Aspects of the Heterogeneous Photocatalytic Degradation of Organic Pollutants in Water PDF Download
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Author: Laurence Timothy Hogg
Publisher:
ISBN:
Category :
Languages : en
Pages : 151
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Book Description
The photo-activity and specific surface area of a number of potentially-useful photocatalysts has been determined using the liquid phase dehydrogenation of propan-2-ol (activity), and the adsorption of argon gas at 77K (surface area). Degussa P25 titanium dioxide was considered the most active solid on this basis (activity=l23_+5xl0-4mol.g-1h-1, SA 39_+3 m2g-1). The photo-activity of suspended solids was found to be dependent upon the anatase:rutile ratio and the catalyst concentration, but relatively independent of the surface area for structurally different specimens. This has been explained in terms of the absorbance of band-gap radiation by the solid as a function of suspended particulate mass. Experimental evidence regarding the rate of propan-2-ol photo-oxidation under oxygen-purged conditions compared to the observed rate under air, suggests a rate dependence upon the partial pressure of oxygen of P02 1/2 The total photocatalytic mineralisation of aqueous 2-chlorophenol mediated by Degussa P25 TiO2 has been achieved in approximately 5 hours (c0 2CP = 5x10-4M), with an initial zero order rate constant of 1.7x10-4mol.g-1h-1. (6h irradiation period). The kinetics of the reaction are shown to be loosely expressed by the Langmuir-Hinshelwood kinetic model, but complex kinetics were in evidence under conditions of partial mineralisation, which may be dictated by the solution pH and/or the concentration of intermediate degradation products. A mechanism for the photo-oxidation reaction has also been proposed, based upon experimental evidence involving measurements of pH, conductance, carbon dioxide evolution and GCMS studies, which suggests a complex reaction pathway. The photocatalytic mineralisation of a saturated solution of gamma - hexachlorocyclohexane (Lindane, 7ppm), has been achieved in approximately 2 hours by this method and the mechanistic and kinetic details of this reaction are discussed briefly.
Author: Laurence Timothy Hogg
Publisher:
ISBN:
Category :
Languages : en
Pages : 151
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Book Description
The photo-activity and specific surface area of a number of potentially-useful photocatalysts has been determined using the liquid phase dehydrogenation of propan-2-ol (activity), and the adsorption of argon gas at 77K (surface area). Degussa P25 titanium dioxide was considered the most active solid on this basis (activity=l23_+5xl0-4mol.g-1h-1, SA 39_+3 m2g-1). The photo-activity of suspended solids was found to be dependent upon the anatase:rutile ratio and the catalyst concentration, but relatively independent of the surface area for structurally different specimens. This has been explained in terms of the absorbance of band-gap radiation by the solid as a function of suspended particulate mass. Experimental evidence regarding the rate of propan-2-ol photo-oxidation under oxygen-purged conditions compared to the observed rate under air, suggests a rate dependence upon the partial pressure of oxygen of P02 1/2 The total photocatalytic mineralisation of aqueous 2-chlorophenol mediated by Degussa P25 TiO2 has been achieved in approximately 5 hours (c0 2CP = 5x10-4M), with an initial zero order rate constant of 1.7x10-4mol.g-1h-1. (6h irradiation period). The kinetics of the reaction are shown to be loosely expressed by the Langmuir-Hinshelwood kinetic model, but complex kinetics were in evidence under conditions of partial mineralisation, which may be dictated by the solution pH and/or the concentration of intermediate degradation products. A mechanism for the photo-oxidation reaction has also been proposed, based upon experimental evidence involving measurements of pH, conductance, carbon dioxide evolution and GCMS studies, which suggests a complex reaction pathway. The photocatalytic mineralisation of a saturated solution of gamma - hexachlorocyclohexane (Lindane, 7ppm), has been achieved in approximately 2 hours by this method and the mechanistic and kinetic details of this reaction are discussed briefly.
