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Imprinted Nanoporous Organosilicas for Selective Adsorption offor Selective Adsorption of
Nitroenergetic Targets
B.J. White, P.T. Charles, B.J. MeldeCenter for Bio/Molecular Science and Engineering
N l R h L b t C d 6900Naval Research Laboratory; Code 6900Washington, DC
Synthesis of Organosilicas
• Surfactant-directed• Acid-catalyzed condensationy• Tunable characteristics
• Selection of surfactant• Selection of precursors• Incorporation of imprint template
Precursors
Bridging TerminalBridging Terminal
(H3CO)3SiSi(OCH3)3
• Selected to provide structural and binding characteristicsp g• Combining multiple structures often offers the best compromise• May also be used to provide sites for post synthesis modifications
Precursors355 m2/g
d (m
g/g) 6
NT
Bou
nd
2
4
70 30
1004 m2/g
TN
0
2 70:30
1180 m2/g
Johnson et al. Langmuir (2008) 24, 9024
0DiethylbenzeneEthane Ethane +
Diethylbenzene
• Increasing DEB concentration provides enhanced TNT binding capacity
• Trade off is in loss of material surface area and organizationg• Also observed is a loss in selectivity upon increase in DEB • Design of material requires compromise between total capacity,
selectivity, and structural characteristics
Surfactant
Brij 76; Pores ~30 Å Pluronic P123; Pores ~75 Å
Mesitylene
• The surface is structure directingThe surface is structure directing• Variations provide control of pore size and organizational character
• Brij®76 - Polyoxyethylene (10) stearyl ether• Pluronic P123 - Poly(ethylene oxide)-b-poly(propylene oxide)-b-
poly(ethylene oxide) triblock copolymer• May be combined with a swelling agent
• Mesitylene
Imprinting
Surfactant Analog
Johnson et al. Langmuir (2008) 24, 9024
• Similar to molecular imprinting of polymers
g ( ) 4, 9 4
p g p y• Template is incorporated into surfactant micelles• Upon surfactant extraction, provides sites on pore wall that are
more favorable to target interactions
Imprinting
Targetm
g/g)
3
4TNT
TargetMixture
TNT
Bou
nd (m
2
3 TargetMixture
TNT
1
Johnson et al. Langmuir (2008) 24, 9024
0No Imprint Imprinted
• Comparison of target binding from single and multi-component solutions
• TNT binding is reduced in mixture for non-imprinted materialg p• TNT binding is not reduced in imprinted material
Reducing Back Pressure
SEM t i l SEM hi hi l t i lSEM – mesoporous material SEM – hierarchical material
10 μm 10 μm
50 nm
• Use of Pluronic P123 with swelling agent to produce macropores
TEM – mesopore order in hierarchical materialJohnson et al. In preparation (2008)
Use of Pluronic P123 with swelling agent to produce macropores• Mesoporous – pores of 2 to 50 nm• Macroporous – pores of greater than 50 nm
• Results in reduced surface area• Provides the necessary reduction in back pressure to allow
application in column formats
TNT/DNT Material
50 50 DEB BTE i i t d i 12 6% difi d Pl i P12350:50 DEB:BTE imprinted using 12.6% modified Pluronic P123Hierarchical structure
35 Å mesopores (H3CO)3SiSi(OCH )
BTE
P) Nitrogen Sorption366 m2/g0.261 cm3/g
Si(OCH3)3
DEB
orbe
d (c
m3 /g
STP
50
Nitrogen Sorption
8E4
ume
Nitr
ogen
Ads
XRD Spectrum
Inte
nsity
4E4
6E4Relative Pressure (P/P0)
0.0 0.2 0.4 0.6 0.8 1.0Vol
u
)
Pore Size Distribution
2θ0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0E0
2E4
V/d
log(
D) (
cm3 /g
)
0.5
1.0
Johnson et al. In preparation (2008)
2θ
Pore Diameter (Α)0 50 100 150 200
dV
0.0
RDX Material
40 50 10 DEB BTE PTS40:50:10 DEB:BTE:PTSHierarchical structure
43 Å mesopores (H3CO)3SiSi(OCH )
BTE278 m2/g0.226 cm3/g
Si(OCH3)3
DEB
PTS
STP)Pore Size Distribution Nitrogen Sorption
50
Ads
orbe
d (c
m3 /g
S
og(D
) (cm
3 /g)
1.0
0.0 0.2 0.4 0.6 0.8 1.0Vol
ume
Nitr
ogen
A
0 50 100 150 200
dV/d
lo
0.0
0.5
Relative Pressure (P/P0)
V
Pore Diameter (Α)
Johnson et al. In preparation (2008)
Target Binding – Batch Experiments
/m2 ) 9E3
/m2 ) 3E4
Imprinted 50:50 DEB:BTE 40:50:10 DEB:BTE:PTS
RD
X b
ound
(μg/
3E3
6E3
TNT
boun
d (μ
g/
1E4
2E4
