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