Download or read book Synthesis and Characterization of Undoped and Ag Doped TiO2 ZnO and ZnS Nanoparticles for the Photocatalytic Degradation of 2 chlorophenol Under UV Irradiation written by and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phenol, 2-chlorophenol (2-CP) is used in the manufacture of several chemical compounds including other chlorophenols, dyes, dentifrice and pesticides. The usage of these chemicals results in the discharge of 2-CP that is harmful to most biota in the environment. Therefore there is need to remove or degrade 2-CP from the environment, especially in water.
Download or read book Synthesis and Characterization of Undoped and Doped ZnO Nanoparticles Prepared by Sol gel Process written by Abdub Guyo Ali and published by . This book was released on 2009 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis and Characterization of Nitrogen doped Titanium Oxide Nanoparticles for Visible light Photocatalytic Wastewater Treatment written by Mohammad Ali Pelaschi and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: TiO2 nanoparticles are one of the most suitable materials for photocatalysis, specifically for water and air treatment and removal of a wide variety of organic pollutants such as dyes, aromatic compounds, and chlorinated aromatic compounds. Methods of synthesis of TiO2 are generally categorized in two main classes of wet chemical, and dry methods. Wet chemical methods generally provide a better control over size, size distribution, and shape; all of which significantly affect photocatalytic performance of the produced nanoparticles. Despite its advantages over other semiconductor photocatalysts, wide band-gap of titania restrains its photocatalytic activity to only UV light, which only makes up to 5% of the light reaching surface of the earth. To induce visible-light activity, titania has been doped by different dopants, including transition metal-dopants such as Fe, and Co and non-metal dopants such as N, and C. Nitrogen has been shown to be a better dopant, providing a suitably placed energy state within the band-gap of TiO2, and not suffering from issues related to transition-metal dopants such as low thermal and physical stability and high electron-hole recombination rates. To dope titania with nitrogen, one could add the nitrogen source together with other precursors during synthesis, referred to as wet chemical doping methods, or anneal the synthesized titania nanoparticles under a flow of ammonia at high temperatures, referred to as dry doping methods. While different doping methods have been studied individually, the author maintains that there has been an absence of research comparing the effectiveness of these methods, on photocatalytic performance of N-doped TiO2 within a consistent experiment. In this research TiO2 nanoparticles were synthesized by a facile, inexpensive sol-gel method, and doping was done by wet chemical methods, dry methods, and a combination of both these methods. Visible-light photocatalytic activity of these nanoparticles was evaluated by their efficiency in degradation of methyl orange. The results show wet doping methods increase the efficiency of titania nanoparticles more than dry doping, or combination of both. Further investigation showed that the main reason for higher activity of wet chemically doped nanoparticles is due to their higher available surface area of 131.7 m2.g-1. After normalizing the available surface area, measured by the BET method, it was shown that a combination of wet chemical doping, and dry doping at 600 °C result in the most active nanoparticles, but high temperature dry doping severely decreases the surface area, lowering the overall efficiency of the product. Additionally, N-doped TiO2 nanoparticles were synthesized using a simple hydrothermal method, in which the nitrogen source was used not only to dope, but also to control shape, size, size distribution, and morphology of the titania nanoparticles, and to induce aqueous colloidal stability. It was shown that addition of triethylamine during the synthesis, results in ultra-small, colloidally stable, cubic TiO2 nanoparticles, while using triethanolamine results in formation of TiO2 pallets, assembled into spherical, rose-like structures. The synthesized nanoparticles show impressive efficiency in visible-light removal of phenol, 4-chlorophenol, and pentachlorophenol, achieving 100% degradation of a 100-ppm phenol solution in 90 min, more than 98% degradation of a 20-ppm 4-chlorophenol solution in 90 min, and 97% degradation of a 10-ppm pentachlorophenol in 180 min with 500 ppm loading of the catalyst in all cases. Moreover, synthesized nanoparticles showed no sign of deactivation after 5 consecutive runs, removing 4-chlorophenol, showing their reusability.