Author: M. Schiavello
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 218
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Book Description
Photocatalysis is a reaction which is accelerated by light while a heterogeneous reaction consists of two phases ( a solid and a liquid for example). Heterogeneous Photocatalysis is a fast developing science which to date has not been fully detailed in a monograph. This title discusses the basic principles of heterogeneous photocatalysis and describes the bulk and surface properties of semiconductors. Applications of various types of photoreactions are described and the problems related to the modeling and design of photoreactors are covered.
Author: Khaled M. Mezughi
Publisher:
ISBN:
Category :
Languages : en
Pages : 212
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Book Description
Organic contaminants from industrial and/or domestic effluents may be harmful to humans directly or indirectly by degrading the quality of the aquatic environment. Consequently these contaminants must be reduced to levels that are not harmful to humans and the environment before disposal. Chemical, physical and biological methods exist for the removal of these pollutants from effluents. Among the available chemical methods, heterogeneous photocatalytic oxidation has been found particularly effective in removing a large number of persistent organics in water. In this study, photocatalytic degradation was explored for the removal of reactive azo-dye (textile dye), triclocarban (disinfectant), clopyralid (herbicide) and three endocrine disrupting compounds (EDCs) (estrone, 17?-estradiol and 17?-ethinylestradiol) from synthetic effluents. The major factors affecting the photocatalytic processes including the initial concentration of the target compounds, the amount of catalyst, the light intensity, the type of catalyst, the electron acceptor, the irradiation time and the pH were studied. Other oxidation techniques including (O3, H2O2, UV) were also studied. Generally UV light is used in combination with titanium dioxide, as photocatalyst, to generate photoinduced charge separation leading to the creation of electron-hole pairs. The holes act as electron acceptors hence the oxidation of organics occur at these sites. These holes can also lead to the formation of hydroxyl radicals which are also effective oxidants capable of degrading the organics. The results obtained in this study indicated that photolysis (i.e. UV only) was found to have no effect on the degradation of reactive azo-dye (RO16). However, complete photocatalytic degradation of 20 mg/L (3.24?10-2 mM) RO16 was achieved in 20 minutes in the presence of 1g/L TiO2 Degussa P25 at pH 5.5. Comparison between various types of catalysts (i.e. Degussa P25, VP Aeroperl, Hombifine N) gave varied results but Degussa P25 was the most effective photocatalyst hence it was selected for this study. For RO16 the optimum catalyst concentration was 0.5 g/L TiO2 with initial concentration of 20 mg/L RO16. It was found that the disappearance of RO16 satisfactorily followed the pseudo first-order kinetics according to Langmuir-Hinshelwood (L-H) model. The rate constant was k= 0.0928 mol/min. Photodegradation of TCC was studied in 70%v acetonitrile: 30%v water solutions. UV light degraded TCC effectively and the reaction rates increased with decreasing initial concentration of TCC. UV/TiO2 gave unsatisfactory degradation of triclocarban (TCC) since only 36% were removed in 60 minutes with initial concentration of TCC 20 mg/L. The degradation of clopyralid and the EDCs was studied using three oxidation systems UV/TiO2, UV/H2O2 and O3. Complete degradation of clopyralid (3,6-DCP) was achieved with UV/TiO2 in about 90 minutes at an optimum catalyst concentration of 1g/L. Zero-order kinetics was found to describe the first stage of the photocatalytic reaction in the concentration range 0.078-0.521 mM. At pH 5 the rate constant was 2.09?10-6? 4.32?10-7 M.s-1.Complete degradation of all the three EDCs was achieved with UV/H2O2 in 60 minutes at catalyst concentration of (2.94?10-2 M). On the other hand complete degradation of the EDCs was achieved in just 2 minutes with ozonation. For high concentration EDCs, TiO2/UV gave low efficiency of degradation as compared with ozone and H2O2/UV. First-order kinetics was found to describe the photocatalytic reaction of the EDCs.