[RDX] (μM)0 50 100 150
0E0
[TNT] (μM)0 50 100 150
0E0
/ 2
Johnson et al. In preparation (2008)
Saturation capacity = 11 mg/m2
Association constant = 7.69e‐3 μg‐1Saturation capacity = 50 mg/m2
Association constant = 2.44e‐3 μg‐1
• Equilibrium batch experiments• Parameters determined based on Langmiur-Freundlich model of a
general binding isotherm for identical binding sitesgeneral binding isotherm for identical binding sites
Columns
0 8
1.0
Imprinted 50:50 DEB:BTEActivated Charcoal 0 8
1.040:50:10 DEB:BTE:PTSActivated Charcoal
Imprinted 50:50 DEB:BTE 40:50:10 DEB:BTE:PTS
TNT
C/C
o
0.4
0.6
0.8 Activated Charcoal
RD
X C
/Co
0.4
0.6
0.8 Activated Charcoal
0 10 20 30 40 50 60 70
0.0
0.2
0 10 20 30 40 50 60 70 80
0.0
0.2
Target Applied (mg) Target Applied (mg)
Johnson et al. In preparation (2008)
• Column format using 200 mg of materials• 4 mL/min flow rates with 3 mL additions of 10 μM target solution
Soil Extraction
Johnson et al. In preparation (2008)
• Samples obtained from USAERDC hot and cold grids • Column format using 25 mg of material• Gravity driven flowGravity driven flow• Extraction into deionized water• Elution using methanol
Soil Samplespm
)
54 Following ConcentrationAs Extracted
Concentrations Enhanced:RDX – 6.25x1 3 5-trinitrobenzene – 1 93x
ncen
tratio
n (p
6
521,3,5 trinitrobenzene 1.93x2,4,6-trinitrotoluene – 30.6x
Targets enhanced from d t t bl
Targ
et C
on
2
4non-detectable:
tetryl2-amino-4,6-dinitrotoluene4-amino-2,6-dinitrotoluene
h l
0
RDX
TNB
Tetryl
TNT2-A
DNT4-A
DNT
DNT NTa o ,6 d t oto ue e
2,4- &/or 2,6-dinitrotoluene2-nitrotoluene
Johnson et al. In preparation (2008)2-A 4-A• As extracted and concentrated samples analyzed by HPLC using EPA
Method 8330• Concentration accomplished using Imprinted 50:50 DEB:BTE material• Data presented here are for sample HO-001; soil taken from an old 2,000 lb
bomb crater
Soil Samples
3 NT
4-ADNT2,4-DNT
2-NT4-NT3-NT
ET
tetrylNB
TNT2-ADNT4-ADNT
TAR
GE
HMXRDXTNBDNBtetryl
HO-001
HO-004
HO-006
HO-018
HO-019
HO-020
HO-022
HO-023
HO-024
HO-025
HO-026
HO-027
SAMPLE
HMX
SAMPLE
USAERDC Original AnalysisNRL Analysis – as extracted
Presence of a symbol on the grid indicates detection by the indicated
Johnson et al. In preparation (2008)
NRL Analysis as extractedNRL Analysis – after concentrationNRL Analysis of column effluent
indicates detection by the indicated analysis
Soil Sample Key
HO-001 Old 2,000-lb craterO 00 O d ,000 b c a eHO-004 Old 2,000-lb craterHO-006 Old 500-lb craterHO-018 Low order bomb crater Hot GridHO 019 L d b b t H t G idHO-019 Low order bomb crater Hot GridHO-020 Low order bomb crater Hot GridHO-022 2,000-lb crater Hot GridHO-023 2,000-lb crater Hot GridHO 023 2,000 lb crater Hot GridHO-024 2,000-lb crater Hot GridHO-025 No visible low-order debris Cold GridHO-026 No visible low-order debris Cold GridHO 02 N i ibl l d d b i C ld G idHO-027 No visible low-order debris Cold Grid
Johnson et al. In preparation (2008)
Current Ongoing Effort
• Incorporate materials inline with electrochemical detection methods
• Extract trace level targets from ground water samples obtained from• Extract trace level targets from ground water samples obtained from New Mexico Environment Department, Department of Energy Oversight Bureau
• Compare materials developed for this effort to commercially available materials for nitroenergetic concentration
AcknowledgementsSupport for this research was obtained from the Strategic Environmental Research & Development Program and the Office of Naval Research. The views expressed here are those of the authors and do not represent those of the U.S. Navy, the U.S. Department of Defense, or the U.S. Government.
We gratefully acknowledge the kind assistance of Alan Hewitt (US Army Corps of Engineers, Engineer Research and Development Center) who provided soil samples as well as Kim Granzow and Michael Dale (New
Mexico Environment Department, Department of Energy Oversight Bureau) who provided groundwater samples.