Sawsan A. Mahmoud

Sol-Gel and Thermally Evaporated Nanostructured Thin ZnO Films for Photocatalytic Degradation of Trichlorophenol

In the present work, thermal evaporation and sol–gel coating techniques were applied to fabricate nanostructured thin ZnO films. The phase structure and surface morphology of the obtained films were investigated by X-ray diffractometer (XRD) and scanning electron microscope (SEM), respectively. The topography and 2D profile of the thin ZnO films prepared by both techniques were studied by optical profiler. The results revealed that the thermally evaporated thin film has a comparatively smoother surface of hexagonal wurtzite structure with grain size 12 nm and 51 m2/g. On the other hand, sol–gel films exhibited rough surface with a strong preferred orientation of 25 nm grain size and 27 m2/g surface area. Following deposition process, the obtained films were applied for the photodegradation of 2,4,6-trichlorophenol (TCP) in water in presence of UV irradiation. The concentrations of TCP and its intermediates produced in the solution during the photodegradation were determined by high performance liquid chromatography (HPLC) at defined irradiation times. Complete decay of TCP and its intermediates was observed after 60 min when the thermal evaporated photocatalyst was applied. However, by operating sol–gel catalyst, the concentration of intermediates initially increased and then remained constant with irradiation time. Although the degradation of TCP followed first-order kinetic for both catalysts, higher photocatalytic activity was exhibited by the thermally evaporated ZnO thin film in comparison with sol–gel one.

Photolysis and Photocatalysis of 1,4 Dichlorobenzene Using Sputtered TiO2 Thin Films

The rate of 1,4-dichlorobenzene (1,4-DCB) degradation in the aqueous phase was investigated under direct photolysis or photocatalysis in the presence of TiO2 thin film prepared by reactive sputtering using a metal Ti target and a reaction sputtering atmosphere of argon and oxygen. The prepared thin films were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). XPS confirmed the presence of completely oxidized TiO2 films whereas XRD showed that the films contained a mixture of rutile and anatase phases with rutile being approximately 30% of the total volume. Two lamps, both of the same power but different wavelength range were employed as irradiation sources. Photocatalysis showed faster removal of 1,4-DCB as compared to direct photolysis. The complete degradation was attained using the freshly prepared TiO2 sample. The intermediate produced during the photocatalysis was benzoquinone. Photolysis using visible irradiation was relatively slower and both benzoquinone and hydroquinone were formed as intermediates. Higher initial degradation rates were observed when the same film was re-used, most probably due to the effect of washing of the TiO2 thin films surface with methanol.

Levels, compositions, and quality of some Egyptian surface sediments from Suez Gulf, as integrated from polycyclic hydrocarbons

ABSTRACT The aim of this study was to investigate the contamination of surface sediments in Suez Gulf, Egypt, by polycyclic aromatic hydrocarbons (PAHs). Total concentrations of 16 PAHs were ranged from 6.6009 to 1770.3265 ng/g sed. dry wet with an average of 398.617 ng/g sed. dry wet, which is relatively high in comparison with other estuaries around the world. Source identification implied that the PAHs were originated mainly from pyrolytic sources. However, source patterns may be continuously changed to a petrogenic origin due to the heavy ship traffic and continuous discharge of oily sewage in this area. The PAH levels were also compared with international Sediments Quality Guidelines and Sediments Quality Criteria, and the results indicated adverse effects for most individual PAHs. However, toxic effects related to acenaphthylene (A); benzo [b] fluoranthene (Bbf); benzo [K] fluoranthene (Bkf); dibenzo [a,h] anthracene (DahA); and benzo [ghi] perylene (Bp) would occur occasionally in most locations in the Gulf.

