In this work the titanium dioxide powder was prepared by the optimized and simple Sol-Gel method and then characterized. The gelling pH was set to values of 3 (TiO2-A), 7 (TiO2-N) and 9 (TiO2-B) to observe the effect on the properties of the material. In these three cases nanoparticulated materials were obtained with particle sizes between 10nm and 20nm. The larger surface areas were obtained at pH 3, which is several times larger than the others. Furthermore, with the gelling condition pH 3, it was possible to synthesize pure anatase phase titania. Some preliminary results on the test of the photocatalytic activity of the synthesized materials in the reduction of nitric oxide are presented. Based on these results the nanoparticle TiO2, which was prepared in acidic pH 3 with the pure anatase phase and the lowest particle size has the highest reactivity for the photocatalytic reduction of nitric oxide.

TiO₂-coated SiO₂ particles were prepared using
industrially-wasted amorphous SiO₂ particles by an alkoxide method.
The amorphous SiO₂ particles were used as support for TiO₂
photocatalyst. The mean size of the amorphous SiO₂ particle was
approximately 100 nm. The major synthesis parameters were a kind of alcohol
solvent (methanol, ethanol, and 1-propanol) and calcination temperature. The
SiO₂ particles and titanium tetraisopropoxide were mixed in an
alcohol solvent and an appropriate amount of distilled water was added to the
suspension for hydrolysis of the alkoxide. The precipitate was calcined in the
temperature range from 600 to 1300°C to crystallize the deposited
TiO₂. The samples were characterized using XRD, BET and TEM-EDS
analyzer. It was found that the use of SiO₂ support, methanol solvent
in hydrolysis of Ti alkoxide and freeze-drying of product were effective to keep
the anatase phase at high calcination temperature even though the crystallite
size of anatase increased and the specific surface area decreased. As a result,
the maximum decomposition ratio of methylene blue was obtained on the
TiO₂-coated SiO₂ particles synthesized in methanol
solution and calcined at 1000°C.

Bleaching of Congo red catalyzed by ZrO2 nanoparticles was study under UV and sunlight irradiations. The nanoparticles
of ZrO2 have been synthesized by controlled precipitation method. The concentration of ZrOCl2 and ammonia reactants
and the calcinations temperature of ZrO2 were optimized for the control of nanoparticles size. Characterization of
the prepared nanoparticles was studied by using XRD patterns, TEM images and FT-IR spectra. The tetragonal phase of
zirconium oxide was obtained at 550 °C and show the most catalytic effect in dye degradation. The various parameters
such as the irradiation time, amount of nanophotocatalyst, pH of samples, and initial concentration of Congo red were
studied to find desired conditions of photodegradation process. The degradation 98% was achieved at pH 7 catalyzed by
0.7 g/L if ZrO2 nanoparticles in duration time of 125 min. The effect of iso-PrOH, hydrogen peroxide and inorganic anions
was studied on the degradation efficiency of dye. The degradation 98% was obtained in the presence of prepared
nanosized zirconia in comparison with degradation 65% catalyzed by commercially zirconia.

We have carried out the surface modification of photocatalytic TiO₂
with triethoxysilane through dehydrogenation reaction and characterized the
modified photocatalyst by spectroscopic methods, such as FT-IR, solid-state
²⁹Si MAS NMR, XPS, and XRF, etc. We also examined
photocatalytic activity of the immobilized photocatalytic titanium dioxide with
triethoxysilane by decolorization reaction of dyes such as cong red and
methylene blue under visible light. Dispersion test showed that the
photocatalytic titanium dioxide immobilized with triethoxysilane group has kept
higher dispersibility than titanium dioxide itself. No appreciable precipitation
takes place even after standing for 24 h in the 4:6 mixture ratio of ethanol and
water.

Three different studies were
performed for the conversion of water hyacinth (Eichhornia crassipes)
plant into biofuel. In the first study, water hyacinth was saccharified with
diluted sulfuric acid (1% v/v at 110°C for one hour), fermented by yeast
(Saccharomyces cerevisiae). The results showed the formation of
55.20% ethanol and 41.66% acetic acid. In another experiment, water hyacinth was
gasified by using Ni and Co nano catalysts at 50 - 400°C and atmospheric
pressure. In catalytic gasification, CH₄ (2.41 - 6.67%),
C₂H₄ (19.74 - 45.52%), C₃H₄ (21.04 -
45.52%), CH₃OH (1.43 - 24.67%), and C₃H₈ /
CH₃CHO (0.33 - 26.09%) products were obtained. In this
study, anatase form of titanium dioxide photocatalyst was used. The reaction was
performed at room temperature which gives methane, methanol and ethanol. This
study also reports an interesting finding that metal contaminated water hyacinth
could be used for not only the production of biofuel but also
hydrocarbons.

Abstract

Abstract

Abstract

Abstract