Adsorption and desorption of hydrocarbons
and heavy metals from C60 and anatase particles
By Mason B. Tomson, Professor, Center for Biological and Environmental
Nanotechnology, Civil and Environmental Engineering Department, Rice University,
Houston, TX 77005.
Phone: 713-348-6048, E-mail: email@example.com
The introduction of large amounts of nanomaterials into ecosystems may
have unforeseeable environmental impacts. Sorption and desorptiona are important
processes which could possibly control the fate and transport of both nanomaterials
and environmental contaminants. The objective of this study is to understand
the impact of nanomaterials on contaminant transport through investigating
the sorptive interactions of pollutants with C60 fullerene and anatase nanoparticles.
The adsorption and desorption of naphthalene and Cd2+ to large and nanometer
scale C60 fullerene and anatase crystals have been studied to determine
the relationship between hydrocarbon and heavy metal adsorption properties
and particle sizes. Adsorption and desorption of naphthalene to/from C60
fullerene solids in different aggregation forms was studied, where C60 was
used as purchased (20-50 µm); dispersed in water by magnetic mixing
(1-3 µm) or by high-energy sonication probe (nanometer sized). Sorption
coefficients could vary by orders of magnitude and have been observed
to relate to different C60 aggregation forms. Sorption/desorption hysteresis,
a common phenomenon observed in natural soils and sediments, was also observed
in this work with naphthalene sorbed to well dispersed C60 aggregates. Data
showed that adsorption and desorption to/from C60 was analogous to that
reported for soils.
Adsorption and desorption of Cd to/from 10 to 140 nm sizes TiO2 anatase
were studied. On a surface area basis, it was found that large and nanometer
scale anatase particles had similar maximum Cd2+ adsorption capacities,
while their adsorption slopes differed by more than one order of magnitude.
The particle-size effect on adsorption is constant over a pH range of 4
to 7.5. The desorption of Cd2+ from both particle sizes is completely reversible.
The adsorption data have been modeled by the Basic Stern model using three
monodentate surface complexes. It is proposed that intraparticle electrostatic
repulsion may reduce the adsorption free energy significantly for nanometer