A Statistical Evaluation of the Photocatalytic Degradation of 3-chlorophenol in Aqueous Solution Using UV Light and TiO2 PDF Download
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Author: Shinoka Fujita
Publisher:
ISBN:
Category : Water
Languages : en
Pages : 388
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Author: Shinoka Fujita
Publisher:
ISBN:
Category : Water
Languages : en
Pages : 388
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Author: Chih-Chang Wang
Publisher:
ISBN:
Category : Chlorophenols
Languages : en
Pages : 230
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Book Description
Author: Radwa Elsalamony
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659549106
Category :
Languages : en
Pages : 264
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Book Description
There we will focus on the water pollution which is an important problem. This work aims to study the photocatalytic degradation of chlorophenols. They belong to a notable group of pollutants because of their high toxicity, and hardly biodegradable, and are difficult to remove from the environment. Photocatalytic degradation of chlorophenols using UV light was investigated over mesoporous catalysts. Ti-MCM-41(20), Ti-MCM-41(10), TiO2/MCM-41, Fe-Ti-MCM-41, TiO2/Fe-MCM-41 and TiO2/SBA-15 catalysts were prepared from the corresponding metal salts by the sol-gel technique. The catalyst were investigated using X-ray diffraction (XRD), FT-IR spectroscopes, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and BET surface areas of the samples were determined using the nitrogen adsorption and desorption isotherms. 100 ppm was used as model pollutants. High purity 2,4,6-trichlorophenol and 4-chlorophenol solutions individually and 0.1 g/L of each catalyst was tested at different irradiation times. At each interval time 10 ml of irradiated solution was taken and analyzed by High Performance Liquid Chromatography (HPLC), Ion Chromatography (IC). Aromatic interme
Author: Lindelwa Jay
Publisher:
ISBN:
Category : Water
Languages : en
Pages : 0
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The United States Environmental Protection Agency (USEPA) has enlisted phenolic compounds as pollutants of priority concern, as they tend to persist in the environment over a long period, accumulate and exert toxic effects on humans and animals. The entrance of phenolic compounds into the aquatic environment results from natural, industrial, domestic and agricultural activities. Their presence may be due to the degradation or decomposition of natural organic matter present in the water, through the disposal of industrial and domestic wastes into water bodies and through runoffs from agricultural land. Several specific new technologies, called Advanced Oxidation Processes (AOP), have been developed to eliminate dangerous organic chemicals such as phenol from polluted waters. The photocatalytic process, based on UV irradiated semiconductor (TiO2), represents one of AOP that provide an interesting route to the destruction of many organic substances to CO2, H2O and corresponding mineral acids. TiO2 is usually used as a photocatalyst in two crystal structures: Rutile and Anatase. The photoreactivity of P-25 Degussa, consisting of anatase and rutile (4/1 w/w), exceeds that of pure anatase and rutile in several reaction systems. This study characterised the three TiO2 powder forms by BET, XRD, XRF and SEM analyses to contribute to a better understanding of their physical properties. Anatase was revealed to have 98.4% purity x-ray fluorescence analysis, Degussa at 96.7% and rutile at 75.7% was reported to have the most impurities (~25%). This study investigated the UV/TiO2 photocatalytic degradation of phenol, with emphasis on the effects of; solution pH, catalyst load, initial phenol concentration, dissolved oxygen and UV radiation intensity. Degradation studies were conducted in a batch reactor with photons for catalyst (TiO2) activation supplied by a medium pressure 400 W UV lamp immersed in the pollutant solution housed in a double jacket quartz sleeve, which served as the cooling system for the lamp. Temperature control in the reactor was achieved by circulating cold water through the outer cavity of the quartz sleeve. The reactor contents in all batches were aerated at a flow rate of 10 mL/min. Thorough mixing of the contents of the reactor was achieved by continuous agitation with a magnetic stirrer. The experimental reaction time was set at 60-100minutes. Samples were monitored by GC-MS analysis. Results showed that UV/TiO2 photocatalysis is an effective method for the removal of phenol from wastewaters. The efficiency of the process depends strongly on the experimental conditions. Degradation of organic compounds in water is often accompanied by the formation of several intermediate compounds, some of which may be more toxic than the original pollutant. The carbon-13 isotopic labelling technique was employed to track the degradation mechanism of phenol to better understand the degradation pathway. Carbon-13 tracking results revealed that hydroquinone, catechol, benzoquinone, resorcinol and maleic acid were the main intermediates containing the C-13 isotope. A reaction pathway was postulated based on these findings. Kinetic isotope effect (KIE) experiments were conducted and a primary isotope effect was observed. This confirmed that the C-13 isotope position on the labelled phenol was the site of bond breaking in the rate-limiting step.
