Title: Destruction of Organophosphorus Nerve Agent Analogues by Activation of O2 under Aqueous Room Tempera
1Destruction of Organophosphorus Nerve Agent
Analogues by Activation of O2 under Aqueous Room
Temperature and Atmospheric Pressure Conditions
- Christina Noradoun, Ryan Hutcheson, Edmund Wong,
I. Francis Cheng - University of Idaho, Department of Chemistry,
Moscow, ID 83844-2343 - ifcheng_at_uidaho.edu 208-885-6387
2Overall Goal
- The destruction or neutralization of xenobiotics.
- Inexpensive Safe Processes.
-
- Room Temperature and Pressure Conditions (RTP)
-
- Common Reagents Long Term Storage
-
- No Specialized Catalysts
- Yang, Y.-C., Chemical Detoxification of Chemical
Nerve Agent VX, - Accounts of Chemical Research, 1999, 32, 109-115.
3Oxidative Pathways
-Most attractive oxidant - O2 from air -CxHyXz
O2 CO2 H2O HX (unbalanced) ?Glt0
-Room temperature oxidations by air are
kinetically slow -enzymatic or enzyme-mimics
-Partially reduced O2 (Reactive Oxygen Species)
4Reactive Oxygen Forms
HO-OH b.o. 1 ? 50 kcal/mol
5Partially Reduced Oxygen
6That Last Step The Fenton Reaction
-Reduction of HO-OH H2O2 FeII FeIII HO-
HO. HO. e- HO- Eo 1.8 volts
-HO. reacts with organics with diffusion limited
kinetics
-Possible Roles for O2.- 2O2.- 2H ? H2O2
O2 O2.- FeIII ? O2 FeII
7The Proposed System
Red reducing agent, consumed MII/III O2
activation redox catalyst MII/III Fentons
Reagent
8Putting the System Together The Reducing Agent
Considerations -Costs -Kinetics -Environmental
Ered0
Zero-valent metals Fe ? Fe2 2e- -0.44
volts Ascorbate Ascorbate ? dehydroxyascorbate
2e- 0.154 volts (pH 4)
9Putting the System Together Oxygen Activation
Agents
RTP O2 activation
Biological Systems -cytochrome p450. Chemical
Systems -non-heme iron complexes (cost?) Que,
L. JACS 2003, 125, 2113-2128 -FeIIEDTA
oxidation by O2 Van Eldik, R. Inorg. Chem,
1997, 36, 4115-4120
10Putting the System Together Fentons Reagent
- H2O2 e- ? HO- HO? Ered0 0.26(pH 6) to
0.08(pH 3) V - FeIIIEDTA e- ? FeIIEDTA Ered0 0.1 V
- FeII/IIIEDTA is a classic Fentons Reagent
- Used in DNA footprinting studies
- Can FeII/IIIEDTA do both O2 activation
- and the Fenton reaction?
11Summary of Van Eldik Study
FeIIEDTAH(H2O) O2 ? FeIIEDTAH(O2)
H2O FeIIEDTAH(O2) ? FeIIIEDTAH(O2-) FeIIIEDTAH(O
2-) FeIIEDTAH(H2O) ? FeIIIEDTAH(O22-)FeIIIEDTAH
H2O FeIIIEDTAH(O22-)FeIIIEDTAH H2O
2H ? 2FeIIIEDTAH(H2O) H2O2 2FeIIEDTAH(H2O)
H2O2 ? 2FeIIIEDTAH(H2O) H2O Proposes H2O2 as
intermediate Saw no evidence of H2O2
Van Eldik, R. Inorg. Chem, 1997, 36, 4115-4120
12Our System
- System Consists of Fe(0) 20 mesh, EDTA, Air
Water - Proposed dioxygen activation schemes.
- Heterogeneous activation at the Fe(0) surface.
- Homogeneous activation by Fe(EDTA). Reaction
stoichiometries are not balanced and only
representative of likely processes. - Heterogeneous activation producing ferryl.
13Method for Detection of Facile Oxidant from O2
Actiavtion
Thiobarbituric acid-reactive substances (TBARS)
assay Nonselective detection of oxidizing
species.
