2010 - Chemical & Biomedical Engineering - University of South ...

Technological solutions have
to be developed that are
efficient, environment
friendly, and can be
economically implemented
in large-scale processes.
Dr.Vinay Gupta’s research group
left to right:
Bijith Mankidy,
Chhavi Manocha,
Cecil Countino,
Kristina Tran,
Dr. Gupta,
Rashima Harrinauth,
Fedena Fanord and
Alisha Peterson.
Dr. Gupta - Engineering Novel Hybrid and
Composite Materials
Removal of chemical contaminants
in aqueous streams is a critical challenge
faced by society. Technological solutions
have to be developed that are efficient,
environment friendly, and can be economically
implemented in large-scale
processes. Nanoparticles of metals and
mineral oxides have made it possible to
design and develop improved substrates
for efficient removal of organic and inorganic
contamination, either by sorption
or sequestration mechanisms, or as
a catalyst. The high surface area to volume
ratio due to nanometer size of the
particles and the accompanying physical
and chemical enhancement of surface
properties is one of the key factors behind
the efficiency in remediation. A
major bottleneck in the use of nanoparticles
is that the size of the particle affects
the remediation technology. For
example, in fixed bed reactors the packing
material must not easily clog; similarly
for treatments that use fine
particles in a batch type reactor, a filtration
system is needed to recover the
particles from the liquid effluent. The
nanoparticles, while advantageous for
organic decontamination, rapidly become
an expensive liability due to increased
process complexity, need for
critical process control, and an increased
potential for environmental pollution as
well as cost of chemicals due to incomplete
or inefficient recovery of the
nanoparticles. Strategies such as coatings
of nanoparticles on walls, plates, or
beads are of limited use as they reduce
surface availability of the particles and
pose limitations on transporting contaminants
to the particle surface. Challenges
such as these are being
addressed at the University of South
Florida in the research program led by
Dr. Vinay Gupta. The focus is on engineering
novel materials and constructs
by combining polymers with metallic or
oxide nanoparticles using interfacial
modifications and assimilating the
unique properties of each component.
To eliminate the bottleneck in using
nano-sized photocatalyst for the remediation
of contaminated waters, Gupta’s
research has established a novel and
unique approach where transparent,
cross-linked, porous polymer microspheres
are impregnated with photocatalytic
titanium dioxide (or titatnia)
nanoparticles. Using a simple and easy
mixing technique allows for the preparation
of the microcomposites in an economically
feasible manner and allows the
loading of titatnia to be controlled (J.
Colloid & Interface Science, 116-122,
2007; patent pending). These microcomposites
show rapid sedimentation in minutes,
which is useful for gravity
separation of these particles in applications
such as remediation. The photograph
(right) illustrates photodegradation
of a model contaminant, an organic
dye, using both the microcomposites and
the free titatnia nanoparticles. The photodegradation
is achieved using a commonly
available BLB light bulb that
simulates light in the UVA range (~365 nm),
which is readily available in sunlight. After
the degradation of the dye into carbon
dioxide and water, the free titatnia
nanoparticles remain suspended in the
water but the microcomposites settle rapidly,
which makes them suitable for use in
large-scale clarifiers and sedimentation
tanks. In addition to the practical applications,
Gupta’s research group has also fundamentally
studied the settling behavior of
these microgel-titatnia composites as these
permeable particles provide an interesting
contrast to the sedimentation of solid, impenetrable
spheres (Colloids & Surface A,
111-121, 2008). These particles provide a
suitable experimental system to gain insights
into sedimentation behavior of complex
systems such as permeable particles
and flocs of fine particles held by organic
matter that are of practical significance in
diverse areas such as marine geology,
coastal and ocean science, hydraulic engineering,
and solid-liquid separation technology.
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