Author: Rachel D. Morgan
Publisher:
ISBN:
Category : Chlorophenols
Languages : en
Pages : 166
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Author: Mohammad Ehtisham Khan
Publisher: Elsevier
ISBN: 0443188084
Category : Technology & Engineering
Languages : en
Pages : 283
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Book Description
Metal-chalcogenides have exceptional properties and can be used for electronic devices, environmental monitoring, and sensing applications, for energy storage, as electrode materials, in fuel cells, membranes and for photocatalytic degradation of environmental pollutants in the field of waste-water treatment applications. Metal-Chalcogenide Nanocomposites: Fundamentals, Properties, and Industrial Applications focuses on metal chalcogenide nanomaterials for environmental remediation and corrosion applications. The chapters focuses on cost-effective and facile fabrication approaches, their growth mechanisms, optical, electrical, and other important properties and their applications in a broad range of diverse fields such as photocatalysis, photovoltaics, hydrogen production, lithium batteries, energy storage, anticorrosion, and sensor devices. The book will be an important information source for both material scientists and engineers who want to create the next generation of products and devices for energy and environmental applications. - Covers fabrication, standard characterization, photocatalytic mechanisms, and environmentally-sustainable fabrication methods - Applications covered include environmental, electronics, oil, gas, water treatment, sensing, and many more - Includes challenges and future opportunities, which are discussed in detail
Author: Zakhele Siyanda Prince Khuzwayo
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Polychlorinated endocrine disrupting chemicals are environmental pollutants that are increasingly found in water sources. As a result of their hydrophobic properties, they generally accumulate in adipocytes of humans and wildlife when ingested. In this study, the feasibility of the advanced oxidation processes (AOPs) such as heterogeneous photocatalysis technology is investigated for the treatment of organochlorides in water systems. Titanium dioxide (TiO2) is the semiconductor catalyst of interest. The literature suggests that the most prominent organochlorides in the region are organochloride pesticides (OCPs). A group of 5 compounds were identified for the investigation: DDT, DDE, heptachlor, chlordane, and a polychlorinated biphenyl compound named 2,3,4-trichlorobiphenyl. Reverse phase solid phase extracted (RP-SPE) surface water organic analytes analysis was conducted using gas chromatography mass spectroscopy (GC-MS). Results from most sampling sites showed high concentration levels of the organochlorides in the environment. Heterogeneous photocatalysed mineralisation processes of organochlorides in aqueous systems were conducted in a batch reactor. Organochloride spiked solutions of differing catalyst concentrations are irradiated using a UV lamp for a period of 30 minutes. The reaction kinetics are determined and weighed against conventional photolysis. Results showed improved photo degradation of organochlorides under photocatalytic imposed conditions in comparison to photolysis. Results also suggest that photocatalytic degradation of organochlorides is less favoured with increased TiO2 catalyst concentrations. Enhanced catalyst performance studies through TiO2 surface property modification were conducted using copper nitrate (CuNO3) as a catalyst dopant. The doped catalyst showed slightly improved degradation of organochlorides at particular catalyst concentrations. Simulated photocatalytic rate of reaction kinetics results are in correlation with the modeled experimental results. They show variability of the degradation constant in the rate of reaction with varied catalyst concentrations. Catalyst concentration efficiency of each compound and the rate of the reactions were determined.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Wan Nor Adira Wan Khalit
Publisher:
ISBN:
Category :
Languages : en
Pages : 45
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Author: Khaled M. Mezughi
Publisher:
ISBN:
Category :
Languages : en
Pages : 212
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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.