Assessment of polycyclic aromatic hydrocarbons of organic richness in seawater from some coastal area around Alexandria city, Egypt

ABSTRACT The compositions of polycyclic aromatic hydrocarbons used as chemical markers for the identifying of different sources in the surface seawater of Alexandria coastal area. The quantitative analysis of polycyclic aromatic hydrocarbons (PAHs) showed a concentration ranged from 8970.939-1254756.00 ng/L, which exceed the maximum admissible concentrations of PAHs (200 ng/L) for the water standard of European Union. The calculated diagnostic ratios suggested that the sources of PAHs at the majority of the studied area are derived primarily from pyrogenic sources from incomplete fuel combustion of the boats and vehicle engines with lesser amounts of PAHs contributed from petrogenic sources. Some stations displayed mixed sources in comparison to many other studied marine systems, the PAHs concentrations detected at Alexandria area were considered be higher to pose health risks to aquatic bodies.

Compositions, sources, and ecological risk assessment of poly-aromatic hydrocarbons in surface sediments along the Suez Gulf, Egypt

ABSTRACT Poly-aromatic hydrocarbons (PAHs) were analyzed in sediments collected from the Suez Gulf to evaluate the composition, sources, and ecological risk assessment. The highest concentration of total PAHs is recorded in sediments collected from Inlet of Suez Oil Petroleum Company (SOPC), followed by east of the Outlet of SOPC and Outlet of SOPC. While lower concentrations of total PAHs are detected in Suez Beach west of the Outlet of SOPC, from Inlet of Al-Nasr Petroleum Company (NPC). The ratio of ∑LPAHs/∑HPAHs was <1, revealing their pyrogenic sources. The concentration levels of PAHs in the current study were compared to the effect range low (ERL) and the effect range medium (ERM) values for all investigated stations was below the ERL except for Inlet of SOPC. This finding indicated that PAHs in the surface sediments of the studied area have adverse biological effects, which may cause severe adverse biological and acute effects. The high levels of BaP equivalent (BaPE) values east of the Outlet of SOPC indicate that PAHs have relatively high toxicity among all sites. The toxic equivalent (TEQcarc) values of the sediment samples varied from 0.1883 to 1449.286 ng/g TEQ, with the mean value of 144.295 ng/g TEQ; the higher total TEQcarc values were found at 50 m east of the Outlet of SOPC: 1449.286 ng/g TEQ.

Nanostructured Ti-Fe Thin Layered Photocatalyst via Sol-Gel Technique

The finding of of Zhu et al. [1] that iron-ion-doped TiO2 powders by hydrothermal hydrolysis and crystallization exhibited that the amount of doped iron ion significantly affected the phoyocatalytic degradation activity of XRG yellow dye and Fe optimum content could enhance photocatalytic activity under UV and visible light irradiation has encourage us to carry out this work. Hence, we prepared and examined the photocatalytic activities of a series of TiO2/Fe2O3 mixtures of thin layers of TiO2 and Fe2O3 using the sol-gel method and found that the TiO2(5)/Fe2O3(1) catalyst the most active for anthracene photodegradation. This catalyst acquired the highest surface area, proper pore size distribution and the smaller nano-particle size.Copyright

Nanocrystalline ZnO Thin Film for Photocatalytic Purification of Water

A thin film ZnO nanostructured catalyst exhibited a significantly greater superiority for the photodegradation of 2, 4, 6-TCP in water over photolysis via irradiation with UV of 254 nm wavelength. This ZnO photocatalyst was prepared via Zn metal evaporation and deposition on a glass sheet followed by calcination ature from 350 to 500 °C and the calcination time from 1 to 2h shows via SEM photography a decrease of ZnO nanoparticales sizes sheet followed by calcination (oxidation). Increasing the calcination temperature from 350 to 500 °C and the calcination time from 1 to 2h shows via SEM photography a decrease of ZnO nanoparticales sizes as well as the shape of their crystals finer needles, for which the crystallinity enhances as revealed by XRD. 2, 4, 6-Trichlorophenol was used as a model pollutant in water. Its photolysis using UV only or photocatalysis using UV irradiation in presence of the ZnO thin film catalyst indicated aromatic intermediates, which suffered of Cl by OH, addition of OH in a bare carbon in the aromatic ring, whereas in Photocatalysis deeper oxidation products, e.g., quinones and hydroquinones were also formed.Copyright