Nanotechnology for Treatment of Contaminated Water

D. Bhattacharyya (speaker)*, J. Xu, S. Lewis, L. Bachas, B. Hennig, and D. Meyer

UK NIEHS-SBRP ProgramUniversity of Kentucky

Lexington, Kentucky 40506 USA

* email: db@engr.uky.edu* phone: 859-257-2794

Joint NIEHS SBRP-WETP Technical Workshop April 3-4, 2008

Natcher Conference Center, NIH CampusBethesda, MD

Detoxification of Chloro-Organics, such as TCE, PCB (At Room Temperature)

Reduction pathway for Chlorinated Compounds

PCB →

BiphenylTCE → Ethane

Systems:Zerovalent metals (Fe), Bimetallic system (Fe/Pd, Fe/Ni), Polymer Platform

Oxidation of Chlorinated Compounds

Products: CO2 , Organic Acids,Potential chloro-intermediates

Systems : Chelate Modified Fenton Reaction

On-site enzymatic H2 O2 generation

Nanosiz

ed M

etals Hydroxy-Radical

& Chelates

CombinedPathway

H2 O2

Fe2+ + nontoxic chelate

TCE, PCB, etc

Ground level

Groundwater Remediation Using Combined Strategies For Reduction and Oxidation

Fe, Fe/Pd, Fe/ Ni

Reduction Oxidation

Groundwater

Dechlorination Products and/or Intermediates

Ethane

Organic Acids and/or CO2

Non-dissolved CO2

Enhanced downstream bio- attenuation of products

because of biodegradable chelate (gluconic acid, citrate)

Detoxification of TCE and PCBMetal Nanoparticles

Solution Phase

Synthesis

Polymer Domain

Fe0 Phase Inversion

Ion- Exchange

Supported*

Fe0, Fe0/Ni, or Fe0/Pd

*eliminates worker exposure

(Bimetallic via Postcoating)

TCE

Ethane

Fe0/Ni, Fe0/Pd

NaBH4

NaBH4

PCB

Biphenyl

Background (membrane-based nanoparticle synthesis)

•Prevent particles agglomeration by polymer network

•Control particle size and assembly •Convective flow•Recapture of dissolved metal ions

Fe nanoparticles synthesized in solution phase. Wang et al., Environ. Sci. Technolo. 1997, 31, 2154

Ag nanoparticles in PAA/PAH multilayer films. Wang et al., Langmuir 2002, 18, 3370

Nanoparticle synthesis in aqueous phase

Nanoparticle synthesis in membrane phase

Particle agglomeration and growth in solution without stabilizing agent

+++

+

+++

++

++

++

++ +

+

+

+

reduction

++++

++

++

++

reduction growth agglomeration

NaBH4

Cu nanoparticles in COOH functionalized polyimide film. Thermal process with H2 Ikeda et al., J. Phys. Chem. B 2004, 108, 15599

Synthesis of Nanostructured Metals in Functionalized Polymers for Detoxification of Chlorinated Organics

Support Membrane (MF, UF): PVDF, PES

Dip-coating PAA or In- situ polymerization of acrylic acid

PAA functionalized membranes

FeCl2 , pH = 5

Fe2+

Fe2+

Fe2+

Fe2+

Fe2+

Fe2+

Fe2+Element Atom%C (K) 64.21 F (K) 22.17Fe (K) 3.01 O (K) 10.62

CO

O

Fe2+

C O

O

SEM-EDX

Pd/Ni coating

TEM-EDXTEM image

Cou

nts

Energy (keV)108642

Pd

Fe

FeFe

O

C

Cu

Cu

Fe = 97.9 wt% Pd = 1.9 wt%

Core/Shell structure

50 nm

Fe Pd

STEM-EDS Mapping

NaBH4

Pore size: 50~500 nm

* C C

H

H F

F* H2C CH

C

**

OH

O

Polyvinylidenefluoride (PVDF)

Pd or Ni

Polyacrylic acid (PAA)

50 nm

EDS Mapping

HRTEM

Fe

Pd

Fe/Pd Nanoparticles Characterization

Electron diffraction pattern

Pd

Fe

{110}

{200}

{210}{222}

Pd

Fe/Pd (Pd = 2.3 wt%) nanoparticles

Body center cubic (BCC) crystal structure of Fe0

(Suslick, Fang, Hyeon, J. Am. Chem. Soc. 118, 11960-11961, 1996)

0.0 0.5 1.0 1.5 2.0 2.50.00

0.04

0.08

0.12 TCE

Con

cent

ratio

n (m

M)

Time (h)

Ethane Mass balance Cl-/3

0.0 0.2 0.4 0.6 0.80

2

4

6

8

10

-Ln(

C/C

0)/ρ

m

Time (h)

kobs = 11.2 l h-1 g-1

TCE Dechlorination by Nanoparticles

Fast and complete degradationto ethane, no toxic intermediates

0 1 2 3 50 510

2

4

6

8

10

12

TCE

con

cent

ratio

n (m

g/L)

Time (h)

TCE spiking

Longevity of Nanoparticle Reactivity

•Fe/Ni (Ni =25 wt%) in PAA/PVDF membranes •Metal loading: 0.08g/20ml•16 cycles of TCE dechlorination

Metal loading:4.5mg/20mLFe/Ni (Ni = 25 wt%)

:Pd/NiSecond metal

Catalytic hydrodechlorination

Fe2+

H*

EthaneTCE

Room temperature

?

