Sharif Digital Repository

Quantum yield relations were extended by adding effective conditional parameters in photodegradation of organic pollutants such as intensity of light, wavelength of light, average distance from light source, concentrations of dye/pollutant and photocatalyst, and volume of reactor. The geometry of light source and thin film and particulate photocatalytic systems were considered in analysis. Extended quantum yield that is a dimensionless factor is applicable in various types of dye and photocatalyst. This extended quantum yield allowed us to classify photodegradation as reported by scientific groups, performed in various operational conditions in order to identify the degree of similarity... 

The degradation of methyl tert-butyl ether (MTBE) was investigated in the aqueous solution of coated ZnO onto magnetite nanoparticale based on an advanced photocatalytic oxidation process. The photocatalysts were synthesized by coating of ZnO onto magnetite using precipitation method. The sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibration sample magnetometer (VSM). Besides, specific surface area was also determined by BET method. The four effective factors including pH of the reaction mixture, Fe3O4/ZnO magnetic nanoparticles concentration, initial MTBE concentration and molar ratio of [H2O2]/ [MTBE] were optimized using response surface... 

TiO 2 and Pd-modified TiO 2 photocatalysts were prepared by sol-gel method. X-ray diffraction (XRD) data showed that the presence of Pd in TiO 2 catalyst decreases the crystalline size of TiO 2 and stabilizes anatase phase. The study of the photocatalytic activity of the films via Linear Sweep Voltametry (LSV) plots and antibacterial test against Escherichia coli ATCC 25922-a gram negative bacterium-showed that Pd increases the photocatalytic activity of the coatings. Besides, the sequence of layer deposition (TiO 2 and Pd-modified TiO 2) influences the photocatalytic properties. In other words, more photocatalytic activity is obtained when Pd-modified layer is deposited first  

A new dimensionless parameter, Sh-factor, is introduced by using dimensional analysis and extending the quantum yield definition to show power-law relations among light intensity, light wavelength, distance from light source, concentrations of dye/pollutant and photocatalyst, time, and degradation percent. The Sh-factor has the same equation form for photoactivated remediation systems with particulate and thin-film photocatalysts, and it provides mathematical tools to predict degradation performance of a photocatalytic system. These power-law equations separate simply the operational parameters related to the lamp from semiconductor photocatalyst characteristics. The light scattering and... 

In typical photocatalytic processes slurry reactors are used in which catalyst particles have to be separated from the solution after the process ends which means much higher time and costs. Hence, immobilizing process is carried out on the catalyst to overcome this problem. In this work, fiber and network geometries were produced by particle precipitation on substrates. The obtained structures were characterized by XRD, SEM, and Brunauer–Emmett–Teller analyses. Photocatalytic performance of the samples was investigated by methyl orange degradation and also by hydrogen generation from water/methanol splitting. From the SEM images, the size range of the TiO2 particles in the network... 

This study describes the synthesis of TiO2/WO3 composite systems with a varying concentration of WO3 by a glucose-template assisted method and demonstrates their round-the-clock photoactivity performance towards the degradation of methanol (MeOH) under illumination and dark conditions. XRD results indicated a biphasic anatase-rutile nature of TiO2, with tunable concentrations with respect to the WO3 loading. WO3 incorporation extended the light absorption of the system towards visible light, increasing the observed photoactivity. The obtained results were further validated using photo-electrochemical investigations such as photocurrent measurements and the impedance response of the systems.... 

Titania was deposited on glass fibers with a partial epoxy layer coating from a solution containing TiO2 nanoparticles at T = 90°C, and the adsorption process was examined by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared (FT-IR) spectroscopy, and photocatalytic activity measurements. XPS data demonstrated that about 25% of the surface was covered with TiO2 nanoparticles, with 10% on the epoxy layer and 15% on the glass body. It was found that TiO2 nanoparticles can be readily adsorbed on epoxy groups, whereas they have a low tendency to adsorb on carbon polymer chains. This difference can be... 

The development of graphene-based nanocomposites is currently the issue of enormous research interest. Recent advancements have exhibited that semiconductor/graphene nanocomposites can be purposed as a promising new category of catalysts for the heterogeneous photocatalytic treatment of wastewaters. Since semiconductor/graphene nanocomposites have been found efficient in degradation of organic pollutants, photodegradation of phenol and phenolic compounds as hazardous contaminants in aqueous solution has been most widely investigated by these aforementioned nanocomposites. In the present review, after introduction on the properties and the different synthesis methods of semiconductor/graphene... 

Quantum dots (QDs) with unique properties have been widely employed for energy, environmental, and health care applications. Green natural resources, because of their renewability, sustainability, abundance, low cost, and environmental-friendliness, can be utilized for the synthesis of diverse nanoarchitectures. This critical review highlights the recent advancements in the greener and sustainable synthesis of carbon, graphene and metal-based QDs, as well as their significant environmental applications such as photocatalytic hydrogen production, degradation of hazardous contaminants/pollutants and reduction of CO2, with emphasis on the important challenges and future perspectives. © The...