Download or read book Chemical Vapor Synthesis and Characterization of Undoped Doped and Functionalized ZnO Nanoparticles written by Moazzam Ali and published by . This book was released on 2010 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photocatalytic Activity Enhancement of Titanium Dioxide Nanoparticles written by Mohamed A. Barakat and published by Springer. This book was released on 2015-10-26 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this brief, a comprehensive review of the UV/visible-TiO2 photocatalytic oxidation process is presented with an insight into the mechanisms involved, the role of titanium dioxide as a catalyst, irradiation sources, types of reactors, and a comparison between various modes of TiO2 application. An overview of the development and enhancement of the activity of TiO2 nanoparticles in photocatalysis is presented. The topics covered include a detailed look at the unique properties of the TiO2 nanoparticles and their relationship to photocatalytic properties. The utilization of the TiO2 nanoparticles as photocatalysts, in the non-doped and doped forms is also reviewed. Finally, the use of modified TiO2 nanoparticles has made a significant contribution in providing definitive mechanistic information regarding the visible light photocatalytic processes.
Download or read book ZnO and TiO2 Based Nanostructures written by Andrea Lamberti and published by MDPI. This book was released on 2018-10-15 with total page 381 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a printed edition of the Special Issue "ZnO and TiO2 Based Nanostructures" that was published in Nanomaterials
Download or read book Synthesis of Zinc Oxide by Sol Gel Method for Photoelectrochemical Cells written by Siti Salwa Alias and published by Springer Science & Business Media. This book was released on 2013-11-20 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the study of synthesized ZnO powder using Zn(CH3COO)2∙2H2O precursor, methanol (as solvent), and sodium hydroxide (NaOH) to vary the pH. The successfully synthesized ZnO powder from the sol-gel centrifugation and sol-gel storage methods were characterized and investigated by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, UV–visible spectroscopy, and photoluminescence test to compare the properties of the nanoparticles. The best characteristic of the ZnO powder from both methods was observed when the powders were coated on an ITO glass to fabricate a PEC. The current density–voltage performances of both PECs were investigated under luminescent and dark conditions.
Download or read book Green Photocatalytic Semiconductors written by Seema Garg and published by Springer Nature. This book was released on 2021-09-20 with total page 855 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book comprises a detailed overview on the role of photocatalysts for environmental remediation, hydrogen production and carbon dioxide reduction. Effective ways to enhance the photocatalytic activity of the material via doping, hybrid material, laser light and nanocomposites have been discussed in this book. The book also further elaborates the role of metal nanoparticles, rare earth doping, sensitizers, surface oxygen vacancy, interface engineering and band gap engineering for enhancing the photocatalytic activity. An approach to recover the photocatalytic material via immobilization is also presented. This book brings to light much of the recent research in the development of such semiconductor photocatalytic systems. The book will thus be of relevance to researchers in the field of: material science, environmental science & technology, photocatalytic applications, newer methods of energy generation & conversion and industrial applications.
Download or read book Characterisation of Semi conductor Zinc Oxide ZnO Thin Films as Photocatalysts written by Arshid Mahmood Ali and published by . This book was released on 2011 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this project was to study the suitability of nanostructured ZnO thin films as efficient photocatalysts and to characterise any issues that may be involved in the scale-up of photocatalytic systems based on these types of immobilised nanostructure ZnO thin films. In particular, this study involved fabricating and then evaluating the effectiveness of a range of nanostructured zinc oxide (ZnO) thin films with different structures and chemistries (i.e. undoped and doped) as photocatalysts, and thereafter to systematically relate: the initial and reacted surface morphology; photocatalytic activity in terms of reaction rate; reaction intermediates and products; and liquid phase and solid phase reaction mechanisms under both limited and rich oxygen conditions at two different UV irradiation wavelengths (254nm and 340nm). These nanostructured thin films (i.e. undoped ZnO; nitrogen doped ZnO - N:ZnO; cobalt doped ZnO - Co:ZnO) were produced using an innovative combination of magnetron sputtered surfaces and hydrothermal solution deposition that allows the morphology, porosity and thickness to be controlled by varying the composition and processing conditions. SEM, UV-Vis, HPLC, LC-MS, AAS and XRD were used to study the changes in thin film morphology, Methylene Blue (MB) degradation and its reaction intermediates, the presence of Zn metal in the reaction fluid, if any, and crystallinity before and after the photocatalytic reaction respectively. Undoped ZnO thin films: Results showed a clear relationship between surface morphology (and the related thin film preparation method) and photocatalytic activity for the ZnO thin film supported catalysts: the tallest, most aligned structure had the highest photocatalytic activity, whilst the smallest, least aligned structure had the lowest. Thus, the MB degradation