Dechlorination of Polychlorinated Biphenyls (PCBs)

PCB 77 (3,3’,4,4’) dechlorination by Fe nanoparticles at room temperature (from Lowry, et al., Environ. Sci. Technol. 2004, 38, 5208)

Metal loading: 4 g/LkSA : 6.3×10-8 L h-1 m-2

t1/2 : 73 daysNegligible biphenyl formation

0.0 0.5 1.0 1.5 2.0 2.50.000

0.015

0.030

0.045

0.060

Con

cent

ratio

n (m

M)

Time (h)

PCB77 (3,3',4,4') PCB37 (3,4,4') PCB35 (3,3',4) PCB15 (4,4') PCB12and13 (3,4' and 3,4) PCB11 (3,3') PCB3 (4) PCB2 (3) Biphenyl Carbon Balance

Metal loading: 0.8 g/LPd = 2.3 wt%kSA : 0.11 L h-1 m-2

t1/2 : 20 minComplete biphenyl formation

PCB 77 (3,3’,4,4’) dechlorination by membrane based Fe/Pd (Pd=2.3 wt%) nanoparticles at room temperature

Cl Cl

Cl

Cl

PCB 77 (3,3’,4,4’)

Aspects to Address for Successful TCE Dechlorination Using Direct Injection of

Nanoparticle Systems• What composition and metal loading are necessary for

rapid and efficient TCE dechlorination? (batch data)• Will the presence of non-chlorinated chemical species

present in Paducah groundwater and soil alter the performance of Fe-based nanoparticle dechlorination systems? (batch and column experimental data)

• What impact, if any, will dissolved oxygen have on dechlorination kinetics? (batch data)

• What type of mobility will nanoparticles have while moving within plumes? (theoretical modeling)

Dechlorination of TCE in Deoxygenated Paducah Water Using Fe/Pd Nanoparticles with Variable Metal Conditions:

C0 = 20.5 mg/L; pH = 5

0.000.100.200.300.400.500.600.700.800.901.00

0 0.2 0.4 0.6 0.8 1 1.2

Time (h)

TCE,

C/C

0

1 wt% Pd; 1.0 g/L

1 wt% Pd; 0.24 g/L

0.5 wt% Pd; 1.0 g/L

1 wt% Pd ~ 0.5 monolayer

Packed Column Studies for Simulated Groundwater Injection

3-in ID Tube

4ft

1’

1.5’

2.0’

2.5’

3.0’

0.25”Sample

Port(PTFE)

0.25”Outlet

(PTFE)

0.5’

3.5’

3-in ID Tube

4ft

1’

1.5’

2.0’

2.5’

3.0’

0.25”Sample

Port(PTFE)

0.25”Outlet

(PTFE)

0.5’

3.5’

Preliminary Results

Column Depth (ft) C/Co0.5 0.1852 0.080

Column Flowrate = 260 ft/day

Fe/Pd (0.5 wt%) = 0.4 g/L

Initial TCE = 46 ppmCirculation Time = 4 h

Liquid Volume = 2.25 L

Paducah Gravel

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 0.5 1 1.5 2 2.5 3 3.5

Column Depth, (ft)

TCE

(C/C

0), C

l- (C

/CM

ax)

24 h TCE48 h TCE24 h Cl-

Packed Column Studies: Flowrate = 82 ft/day; Metal Loading = 0.46 g/L Fe/Pd (0.5 wt%);

C0 = 25 ppm TCE; pH =7.0

Examination of Material Usuage for the Reduction of 400 ppb TCE Using Fe/Pd Nanoparticles

Time Basis 24 h kSA 1.30E-01 L.m-2.h-1 (Fe + 0.5 wt% Pd)Treatment Diameter 400 ft Fe/Pd loading 0.25 g/LTreatment Depth 20 ft mass Fe/Pd 9,433 g/h = 20.753 lbs/hAsssumed Porosity 0.4 Surface Area 30 m2 metal/gTreatment Area 125,664 ft2 Loading 7.5 m2 metal/LTreatment Volume 2,513,274 ft3

Treatment C.S. Area 3,200 ft2 TCE 400 ppbGroundwater Velocity 10 ft/day

0.42 ft/hr CTCE @ 1h 0.000 ppbVolume per hour 1,333 ft3/h TCE reacted 1.15E-01 moles/h

