Adsorption/Desorption of Pollutants to Nanoparticles

Mason Tomson, V. L. ColvinXuekun Cheng, Y. Gao, R. Wahi, A. T. Kan

Center for Biological and Environmental NanotechnologyCivil and Environmental Engineering and Chemistry

DepartmentsRice University

September 15, 2003

Adsorption/Desorption Hysteresis

Reaction Uptake

BiodegradationVolatilization

DesorptionToxicity

Black Carbon

Sorption/Desorption HysteresisdespK

adspK>

0.00.51.01.52.02.5

Solid

Pha

seC

onc

(µg/

g)

0.0 0.2 0.5 0.8 1.0

Solution Phase Conc (µg/ml)

Naphthalene/LulaDesorption

Adsorption

Rev. Irr.

max

max

Water

~0.01

102030

0.02 (µg/

ml)

(µg/

g)

"Unweathered,non-remediated, or freshly

contaminated"

"Weathered,remediated, or aged"

Sediment

Rev. Irr.1 02 0

4 05 06 0

3 0

max

max

Rev.

~

Water

0.01

102030

0.02

Irr.

1020

405060

30

Irr.Rev.

Sediment

(µg/

ml)

(µg/

g)

Adsorption/Desorption Hysteresis

0.1

10

103

105

10-7 10-5 0.1 10 1000Solution Phase Conc (mg/L)

102

105

104

103

106

K OC=10

7 Boston Harbor:1. Phenanthrene2. Pyrene3. Cl 5-PCB4. Cl 6-PCB

Lake Charles, LA :5. Cl 2-Benzene6. Cl 3-Benzene7. Cl 4-Benzene8. Cl 6-Benzene9. Cl 6-Butadiene

Example:MCL (WQC) forp-Cl 2-Benzene withKoc ~1000So

lid P

hase

Con

c(m

g/K

g -O

C)

AqueousSolubility (mg/L)

IrreversibleSQC

ReversibleSQC

10-3

Tolu

ene

Phen

Nap

h

PCE

TCE

Ben

DD

TC

l 6-B

en

Cl 2-

Ben

Cl 4-

Ben

Cl 6-

But

Cl 2-

PCB

Cl 4-

PCB

Naphthalene Adsorption onto Original C60 Particles

E. Ballesteros et al. 2000 J. Chromatography A —

Little adsorption from naphthalene aqueous solution onto fullerene C60 particles was found...

Kp ~ 10

Flow In:Naphthalene

0.1ug/mlFlow Out:

Naphthalene

22% Naphthalene adsorbed

Fullerene C60Column

Carbon Nano-Particle Transport

C60 smallaggregates

Toluene extraction

C60 colloidalparticles

TolueneNo extraction

C-18 Sep-Pak®

No adsorption

Adsorption of Organic Contaminants from Solution to C60 Fullerene

Batch Adsorption/Desorption Study:

C60 largeaggregates

C60 smallaggregates

C60 colloidalparticles

UV/Vis Spectrum of C60 in TolueneSampled from small aggregates

407nm

424nm690nm

Naphthalene-Carbon Adsorption Isotherms

(1) Activated carbon (2) Large aggregatesq=105.20C0.31

0

200

400

600

800

1000

0 1 2 3 4

Solution Phase C (ug/ml)

Solid

Pha

se C

(ug/

g)

q=102.39C

(3) Colloidal C60

020000400006000080000

100000120000

0 0.1 0.2 0.3Solution Phase C (ug/ml)

Solid

Pha

se C

(ug/

g)

(3) Small aggregates

02000400060008000

100001200014000

0 0.1 0.2 0.3 0.4Soultion Phase C (ug/ml)

Solid

Pha

se C

(ug/

g)

q=104.27C0.44

0

5000

10000

15000

0 1 2 3Solution Phase Conc. (mg/ml)

Solid

Phas

e Con

c. (m

g/g)

q=103.75C

Adsorption/Desorption of Naphthalene(Small Aggregated and Colloidal C60 Particles)

0

2000

4000

6000

8000

10000

12000

0 0.1 0.2 0.3 0.4Solution Phase Conc. (mg/ml)

Solid

Pha

se C

onc.

( m

g/g)

Adsorption

0

2000

4000

6000

8000

10000

12000

14000

0 1 2 3

Solution Phase Conc. (mg/ml)

Solid

Pha

se C

onc.

(mg/

g)

Adsorption

DesorptionDesorption

Small aggregates Colloidal C60

Adsorption/Desorption of Naphthalene to Small Aggregated C60 Particles

00.050.1

0.150.2

0.250.3

0.35

0 10 20 30 40 50 60 70Desorption Time(d)

Solu

tion

Phas

e C

(ug/

ml)

0%

2%

4%

6%

8%

10%

12%

0 10 20 30 40 50 60 70Desorption Time(d)

% D

esor

bed

#1#3

Adsorption and Desorption of Organic Contaminants

102

105

104

103

106

K oc= 10

7

Solid

Pha

se C

onc.