rate was the fastest for the ZnO thin film (S2-MS) with a uniform arrayed structure. Adding oxygen made the films more stable: in oxygen-limited conditions, SEM and atomic absorption spectroscopy indicated zinc leaching had occurred. Furthermore, with additional oxygen the zinc leaching was minimised under the same reaction conditions. It is thought that this additional oxygen is either minimising the release of, or replacing lost ZnO lattice oxygens, indicating that this ZnO photocatalytic oxidation could be occurring via a Mars van Krevelen type redox mechanism. There was also a significant difference in MB degradation rates, as well as reaction intermediate formation and destruction rates, correlated to the morphologies and crystallinity at both UV wavelengths, with the highest reaction rates at 340nm. Reaction analysis indicates that there is a competition between two different photocatalytic mechanisms: conventional photocatalysed radical oxidation and lattice oxygen-driven oxidation. The dominant reaction mechanism depends on the thin film morphology, crystallinity, availability of oxidant and the wavelength of the incident UV. The surface-photocatalysed radical formation was predominant for more aligned, highly crystalline, morphologies, where there was plentiful oxygen and UV irradiation at 340nm. Lattice oxygen photodegradation was predominant for the less aligned, more amorphous morphologies and UV irradiation at 254nm. Doped (Co:ZnO) thin films: Results showed that cobalt dopant increases the photo-stability of the corresponding undoped thin films under oxygen-limited conditions - increasing with the increased dopant concentration. This increased stability of Co:ZnO nanostructure thin films comes with a price, however: the photocatalytic activity and concomitant degradation of MB and its azo dyes reaction intermediates is in general lowered, compared to the undoped ZnO thin films. At higher dopant concentrations, under oxygen-rich conditions and with UV irradiation at 254nm and 340nm, the MB degradation most likely occurs via a conventional photocatalytic reaction mechanism and/or via charge transfer of the MB into Azure B (AB) with the absence of Mars van Krevelen type mechanism (because of the increased lattice stability). At lower dopant concentrations under oxygen-limited conditions with UV irradiation at 254nm and 340nm, the Mars van Krevelen type reaction mechanism is probably the main mechanism propagating the oxidation of MB. Overall, the undoped morphologies were more photocatalytically active compared to the doped morphologies. In general, this work has shown that several different solid and liquid phase photocatalytic reaction mechanisms govern the photocatalytic degradation of azo dyes such as MB on nanostructured ZnO thin films, and that surface morphology, crystallinity, lack or presence of oxygen, and the dopant concentration are the key parameters governing the overall photocatalytic activity and the activation of these different solid and liquid photocatalytic reaction mechanisms.
Download or read book Zinc Oxide and Manganese Doped Zinc Oxide Nanoparticles written by Yadollah Abdollahi and published by LAP Lambert Academic Publishing. This book was released on 2012-06 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book consists of synthesis and characterization of ZnO and Mn-doped ZnO nanoparticles for photocatalyst process. The work contains synthesis (co- precipitation), Characterization (TEM, SEM, EDX, FTIR, XRD, BET, UV-visible NIR) and application of ZnO and Mn-doped ZnO nanoparticles. The application included photodegradation of m-, o- and p-cresol that was carried out under UV and visible irradiation at room temperature, atmospheric pressure, and different PH by batch photoreactors. The intermediates were identified by UPLC and mineralization was confirmed by TOC measurement. As a result, 1%wt Mn-doped ZnO with lower particles size, higher surface area, high cresols adsorption, lower agglomerate, appropriate band gap and higher photodegradation ability than other % of Mn-doped ZnO is the best photocatalyst that may enhance the photocatalyst activity of ZnO under visible light. "
Download or read book Preparation Properties and Photocatalytic Activity of Doped and Undoped Metal Oxide Nanomaterials written by Azad Kumar and published by BFC Publications. This book was released on 2021-07-10 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, describes a proficient method for synthesis of Titania, titania based nanocomposites, Ni:TiO2, Co:Ni:TiO2, Co:La:TiO2, Co:TiO2, Cu-TiO2, TiO2/PAni, TiO2/PAni/GO, TiO2/PPy and TiO2/PPy/GO nanocomposites. The doping of metal ions were made by solution impregnation method in the Titania nanopowder followed by the calcination in the muffle furnace. The polymer based nanocomposites were prepared by one-step in situ deposition oxidative polymerization of Aniline and pyrrole hydrochloride using Ammonium persulphate (APS) as an oxidant in the presence of ultra-fine grade powder of TiO2 nanoparticles cooled in an ice bath. The obtained nanocomposites were characterized by XRD, TEM, SEM and UV-Vis for band gap determination. The Photocatalytic degradation of Eriochrome black-T, Acetic acid, methyl blue, methyl green, Thymol Blue, Rose Bengal and Victoria blue dye was done at different condition viz concentration of dye, time of illumination, pH and dose of the photocatalyst. The maximum photodegradation was found at 7 pH, lowest concentration of compound solution, highest amount of photocatalyst and 120 min irradiation of visible light. Kinetics of photodegradation was investigated for organic dyes were found first order kinetics. The doping of metal ions and coating of Polyaniline and PolyPyrrole and GO has enhanced the photocatalytic activity of Titania.
