Reactivity of Various Zero Valent Irons:
Reduction of Trichloroethylene
Saving the World!
Lauren Vice, Jim Nurmi, John Schneider, Paul Tratnyek
Department of Environmental and Biomolecular Systems
OGI School of Science and Engineering
Oregon Health & Science University
ARS Technologies
http://www.arstechnologies.com
Chlorinated Solvents and Possible Remediation
•
Chlorinated Solvents are widely used
and manufactured
– 1980 = 121,000 metric tons of TCE
produced
•
Suspected carcinogens & harmful to
aquatic organisms
•
Natural Remediation
•
Permeable Reactive Barriers (PRB’s)
– Reduce chlorinated solvents
1.
1Blowes, David (2007, May). In Situ. Retrieved August 15, 2008, from In Situ Treatment of Metals and other Inorganic Contaminants in Groundwater
using Permeable Reactive Barriers: Treatability Testing Web site: http://www.science.uwaterloo.ca/research/ggr/EC_AerialView.jpg
Primary Objective
Proposed pathway
•
•
Determine rate of TCE
disappearance (kobs) with
various ARS irons, and
Cl
TCE
Measure presence and
rate of appearance of
daughter products.
C
HC
Cl
Ethylene
chloride
Cl
H
C
DCE
Cl
HC
Cl
C
HC
Cl
CH2
VC
HC
Cl
CH2
ethene
H2C
ethane
H3C
CH3
Batch Experiments
•
HP 5890 Gas Chromatographer with DB 624 Column
TCE Degradation
60x10
-3
TCE Degradation with ARS Iron Samples
50
[TCE], M
40
30
'Sponge (A) 5g'
'Cast (B) 5g'
'Ultra-Fine (C) 5g'
'HSA (D) 20g'
'QMP (E) 20g'
'Control'
20
10
wave0
0
0
1000
2000
3000
4000
5000
6000
7000
8000
Time, min
Initial TCE spike, .0523 M
9000
Various Rate Constants
Iron
kObs
(min-1)
kMass
(min-1 g-1)
kSA
(L m-2 min-1)
Sponge
(5g)
1.367E-04
2.734E-05
1.20E-04
Cast
(5g)
2.044E-04
4.088E-05
4.78E-05
Ultra-Fine
(5g)
7.0931E-05
1.419E-05
1.18E-05
HSA
(20g)
2.536E-04
1.268E-05
7.54E-06
QMP
(20g)
2.0267E-04
1.013E-05
3.95E-05
Comparing Various Rate Constants for both CT and TCE
Carbon Tetrachloride
Trichloroethylene
Conclusion
•
With out major research on daughter products of all five
ARS iron types no clear conclusion can be made on which
of the five irons is most efficient at degrading chlorinated
solvents
•
Further data must be collected
Suggestions for Future Research
•
Further study of product peaks, such as those seen with HighSulfur Atomized Iron
•
Study of pH effects on degradation
•
Look at longevity of various irons degradation abilities with
chlorinated solvents
Thanks