الفهرس 
Introduction and Literature ReviewOnly 14 pages are availabe for public view
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Abstract
Water Pollution is one of the most important environmental
issues, as many hazardous micro pollutants, such as heavy metals,
pharmaceuticals, dyes and fertilizers are increasingly being released
into the watercourses. Since these pollutants present high toxicities, it is
essential to develop efficient techniques for water decontamination.
Many processes have been proposed to retard these pollutants.
One of these, semiconductor based heterogeneous
photocatalysis considered one of the most promising techniques for
wastewater treatment.
Titanium dioxide (TiO2) is one of the most powerful
semiconductor photocatalyst that has been widely studied because of its
unique photoelectric properties, high chemical stability, nontoxicity and
low cost. Despite, its role as a good photocatalyst semiconductor
material, its efficiency is limited by its wide band gap and the fast
electron–hole recombination.
Several approaches have been developed to tailor TiO2
’s band
gap and to reduce the electron-hole recombination. One of these
approaches is doping TiO2 with rare earth elements and mixing TiO2
with carbon supports materials as graphene oxide (GO) and carbon
nano tubes (CNT) to develop the photocatalytic activites of TiO2
nanocomposites.In this work of research, we investigated a new photocatalytic
systems that based on Ln3+-doped TiO2/GO and Ln3+-doped
TiO2/GO/CNT systems that have been prepared via a low cost and
environmental friendly hydrothermal methods.
Moreover, the effect of doping with some lanthanide metal ions
such as (Eu3+ and Sm3+) metal ions on the different prepared TiO2/GO
and TiO2/GO/CNT samples has been also addressed in this work.
photocatalytic activity of TiO2, TiO2/GO, Ln3+-doped TiO2/GO
and Ln3+-doped TiO2/GO/CNT has been tested and investigated on the
decolorization and degaradation of some commercial dyes such as
Methylene Blue (MB) and Remazol Red RB 133 (RR) in water under
the UV light and measured the total amount of organic carbon obtained
from the photodegradation of the organic dyes.
The thesis consists of three chapters:
Chapter I gives a general introduction including problematic of
the energy and environmental pollution and the role of nanotechnology
and nano semiconductors photocatalysis in solving such problems. A
theoretical back ground about the TiO2 as a nano semiconductor
photocatalyst is introduced. Furthermore, Different types of doping
materials doped TiO2 nanoparticles and their preparation methods used
in this study have been listed. And finally, the literature review
concerning the thesis topics is also given.Chapter II demonstrates the different experimental techniques and data
analysis methods used in this thesis.
Chapter III includes the results which are divided into two main parts
including discussion of the obtained results and conclusion of each part
which are summarized as follows:
Part I: Preparation and characterization of un-doped and Lndoped
TiO2 supported onto GO and CNTs substrates.
In this part, morphological and crystallographic characterization
have been carried out on Graphene oxide sheets prepared by
modified Hummer method.
Optimization of TiO2 supported on GO sheets at different
weight ratios which are symbolized as TiO2/GO (1:0.02),
(1:0.01), (1:0.007) and (1:0.006) respectively. Moreover, the
effect of doping with some lanthanide metal ions such as (Eu3+
and Sm3+) metal ions on the different prepared TiO2/GO and
TiO2/GO/CNT samples has been also addressed in this part.
The photocatalytic nanomaterials have been characterized by Xray
diffraction (XRD), scanning electron microscopy (SEM)
equipped with Energy dispersive X-ray (EDX), transmission
electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy (RS), Fluorescence
Spectrophotometer and Diffuse Reflection Spectrometer (DRS).
The XRD and Raman analysis of the as-prepared
nanocomposites show they are crystalline and consist of anatase
phase of TiO2 and the calculated crystallite size are decreased
after doping with Ln3+ metal ions and ranged from 6.6 - 4.9 nm.
The SEM and TEM micrographs show the as-prepared
nanocomposites have a small spherical distributed shape. A
good contact and interaction between Ln3+- doped TiO2
nanoparticles supported on GO and CNTs achieved by the
hydrothermal process. These micrographs also show the
presence of TiO2 agglomerates due to the high amount of TiO2
compared with the GO and CNTs.
The UV-Visible absorption spectra show that dopants with Ln3+
metal ions on TiO2 cause an increase in the absorption edge of
TiO2, leading to reduction in bandgap energies of the prepared
nanocomposites.
The optimum concentration of the Ln3+ doped metal ions are
0.015% Sm-TiO2/GO and 0.015% Eu-TiO2/GO.
Part II: Photocatalytic activity of the undoped and Ln3+-doped
TiO2 supported photocatalysts
The photocatalytic activity of the as-prepared samples has been
tested on the degradation of Methylene blue and Remazol red. The rate kinetics of the photocatalytic degradation obeys first
order rate kinetics with respect to the initial dye concentration.
The order of photodegradation efficiency MB dye under UV
light is as follows: TiO2/GO (1:0.01) > (1:0.02) > (1:0.007) >
(1:0.006) > TiO2. This result suggests that the (1:0.01) TiO2/GO
nanocomposite is more efficient than pure TiO2 for MB
degradation.
The photocatalytic activity of all Ln3+–TiO2/GO catalysts
achieved higher rates of MB degradation than the pure TiO2 and
TiO2/GO catalysts.
The enhancement of MB photodegradation rate increased with
the increase of Ln3+ content concentration, but declined while
the Ln3+ content reached a higher level. The rate constant of the
MB photodegradation of 0.015 mol% Eu-TiO2/GO is higher
than that of 0.015 mol% Sm-TiO2/GO.
The addition of CNTs also enhance the photocatalytic
degradation of MB dye under UV light is as follows:
TiO2/GO/CNT 7.5% > 5% > 2.5% > 10% > TiO2/GO (1:0.01) >
TiO2.
The mineralization of MB and RR dyes is investigated using the
photocatalyst (0.015% Eu-TiO2/GO) in return of COD where,
99.9% and 91% COD removal from MB and RR, respectively
have been achieved under UV-A home-made reactor for 90 and
180 min, respectively.Moreover, an English as well as Arabic summaries are represented.
The references are also cited.