adsorption/desorption of pollutants to nanoparticles · 2015. 9. 18. · adsorption/desorption...
TRANSCRIPT
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