Download or read book Photocatalytic Semiconductors written by Aracely Hernández-Ramírez and published by Springer. This book was released on 2014-11-17 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: This critical volume examines the different methods used for the synthesis of a great number of photocatalysts, including TiO2, ZnO and other modified semiconductors, as well as characterization techniques used for determining the optical, structural and morphological properties of the semiconducting materials. Additionally, the authors discuss photoelectrochemical methods for determining the light activity of the photocatalytic semiconductors by means of measurement of properties such as band gap energy, flat band potential and kinetics of hole and electron transfer. Photocatalytic Semiconductors: Synthesis, Characterization and Environmental Applications provide an overview of the semiconductor materials from first- to third-generation photocatalysts and their applications in wastewater treatment and water disinfection. The book further presents economic and toxicological aspects in the production and application of photocatalytic materials.
Download or read book Synthesis of TiO2 based nanoparticles for photocatalytic applications written by Kranthi Kumar Akurati and published by Cuvillier Verlag. This book was released on 2008-10-27 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: Various gas phase synthesis routes have been employed to produce TiO2 based nanoparticles for photocatalytic applications. Synthesis routes have been selected depending up on the feasibility/constraints of the particular process to produce a given kind of material. The first attempt at producing the photocatalysts involved the synthesis of pure TiO2 nanoparticles by a flame aerosol process. The growth behaviour of TiO2 particles which has significant influence on their crystallinity and surface area, has been controlled by varying the process parameters and selecting suitable flame configurations. An existing method to determine the crystallinity of the powder has been modified which facilitates comparison of the degree of crystallinity of the nanoparticles synthesized by various methods. Resultant TiO2 nanoparticles were characterized by X-ray diffraction (XRD) and nitrogen physisorption to determine the degree of crystallinity quantitatively and surface area, respectively, and the decomposition rate of an industrial dye, methylene blue, has been taken as the measure of the photocatalytic activity (PCA). The importance of an optimum combination of crystallinity and surface area for improved PCA has been shown by comparing the PCA of the as-synthesized nanoparticles with commercial TiO2 (Degussa P25). By depositing another semiconductor material on TiO2, PCA of the resultant composite photocatalyst can be improved due to the effective separation of the charge carriers. The deposited semiconductor has been chosen by virtue of its conduction band potential which should be higher than that of the TiO2. Accordingly, SnO2/TiO2 composite nanoparticles have been synthesized in a single-step by feeding evaporated precursor mixtures into an atmospheric pressure diffusion flame. For the lowest concentration (3.4 mol %) of SnO2 employed in this study anatase phase of TiO2 is stabilized, while segregation of SnO2 is seen at medium (6.9 to 12.4 mol %) and high concentrations (20.3 mol %). Though the equilibrium phase diagram predicts complete solubility of one oxide in another at all compositions, segregation of SnO2 phase is observed which is explained by the usage of diffusion flame in the present study. A particle formation mechanism of SnO2/TiO2 composites is proposed based on the single component aerosol formation. Photocatalytic activity of the composite particles is tested for the degradation of methylene blue and is compared with pure TiO2 synthesized under similar conditions. Improved photocatalytic activity of the composite particles is attributed to the stabilized anatase phase and better charge separation due to the coupling of TiO2 and SnO2 within the composite nanoparticles. The adsorption properties of the SnO2/TiO2 particles are similar to the pure TiO2 particles and the PCA can be further improved coupling the advantages of adsorption properties and charge carrier separation in a single system. WO3 is the kind of semiconductor material that has suitable conduction band potential and surface acidity to perform the dual function mentioned above. Due to the non-availability of the suitable volatile precursor for WO3, WO3/TiO2 composite nanoparticles have been synthesized by using flame spray synthesis. W and Ti precursors were dissolved in a suitable solvent and sprayed into the high temperature acetylene flame using an atomizing gas. Particles with controlled W:Ti ratios were produced at various flow rates of precursor solution and the resulting powders were characterized by BET (Brunauer-Emmett-Teller) surface area analysis, XRD, TEM (Transmission electron microscopy), Raman and ATR-IR (Attenuated total reflection infrared) spectroscopy. Two-dimensional coordinatively unsaturated wolframyl species were well dispersed