Author: Martin M. Halmann
Publisher: CRC Press
ISBN: 9780849324598
Category : Technology & Engineering
Languages : en
Pages : 322
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Book Description
Photodegradation of Water Pollutants, the only complete survey available of current photocatalytic methods for treating water pollutants, covers all aspects of light-stimulated detoxification. Ideal for researchers and students, this new book explains methods for pollution treatment that have proven more effective than conventional biodegradation. Photodegradation of Water Pollutants examines advanced oxidation processes that have been successful in treating the chemical substances produced by industrial effluents and intensive agriculture. These oxidation processes include irradiation with ultraviolet or visible light, the use of homogenous sensitizers, such as dyes, and the use of heterogeneous photocatalysts, such as dispersed semiconductors. In addition, Photodegradation of Water Pollutants addresses the naturally occurring self-cleaning of some pollutants in sunlit surface waters, as well as several alternative non-photochemical approaches to water treatment. Available treatment options are discussed for the main groups of water pollutants, including toxic inorganic ions (cyanides, heavy metals), hydrocarbon derivatives (oil spills, surfactants, pulp and paper wastes), halocarbons, organo-N, organo-P, and organo-S compounds. The text also contains a unique section on the economics of advanced oxidation pollution treatments.
Author: Mario J. Muñoz-Batista
Publisher: Springer Nature
ISBN: 3030494926
Category : Science
Languages : en
Pages : 301
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Book Description
The series Topics in Current Chemistry Collections presents critical reviews from the journal Topics in Current Chemistry organized in topical volumes. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science. The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience. Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field. The chapter "Mechanochemical Forces as a Synthetic Tool for Zero and One-Dimensional Titanium Oxide-Based Nano-photocatalysts" is available open access under a CC BY 4.0 License via link.springer.com.
Author: Helen Chonde Ngwang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Inamuddin
Publisher: Springer Nature
ISBN: 303054723X
Category : Science
Languages : en
Pages : 443
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Book Description
In the context of climate change and fossil fuel pollution, solar energy appears as a cheap and sustainable fuel for many environmental applications, yet the efficiency of techniques has to be improved. This book reviews recent methods and applications of photocatalysis for the treatment of wastewater containing bacteria, heavy metals, organic pollutants, dyes and tannery effluents. Basics of water pollution, polluted river ecosystems and membranes are also detailed.
Author: Craig Steven Turchi
Publisher:
ISBN:
Category :
Languages : en
Pages : 432
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Book Description
Author: Rajendra Pawar
Publisher: William Andrew
ISBN: 0323393136
Category : Technology & Engineering
Languages : en
Pages : 113
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Book Description
In Heterogeneous Nanocomposite-Photocatalysis for Water Purification, the authors introduce various heterogeneous photocatalysts based on novel nanostructures of metal oxide semiconductors and graphene used for water purification, including TiO2, Fe2O3, SnO2, WO3 and g-C3N4, and outlines their advantages and drawbacks. The nanocomposite-photocatalysts ZnO and CdS are compared with reduced graphene oxide (rGO), a rapidly growing materials system. The authors describe how the photocatalytic activity of known nanomaterials can be improved by modifying the structural and optical properties (i.e., phase composition). Introductory portion of the book includes a brief survey of all different kinds of heterogeneous photocatalysts Discusses the possible photocatalysis mechanism occurring during the degradation of different toxic pollutants Provides the photoelectrochemical measurement for synthesized catalysts, supporting the effective transportation of photoelectrons resulting into better catalytic properties
Author: Barbara Bonelli
Publisher: MDPI
ISBN: 3039282867
Category : Science
Languages : en
Pages : 98
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Book Description
The quality of water is not only a technological and scientific issue, but a social and economic problem, in both developed and developing countries. Besides local regulations, which differ between regions and need constant upgrades, significant scientific developments are required in both the detection and removal of water contaminants. This Issue focuses on some recent advancements in the photocatalytic removal of organic pollutants, which is one of the aspects of the problem that involves the need of advanced catalysts and implies significant advancements in the field of materials science and chemical engineering.
