imprinted nanoporous organosilicas for selective

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


• 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


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)


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


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)


• Column format using 200 mg of materials• 4 mL/min flow rates with 3 mL additions of 10 μM target solution

Soil Extraction


• 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


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


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.

imprinted nanoporous organosilicas for selective

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