الفهرس 
acknowledgmentOnly 14 pages are availabe for public view
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Abstract
The main source of water in Egypt is surface water from the River Nile have been exhausted due to increasing population growth on the one hand, and rapid industrialization and agriculture on the other, Further development measures require review of current water allocations in order to raise efficiencies and protect against pollution, in addition to exploring new options of nonconventional water resources to narrow the gap between water supply and demand . These measures are the pillars of Egypt’s integrated water policy and have been clearly postulated in its National Water Resources Plan 2017.
Photocatalysis plays an important role in dealing with today’s challenging demand for drinking water and waste water treatment technology. Photocatalytic oxidation reactions have the potential to completely mineralize organic compounds to carbon dioxide and water to lead us to a clean and green purification technology for treatment of polluted water. Magnetic photocatalysts provide an alternative solution for the problem of separation of photocatalyst.
This work involves two directions to improve photocatalytic efficiency with economical benefits by different modification methods. One is the preparation of nanosphere and mesoporous TiO2 nanoparticles. Influences of the different preparation parameters on the TiO2 nano powder properties were investigated. Photo/photocatalytic oxidation of (2.6 dichlorophenol- indophenol ) DCPIP, was investigated to determine the optimal operating conditions for degradation in water. Crystallinity, UV irradiation, concentration of pollutant , pH , TiO2 loading.
The other, a magnetic photocatalyst was prepared by coating of CoFe2O4 as magnetic core with an insulating silicon dioxide (SiO2) layer and photocatalytic properties of the outer titanium dioxide shell. Photocatalytic degradation of DCPIP dye by magnetic pahotocatalysis under UV and visible was investigated.
TiO2 with regular shaped spherical nanoparticles was successfully prepared by sol-gel hydrothermal method with basic condition with Teflon autoclave. The characterization results showed that high percentage of anatase phase, decrease in surface area and low porosity.
It is was found that Changes in the microstructural characteristics of as synthesized nanosphere titania as a result of calcination. With increasing calcination temperature beyond 750 0C the crystal size, grain growth, rapid increase in the rutile content and agglomeration and reduction in the surface area were observed.
from the study , it was found that TiO2 as prepared with basic condition at pH = 10 showed that in case of Teflon lined stainless steel was obtain pure anatase phase , less crystal size in comparison to Teflon pressure autoclave.
It is found that a highly active mesoporous TiO2 nanoparticles with anatase phase , 6 nm average crystallite size and high specific surface area 280.7 m2/g has been successfully synthesized via sol-gel/hydrothermal route with acidic condition with Teflon lined stainless steel autoclave .
A highly active mesoporous titania nanoparticles is the most effectiveness for the degradation of DCPIP dye . No obvious degradation of DCPIP was found in the absence of TiO2 and during the irradiation with UVC radiation only, demonstrating the effects of photolysis.
Experimental results showed that the photocatalytic degradation of DCPIP using titania nano particle irradiated by UV light follow Langmuir –Hinshelwood (L-H) kinetic model with reaction rate are mostly of first order and the rate constants decrease with an increase in the initial concentration of DCPIP, but increase with decrease pH. The reaction rate constants also increased with larger TiO2 loading and reached a plateau at TiO2 concentration of 1 g L-1
The optimum photodegradation of DCPIP dye are 1g/L mesoporous TiO2 , pH=3 , 1x10-4 M of solute of DCPIP dye under UV illumination better photocatalytic activity than Degussa P-25 with degradation 96.4 % .
Core-Shell-Shell ( TiO2 / SiO2 /CoFe2O4 ) was successfully prepared by coating of CoFe2O4 as magnetic core with an insulating silicon dioxide (SiO2) layer and photocatalytic properties of the outer titanium dioxide shell to solve problem of separation of photocatalyst and Visible range .
CoFe2O4 LDHs nanoparticles with spinel structure was synthesized by Co-precipitation Method under basic condition at pH = 7 at calcined at 900 0C for 2hrs with superparamagnetic properties, high coercivity and great physical and chemical stability. The crystallization, saturation magnetization , corecivity and remenant magnetization increased with increasing calcinations temperatures.
Silica coated cobalt ferrite nanocomposite was successfully prepared by stober method to produce passive layer between titania and cobalt ferrite and prevent dissolution of iron and electron –hole recombination. TMOS will hydrolyze very rapidly but in doing so will produce toxic methanol and is time limited in the condensation step. TEOS hydrolyzes slower but produces ethanol which is less toxic than methanol to the face and lungs so is often the precursor of choice.
The decreased magnetization values of supported silica are mainly due to the contribution of the volume of the non magnetic coating layer to the total sample volume. It is noted that the non magnetic coating layer can be considered as a magnetically dead layer over the surface of CoFe2O4 particles.
Anatase titania coated silica coated cobalt ferrite nanocomposite was successfully prepared by hydrolysis and condensation of Titanium isopropoxide as precursor with crystal size 5.9 nm . The low values of corecivity and remenant magnetization which are close to zero indicate that the prepared samples exhibited superparamagnetic behaviors at room temperature.
The photodegradation rates of these photocatalysts obey the following order:
4C >P25 > TSC > TSC-300 > CoFe2O4> UV alone . ( UV)
4C > TSC> P25> TSC-300 > CoFe2O4> visible alone . ( Visible)
from this study, it was found that UV/ prepared TiO2(4C) is the most effective catalytic system for degradation of DCPIP dye and can be applied for a wide range of organic compounds.