Adsorption/Desorption of Pollutants to Nanoparticles

1
Adsorption/Desorption of Pollutants to
Nanoparticles

• Mason Tomson, V. L. Colvin
• Xuekun Cheng, Y. Gao, R. Wahi, A. T. Kan
• Center for Biological and Environmental
  Nanotechnology
• Civil and Environmental Engineering and Chemistry
  Departments
• Rice University
• September 15, 2003

2
Adsorption/Desorption Hysteresis
Biodegradation
Volatilization
Uptake
Reaction
Toxicity
Desorption
3
Black Carbon
4
Sorption/Desorption Hysteresis
gt
ads
des
K
K
p
p
Desorption
Adsorption
5
(No Transcript)
6
Adsorption/Desorption Hysteresis
7
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
8
Carbon Nano-Particle Transport
9
Adsorption of Organic Contaminants from Solution
to C60 Fullerene
Batch Adsorption/Desorption Study
10
UV/Vis Spectrum of C60 in Toluene
Sampled from small aggregates
407nm
424nm
690nm
11
Naphthalene-Carbon Adsorption Isotherms
(1) Activated carbon
(2) Large aggregates
q105.20C0.31
q102.39C
(3) Small aggregates
(3) Colloidal C60
q104.27C0.44
q103.75C
12
Adsorption/Desorption of Naphthalene(Small
Aggregated and Colloidal C60 Particles)
Small aggregates
Colloidal C60
Desorption
Desorption
Adsorption
Adsorption
13
Adsorption/Desorption of Naphthalene to Small
Aggregated C60 Particles
14
Adsorption and Desorption of Organic Contaminants
Naturally occurring soil organic carbon
C60 Fullerene
105 103 10 0.1
Solid phase conc. (mg/g)
Solution Phase Conc. (mg/ml)
Solid Lines Represent the Rice University Dual
Equilibrium Model
15
Carbon Nano-Particle Transport
16
What Happened During Adsorption?
Naphthalene
adsorption
aggregation
Clusters Aggregation Naph. Entrapment
Small Fullerene Aggregates
Naphthalene Adsorption
17
What Happened During Desorption?
Loosely Adsorbed Naphthalene
Entrapped Naphthalene
desorption
18
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

19
Adsorption of Cadmium to Anatase Nanoparticles
20
Adsorption/Desorption of Cd to Soil
Reversible
Irreversible
21
Physical Characteristics of Anatase
22
TEM Images of Anatase
Large Crystals
Nanoparticles (RHT-69)
23
Adsorption of Cadmium to Large and Nano-Anatase
24
Langmuir Adsorption Isotherm Parameters
25
Adsorption/Desorption Reversibility
Nanoparticles
Large Crystals
RHT 69
Sigma
26
Electrochemical Properties
Reported pzc 5.8 - 6.1 pH
27
Surface Charges and pH Adsorption Edge
Potential Titration TiO2 suspension
Cd adsorption vs. pH
28
Summary

• States of aggregation of nanoparticles may change
  in various aqueous environment
• Adsorption of contaminants to the surfaces of
  nanoparticles is very strong
• Adsorption/desorption of organic compounds to
  nanoparticles might be hysteretic
• Adsorption/desorption of heavy metals onto/from
  nanoparticles are predictable based on surface
  area normalized sorption isotherm
• Nanomaterials in natural aqueous environments may
  affect the fate and transport of contaminants
  substantially

29
Future

• Responsible Use
• Remediation