532 nm
14TBARS Results
Results of HO radical trapping by
deoxyribose/thiobarbituric acid system forming a
chromgen (532 nm). The conditions were 30 minutes
of reaction time with 0.1 g 40-70 mesh Fe(0),
under aerobic conditions. Other conditions stated
below.
15Summary of the New System
Consists of Fe(0), EDTA, Air, and Water Fulfills
Several Requirements Inexpensive Reagents
Long Shelf Life Nontoxic No Precious Metal
Catalysts No Special Reaction
Vessels RTP Possibility for Portability
Field Destruction
16Xenobiotic Oxidation Studies
H2O2
O2 2H
EDTA
Iron particles 0.1-1 mm
FeIIEDTA
Fe2
FeIIIEDTA HO- HO.
Aqueous Xenobiotic
CO2 H2O
17Xenobiotic Oxidation Studies
Chlorophenols recalcitrant and oxidatively
stable Malathion Surrogate for
organophosphorous compounds Kinetics Intermed
iates Final Products -50/50 Ethyl
Acetate/Hexane GC-FID -Direct Aqueous
LC-GC -Ion Chromatography
18Oxidation of Chlorophenols
- 0.5 g of 40-70 mesh Fe(0)
- 10 mL of solution
- 0.32 mM EDTA
- 140 ppm 4-chlorophenol
- 4 hour reaction time
- GC and LC-MS
- RTP
19Reaction Vessel
Air flow
2.0 mL 50/50 hexane/ethyl acetate (extraction
only)
10.0 mL water
pH 5.5 6.5, unbuffered.
0.44mM EDTA
0.44mM Xenobiotic
Stir bar
0.5g Fe 20 or 40-70 mesh
204-CP Degradation Kinetic Studies
Pseudo first-order rate constant -1.11 /hr.
0.5-g 40-70 mesh Fe(0) 0.72 mM EDTA 0.54 mM
4-chlorophenol Aerobic conditions
21Summary of the degradation of the chlorophenols
in this study
. All runs included 0.5 g of 40-70 mesh Fe(0) in
10 mL of solution.
22Organophosphorous Agents
Malathion
VX
Sarin, GB
23Control Studies
- Control experiments conducted using
- No EDTA
- No O2
- No Fe0
- showed no malathion degradation.
-
- Post reaction extractions of the iron solids
using - Ethyl acetate
- Toluene
- Butanol
- Hexane
- showed the absence of any organics absorbed to
the iron surface.
24Summary of Identified Intermediates
DES
malathion
max 4-6 hrs
unknown product max 2-3 hrs
malaoxon
PO43- SO42-
Max 7 hrs
25Kinetics of Malathion Degradation
Malathion
Diethyl Succinate (DES)
GC/FID chromatograph, error bars indicate the
standard deviation between three measurements of
each sample.
26Malaoxon
27Unidentified Intermediate
MW 410 g/mol
28Ion Chromatography of other Ionic Products and
Intermediates
29Summary of Intermediates
30Kinetically stable organic species in the
presence of aqueous Fe(0)/EDTA/O2.
24 hour products for the degradation
of -EDTA -Malathion -4-chlorophenol
-pentachlorophenol -phenol
31pH Control and Possible Role
Self Buffering at pH 5.5 production of organic
acids Optimal pH range 3-6
32Technical Summary
- Ability to degrade organic pollutants
- Under room temperature, atmospheric pressure
conditions -
- Inexpensive Reagents Iron particles, water, air
EDTA - Unspecialized reactors
- Process is easily transportable, iron particles
EDTA - Strong possibility of scale-up
- Example of a Green Oxidant
33Scientific Summary
- First example of abiotic RTP activation of O2
able to oxidize destructively organics - Control experiments indicate process is dependent
on Fe(0), EDTA, air, and water -
34Future Investigations
- Mechanisms Understanding the process, C balance
- Kinetics Speeding up the process
- Homogeneous Systems
- Search for an oxidatively stable iron
chelate/organic solvent - Basic organic chemistry oxidizable and
nonoxidizable functional groups - Application Scale-up
35Desorption Studies
36Time 0 hrs
EDTA
Malathion
Reaction Conditions 0.44mM Malathion 0.44mM EDTA
0.5g FeO O2
HCO3-
propionic acid
oxalate
Time 13 hrs
Iminodiacetic Acid