(mg/

Kg

-OC

)

0.1

10

103

105

10-7 10-5 0.1 10 1000Solution Phase Conc. (mg/L)

Boston Harbor:1. Phenanthrene2. Pyrene3. Cl5-PCB4. Cl6-PCB

Lake Charles, LA:5. Cl2-Benzene6. Cl3-Benzene7. Cl4-Benzene8. Cl6-Benzene9. Cl6-Butadiene

Phen

Cl 2-

PCB

Nap

hC

l 2-B

enPC

ETo

luen

eTC

EB

en

DD

TC

l 6-B

enC

l 4-PC

B

Cl 6-

But

Cl 4-

Ben

Example:MCL (WQC) forp-Cl2-Benzene withKoc ~1000

AqueousSolubility (mg/L)

IrreversibleSQC

ReversibleSQC

10-3

Naturally occurringsoil organic carbon

10-7 10-5 10-3 0.1 10 1000

ads

des

Naphthalene

C60 Fullerene 105

103

10

0.1

Solution Phase Conc. (µg/ml)

Solid

pha

se c

onc.

(µg/

g)

Solid Lines Represent the Rice University Dual Equilibrium Model

Carbon Nano-Particle Transport

C60 smallaggregates

Toluene extraction

C60 colloidalparticles

TolueneNo extraction

C-18 Sep-Pak®

No adsorption

What Happened During Adsorption?

Naphthalene

adsorption aggregation

Clusters Aggregation &

Naph. Entrapment

Small Fullerene Aggregates

Naphthalene Adsorption

What Happened During Desorption?

“Loosely” Adsorbed

Naphthalene

desorption

“Entrapped”Naphthalene

Possible Explanations

Two parts of adsorption/desorption:

q1: adsorption onto surfaces

q2: entrapment in clusters

q1 account for ≈ 11% adsorption;

q2 account for ≈ 89% adsorption

Possibility of adsorption/desorption hysteresis

Adsorption/desorption hysteresis needs further study

Adsorption of Cadmium to Anatase Nanoparticles

Adsorption/Desorption of Cd to Soil

01234567

0 0.05 0.1Solution Phase Cd Conc.

(mmol/L)

Solid

Cd

Con

c. (m

mol

/kg)

0102030405060708090

100

3 4 5 6 7 8

pH

% C

d ad

s or

des

Reversible Irreversible

AdsDes

Physical Characteristics of Anatase

Sample CrystallinePhases Detectedby XRD

Specific SurfaceArea, (m2/g)

Mean ParticleSize (nm)

AmorphousTiO2 Detectedby TG/DTA

Sigma Anatase 10.8 145 noneAlfa Aesar Anatase 11.2 139.5 noneTiNano Anatase 39.8 39.2 noneP-25 Anatase (80%),

rutile (20%)46.9 33.3 none

RHT 47 Anatase 75.1 20.8 noneRHT 24 Anatase 108.5 14.4 --RHT 45 Anatase -- 9.45 --

RHT 43 Anatase -- 7.72 --

RHT 69 Anatase 195.3 8.0 noneRHT 127 Anatase 193.4 8.08 none

TEM Images of Anatase

Large CrystalsNanoparticles (RHT-69)

100 nm20 nm

Adsorption of Cadmium to Large and Nano-Anatase

20 nm

0

1

2

3

4

0.0 0.5 1.0

C (mmol/ml)

q (m

mol

/m2)

Nanoparticles

100 nm

01234

0.0 0.5 1.0C (mmol/ml)

q (m

mol

/m2)

Large crystals

Langmuir Adsorption Isotherm Parameters

Solid Qmax

(µmol/m2)

b

(ml/µmol)

Qmax·b

(ml/m2)

σQºc

(ml/m2)

σbc

(ml/µmol)

Rc

Sigma andAlfa Aesara

3.19 108.7 346.75 0.12 29.2 0.978

P-25 andTiNanob

3.50 3.70 12.94 0.10 0.40 0.985

RHT-47 3.25 8.94 29.02 0.15 1.33 0.991

RHT 69 2.55 7.71 19.7 0.12 1.06 0.991

Adsorption/Desorption Reversibility

050

100150200250300350400

0 0.1 0.2 0.3 0.4 0.5

Cd in solution (mmol/l)

Cd

ads

(mm

ol/k

g)RHT 69

Nanoparticles

0

5

10

15

20

25

30

0 0.04 0.08 0.12

Cd in solution (mmol/l)

Cd

ads (

mm

ol/k

g)

Large Crystals

Sigma

Electrochemical Propertiesg of solid added Initial

pHFinalpH 2m

pH∆

0.8g Sigma Anatase 7.50 6.59 0.1050.2g Tinano 40 7.51 6.61 0.1132.0g Sigma Anatase 7.30 6.37 0.0430.5g Tinano 40 7.32 6.33 0.050

0.8g Sigma Anatase 6.03 5.99 0.0020.2g Tinano 40 6.02 5.92 0.0072.0g Sigma Anatase 6.01 5.97 0.0050.5g Tinano 40 6.00 5.86 0.012Reported pzc: 5.8 - 6.1 pH

Surface Charges and pH Adsorption Edge

-0.25

-0.15

-0.05

0.05

0.15

0.25

3.5 4.5 5.5 6.5 7.5pH of Suspension

σ (C

/m2

solid

) TiNanoSigma

Potential Titration TiO2 suspension

0

20

40

60

80

100

3 4 5 6 7 8 9 10

pH of Solution

% C

d ad

sorp

tion

SigmaTiNano

Cd adsorption vs. pH

Summary

States of aggregation of nanoparticles may change in various aqueous environmentAdsorption of contaminants to the surfaces of nanoparticles is very strongAdsorption/desorption of organic compounds to nanoparticles might be hystereticAdsorption/desorption of heavy metals onto/from nanoparticles are predictable based on surface area normalized sorption isothermNanomaterials in natural aqueous environments may affect the fate and transport of contaminants substantially

Future

Responsible UseRemediation