Post on 27-Apr-2018
Hydrothermal synthesis of TiO2 nanotube/Graphene
oxide composite and its application in photocatalytic
purification of water
Zahra Gholamvand*, Anne Morrissey, Kieran Nolan, John Tobin* School of Biotechnology, Dublin City University, Dublin, Ireland
Email: Zahra.gholamvand2@mail.dcu.ie
Using graphene sheets as a support to prepare
graphene/ TiO2 nanotubes composite by
hydrothermal in-situ synthesis of TiO2 nano-
nanotubes on the surface graphene oxide sheets
Characterizing Graphene and Graphene/ TNTs
composite structurally and physically and obtain
a composite with high conductivity, crystallinty
and surface area
Finding the most efficient composite by changing
the weight percentage of graphene and TiO2 , the
reduction condition of Graphene Oxide (GO) to
Graphene, temperature, PH and calcinations
temperature
Investigate the efficiency of the composite to
adsorb and degrade organic species such as
VOC, pigments and pharmaceuticals
Designing and building up an efficient
photocatalytic system to work under UV and
sunlight
Comparing the photocatalytic performance of the
Graphene- TiO2 composite with other composites
such as zeolite- TiO2, activated carbon- TiO2 and
Dolomite–TiO2
Finding the most economic and efficient system
to remove organic compounds such as
pesticides, volatile organic compounds and
pharmaceuticals from water and waste water
The authors wish to acknowledge the financial support of,
the Marie Curie Initial Training Network funded by the EC
FP7 People Programme, ATWARM (Advanced Technologies
for Water Resource Management).
Electron diffraction pattern SAD of TNT/GO
composite in Fig.6 shows the sharp diffraction
pattern which shows GO reduced partially
during hydrothermal treatment
All TNTs are attached to the GO surface and
there is no free particle in the solution which
increases the composite functionality and it
might be because of functional groups available
on GO surface.
TNTs growth takes place on the graphene
surfaces which encourages the formation of
nano tubes uniformly dispersed on the
graphene surface and also mimics the
topography of GO into a fractal like shape
(SEM image shown in Fig.10)
The dimensions of the composite sheets were
about 3-5 micro-meter both in length and width,
which allows for an easy separation of the
composite with conventional filtration (SEM
image Fig.9).
In the natural PH TiO2 forms solid wire and
they grow uniformly on the surface of GO with
the average length of 1-2 micrometer and 10-
20 nano meter in diameter
Photo-degradation of famotidine as a pollutant
model is shown in Fig.3. Before the
photocatalytic experiment, the suspension of 1
liter solution with a famotidine concentration of
100 mg/lit and 0.2 gr/lit catalyst was
magnetically stirred for 2 h in dark to discount
the adsorption on the catalyst. The rapid
degradation of famotidine over GO/TiO2 is
clearly shown in Fig.11. About 90% of the
famotidine was degraded within 180 min which
is a significant photo-degradation in
comparison with P25 powder and neat TNTs
powder that exhibited less than 50 degradation
over the same time.
After photo-degradation the catalyst can be
removed easily by filtration or settling down in
the reactor this is another advantage of using
composite over TiO2nano powderNatural Energy
usage
Advanced
Technologies
New Materials
Photocatalysis
Abstract Objectives Results Results
Conclusions
Acknowledgment
Fig.2. Degradation mechanism and recombination of
trapped electrons
MethodBackground
Nanocrystalline semiconductors, such as titania,
are important in many energy-saving processes
including: water purification, air purification,
disinfection and self-cleaning.
Over the past decades degradation of organic
pollutants using titanium dioxide has attracted
increasing attention for the purification of
water. One of the newest methods is
combining titanium dioxide and an adsorbent
material to create integrated photocatalytic
adsorbents (IPCAs) which overcome some of
the limitations of TiO2 nano-particles such as
low photocatalytic efficiency at low pollutant
concentrations and complicated separation
after purification. Recently, nanostructured
carbon materials, such as carbon nanotubes
and graphene sheets, offer an exciting
research area owing to their structurally
interesting and unusual properties. TiO2
nanotube (TNT) also is considered as a
modified structure in photo-catalysis owing to
its special electronic and mechanical
properties, high photocatalytic activity, large
specific surface area and high pore volume. In
the present work TNTs were prepared via
hydrothermal method from commercial TiO2
and GO in basic environment followed by acid
washing that encourages nanotube formation.
After calcination the prepared powder were
used in photodegradation experiments to
degrade pharmaceuticals.
1gr P25 +70 ml NaOH 10 M stirring + 0.2 gr GO sonication 30 min
Hydrothermal treatment at 130 ⁰C for 24 hours
Washing with 1 liter HCl 0.1 M until PH 7 reached
Washing with water + drying at 80 ⁰C
Calcinations at 400 ⁰C for 2 hours
Mixing 0.2 gr composite with 1 liter of water containing 100 ppm of pharmaceuticals
Adsorption and photodegradation experiment taking samples regularly, analysis with HPLC
The novel composite exhibited excellent
photocatalytic activity for adsorption- degradation
of pharmaceuticals which is attributed to a thin
two-dimensional sheet support, a large surface
area and a good electron acceptor favoring the
transfer of photo-generated electrons from the
conduction band of TiO2 to the graphene sheet. In
summery adsorption, transparency, conductivity
and very large planar structure of graphene are
the key enhancing factors for photo-degradation
of the pollutants with graphene/ TiO2 composites.
This new composite may find promising
applications in the field of environmental
Photocatalysis specially water purification and it
has the potential to become the ideal substrate
for a number of catalytic and sensing processes.
Fig.3. Electron transfer enhancement by Graphene
Expandable flaked graphite was used as
graphene source and P25 Aeroxide powder as a
TiO2 precursor. In the present work, three simple
strategies have been proposed to synthesize
TNTs on the surfaces of GO: direct mixing of GO
with pre-hydrothermally synthesised TNT powder,
hydrothermal treatment of p25 and GO in high PH
NaOH solution followed by acid washing and
hydrothermal treatment of p25 with GO in natural
aqueous solution. The photo-degradation
experiments were carried out using a 1 litre
cylindrical reactor and an immersion well as
shown in Fig.2. The UV irradiation source was a
125 W mercury lamp. Before the illumination, the
suspension was stirred in the dark for 120 min to
establish the adsorption-desorption equilibrium.
HPLC method was used to measure Famotidine
concentration.
Fig.7. SAD pattern of GO/TNT
Fig.10. SEM image of TNTs/GO composite
synthesised at natural PH
Fig.11. Famotidine UV Photo-degradation
Fig.5. Immersion well
photo-reactor
Fig.1. Importance of photocatalytic remediation
Fig.4
Clean
Environment
Fig.6. TEM image of TNTs
Fig.8. TEM image of GO/TNTs synthesised in
NaoH solution
Fig.9. TEM image of GO/TNTs composite by
mixing
Fig.10. SEM image of GO/TNTs composite in
natural PH