37,733 L/h

Fe:TCE ratio 4:1moles Fe consumed 4.59E-01

mass Fe consumed 25.66 g/h0.056 lbs/h

Fe remaining 9,407.67 g/h20.697 lbs/h unused

Note: one can treat 38000 liters of water with 26 g of nano Fe particles

Detoxification by Chelate-Based Modified Fenton Reaction

• Controlled release of Fe2+

• Prevent Fe(II) oxidation • At near neutral pH, prevent Fe(OH)3 precipitate by

complexing with Fe(III)• Have a better H2 O2 utilization during the reaction• Hydroxy radical and superoxide* radical formation near

neutral pH operation• Potential biodegradation enhancement• Chelate can also be immobilized in nano-particles

Why Chelate-Based Modified Fenton’s Reaction?

*Superoxide Radical Formation: •+→+• 2222 HOOHOHOH−+ •+→• 22 OHHO

Required Materials for Chelate-Based Modified Fenton Reaction

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Citrate Ferrous Sulfate Hydrogen Peroxide

0

1

2

3

4

5

0 10 20 30 40 50H2O2 Consumed (mmol)

TCE

Deg

rade

d (m

mol

)

L/Fe = 3.0 pH = 5.2

L/Fe = 0.5 pH = 6.8

L/Fe = 0.0 pH = 7.4

TCE Degradation as a Function of Peroxide Consumed for Varying Citrate (L)-to-Fe Ratios Showing the Potential Reduction in Peroxide Needs for

Chelate-Based Systems

Increasing L

The Challenges of DNAPL1.) TCE droplets dispersed in the aqueous phase will act as a source of TCE and shrink as mass is lost to the aqueous phase. The mass transfer between phases may have substantial impact on the observed reaction time for both oxidation and reduction.

TCE Droplet

Saturated Aqueous Phase (Reaction Zone)

TCE Droplet

2.) If DNAPL droplets are dispersed within soil and rock, they may require much greater reaction times for direct treatment. To overcome this problem, surfactant addition can potentially be used to mobilize the DNAPL from the sediment. Laboratory packed columns operating under trickle-flow can be used to examine this phenomenon.

Oxidation or ReductionOxidation

or Reduction Products

Dispersed DNAPL Droplets

DNAPL Extraction using surfactant injections

Dispersed DNAPL Droplets

Chelate-Modified Fenton Reaction (initial pH=7.0, no further adjustments made) Using DIUF Water with DNAPL (2000ppm

TCE) and Varying Fe(II):H2 O2 Molar Ratio

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

Time (hr)

TCE

/TC

E 0

0.0

0.2

0.4

0.6

0.8

1.0

Cl- /C

l- max

1:1:1:4 TCE 1:1:1:8 TCE TCE Control1:1:1:4 Cl- 1:1:1:8 Cl- Cl- Control

TCE droplets

Acknowledgements

• NIEHS-SBRP Program

• DOE-KRCEE Program

• UK Environmental Research and Training

Laboratory (ERTL) (John May & Tricia Coakley )

• UK Electron Microscopy Facility (Dr. Alan Dozier)

Extra slides

Background (reductive dechlorination at room temperature)

RCl + H* RH + Cl-

Fe0 Fe2+ + 2e-

Fe0 + 2H+ Fe2+ + H2

Reaction mechanism: electron transfer(Matheson et al., Environ. Sci. Technol. 28, 2045-2053, 1994)

(Meyer and Bhattacharyya, J. Phy. Chem, 2007;Xu et al, J.Nanopar.Res. 7, 449-467, 2005)

Fe2+

e-

RCl + H+

Fe0

RH + Cl-

RCl + 2e- + H+ RH + Cl-

RCl + Fe0 + H+ Fe2+ + RH + Cl-

Cl

ClCl Cl

Cl

ClClCl

Cl

ClCH2H2C

(Xu & Bhattacharyya, Environ. Prog., 24, 358, 2005)

Fe2+

e-H2 O

RH + Cl-

Fe0

Pd0

H2

H*

RCl

Bimetallic system

Single Fe0

system

Reaction mechanism: catalytic hydrodechlorination

H2 + Pd Pd-H + H*

Cl

ClCl

CH3H3C

Technology Enhancement: On-site Generation of Chelate and H2 O2

GOx (Oxidized)

FADGLUCOSE

GOx - GlucoseGOx

(Reduced)FADH2

H2 O2

GLUCONIC ACID

HYPOTHESISGluconic acid produced by enzymatic reaction would act as a chelate in Fenton

reaction, and thus allow degradation of TCE & PCBs near neutral pH

On-Site source of peroxideand chelate will eliminate

the need for concentrated chemical Storage by using simpleGlucose as a substrate

MOTIVATION

O2