on the TiO2 surface for the samples equal to or less than 3.6 mol% WO3 and contributed to increase the surface acidity. Crystalline WO3 was formed for the samples above 3.6 mol% WO3. The formation of crystalline WO3 is attributed to the enhanced rate of condensation of W species with increasing loading of tungsten. The variation of lambda (defined as the ratio of the actual oxygen-to-fuel ratio of the reactants to the stoichiometric fuel-to-oxygen ratio) affects the type of surface species dispersed on TiO2 particles and thereby the resultant acidity. The improved photocatalytic activity of the composite particles is attributed to the increased surface acidity and better charge separation due to the coupling of WOx species and TiO2 within the composite nanoparticles. The development of a practical photocatalytic system focuses on the cost effectiveness of the process. The usage of the expensive solar concentrators and artificial ultraviolet (UV) irradiation for photocatalytic reactions has negative influences on the cost effectiveness. In addition to the cost effectiveness resulting from using solar energy, abundance of the visible light (55 % compared to 6 % of UV) motivates to synthesize TiO2 nanoparticles that absorb visible light. Nitrogen doped TiO2 nanoparticles that absorbs visible light have been synthesized by hot-wall reactor synthesis. The extent of doping of nitrogen is controlled by varying the hot-wall reactor temperature and the flow rate of the gaseous reactants. Increasing the nitrogen concentration above a certain value reduces the PCA and is attributed to the formation of Ti3+ that act as recombination centre for the charge carriers. The concentration of nitrogen at which significant Ti3+ formation takes place has been systematically investigated by XPS (X-ray photoelectron spectroscopy) measurements.
Download or read book Synthesis and Characterization of Carbon Coated and Nitrogen Doped TiO2 for Enhanced Photocatalytic Degradation of Organic Pollutants Under Uv vis and Visible Ligth Irradiation written by Wan Izhan Nawawi Wan Ismail and published by . This book was released on 2013 with total page 466 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Green Synthesis and Characterization of ZnO Nanoparticles for Photocatalytic Degradation of Anthracene written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Heterogeneous Photocatalysis Using Inorganic Semiconductor Solids written by Umar Ibrahim Gaya and published by Springer Science & Business Media. This book was released on 2013-11-08 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book underscores the essential principles of photocatalysis and provides an update on its scientific foundations, research advances, and current opinions, and interpretations. It consists of an introduction to the concepts that form the backbone of photocatalysis, from the principles of solid-state chemistry and physics to the role of reactive oxidizing species. Having recognised the organic link with chemical kinetics, part of the book describes kinetic concepts as they apply to photocatalysis. The dependence of rate on the reaction conditions and parameters is detailed, the retrospective and prospective aspects of the mechanism of photocatalysis are highlighted, and the adsorption models, photocatalytic rate expressions, and kinetic disguises are examined. This book also discusses the structure, property, and activity relationship of prototypical semiconductor photocatalysts and reviews how to extend their spectral absorption to the visible region to enable the effective use of visible solar spectrum. Lastly, it presents strategies for deriving substantially improved photoactivity from semiconductor materials to support the latest applications and potential trends.
Download or read book Optical Properties of Mixed Crystals written by R.J. Elliott and published by Elsevier. This book was released on 2012-12-02 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt: ``Optical Properties of Mixed Crystals'' is concerned with the description of optical processes in substitutionally disordered semiconductors and insulators which can be basically described through their elementary excitations. Two of the chapters relate to the phonon response including the effect of side bands on electron transitions. Two relate to electronic spectra, one on photoelectron spectroscopy and the other on excitons. A further chapter deals with magnons in magnetic crystals and a final chapter is related to fluctuations and band edge effects.Each chapter deals with a specific class of excitation, but the book makes it clear that the fundamental structure of the excitation spectra, including band formation, band tailing and localisation is common to every type of excitation. The volume shows how some basic concepts and ideas can be widely applied to bring coherence and understanding to a diverse area of solid state physics. It therefore provides an up-to-date summary of the experimental and theoretical situation in an important and rapidly developing field and brings together for the first time a discussion of the many different types of spectra which appear in mixed crystals.
