60
COP61
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Presence of Fe0 (XRD)
COP19/nZVI
400
400
350
350
300
300
250
250
200
0
Fe @ 44.9°
150
Intensity
Intensity
Pure nZVI
200
150
0
Fe @ 44.9°
100
100
50
50
0
0
5
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
2 (deg)
5
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
2 (deg)
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Composite BET Surface Area Analysis
600
600
Bare Polymer
Composite (COP + nZVI)
2
Surface Area (m /g)
500
400
332.4
300
200
100
168
72.1
37
17.3
9.1
8.9
8.8
0
COP1
COP6
COP19
COP60
5.9
COP61
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Composite Stability Testing
Sedimentation Test
• Optical absorbance @ 508nm
1.0
0.8
A/Ao
0.6
0.4
nZVI
COP1
COP6
COP19
COP60
COP61
0.2
0.0
0
5
10
15
20
25
30
35
40
45
50
55
60
Time (minutes)
COP/nZVI composites show increased stability vs. pure nZVI
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Acid Black I Decolorization Images
Alias: Naphthol blue black
Molecular Formula: C22H14N6Na2O9S2
Molecular Weight: 616.499 g/mol
Peak Absorbance (λmax): 618nm
t=0
COP1/nZVI
t=30 D.I.
1,2,7-triamino8-hydroxynaphthalene3,6-disulfonate
t=0
COP19/nZVI
t=30 D.I.
+
aniline
t=0
COP60/nZVI
t=30 D.I.
+
p-nitro-aniline
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p-phenylene-diamine
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Dye Decolorization UV-Vis Spectra
COP1
Absorbance
3
2
COP1/nZVI
• Combination of dye adsorption and
degradation
COP19/nZVI
• Primarily dye adsorption
COP60/nZVI
• Little to no adsorption or degradation
Initial
1
2.5
5
7.5
10
15
20
30
1
0
300 330 360 390 420 450 480 510 540 570 600 630 660 690 720 750 780
Wavelength (nm)
COP19
2
3
Initial
1
2.5
5
7.5
10
15
20
30
Absorbance
Absorbance
3
COP60
1
2
Initial
1
2.5
5
7.5
10
15
20
30
1
0
0
300 330 360 390 420 450 480 510 540 570 600 630 660 690 720 750 780
Wavelength (nm)
300 330 360 390 420 450 480 510 540 570 600 630 660 690 720 750 780
Wavelength (nm)
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Acid Black I - Peak Absorbance vs. Time
1.0
0.8
C/C0
0.6
COP1
COP6
COP19
COP60
COP61
Act. C
0.4
0.2
0.0
0
5
10
15
20
25
30
Reaction Time (minutes)
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COP6: Polymer vs. Composite Decolorization
1.0
0.8
C/C0
0.6
Bare Polymer
Composite (COP6 + nZVI)
0.4
0.2
0.0
0
5
10
15
20
25
30
Reaction Time (minutes)
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Surface Area vs. Decolorization
Water Miscible Water Immiscible
350
1.0
300
0.8
1 - (C/C )
0
250
2
0.6
200
150
0.4
1 - (C/C0)
Surface Area (m /g)
Surface Area
100
0.2
50
0
0.0
COP1
COP19
COP6
COP60
COP61
nZVI/Polymer Composite
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Conclusions
nZVI/COP Synthesis
• Successfully impregnated nZVI within the COP matrices (~10%)
Effective Stabilization of nZVI
•
Loading nZVI into the COP matrix proves much more stable than bare nZVI
Successful Azo Dye Decolorization
•
Depending on the COP, achieved decolorization in the form of adsorption,
degradation, or a combination of both
Wettability of the Polymer
•
•
Decolorization is highly dependent on the wettability of the COP material
Migration of the azo dye in the aqueous phase must be possible and depends on the
nature of the composite material
Surface Area of the Composite Material
•
Decolorization is also dependent on the total surface area of the nZVI/COP material
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Thank you for attention
Any questions & comments?
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