reactivity of various zero valent irons: reduction of trichloroethylene saving the world! lauren...
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Reactivity of Various Zero Valent Irons: Reduction of Trichloroethylene
Saving the World!
Lauren Vice, Jim Nurmi, John Schneider, Paul TratnyekDepartment of Environmental and Biomolecular Systems
OGI School of Science and EngineeringOregon Health & Science University
ARS Technologieshttp://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
• Determine rate of TCE disappearance (kobs) with various ARS irons, and
• Measure presence and rate of appearance of daughter products.
Proposed pathway
HC
C
Cl
Cl
Cl
HC
HC
Cl
Cl
HC
CH2
Cl
H2C
CH2
H3C
CH3
HC
C
Cl
TCE
DCE
VC
ethene
Ethylene chloride
ethane
Batch Experiments
• HP 5890 Gas Chromatographer with DB 624 Column
TCE Degradation
Initial TCE spike, .0523 M
60x10-3
50
40
30
20
10
0
[TCE], M
9000800070006000500040003000200010000
Time, min
TCE Degradation with ARS Iron Samples
'Sponge (A) 5g' 'Cast (B) 5g' 'Ultra-Fine (C) 5g' 'HSA (D) 20g' 'QMP (E) 20g' 'Control'
wave0
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 High-Sulfur Atomized Iron
• Study of pH effects on degradation
• Look at longevity of various irons degradation abilities with chlorinated solvents
Thanks