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Kinetics of photocatalytic decomposition of Fenuron over in aqueous solution  [PDF]
Ouarda Brahmia,Abdelaziz Boulkamh,Tahar Sehili,Jean-Pierre Aguer,Claire Richard
International Journal of Photoenergy , 2002, DOI: 10.1155/s1110662x02000132
Abstract: The kinetics of the photocatalytic degradation of Fenuron (3-phenyl-1,1-dimethylurea) in aqueous suspension of several semiconductors irradiated at 365nm has been investigated. The kinetics of the reaction is well described by the Langmuir-Hinshelwood model showing that the degradation reactions occur on the semiconductors particles surface. The primary photoproducts were identified by RMN and GC/MS. The main initial reaction is hydroxylation in ortho and para position with respect to the urea function. The rate of the photocatalytic degradation increases upon addition of small amounts of hydrogen peroxide, but is slightly reduced by chloride ions.
Dispersion and Stabilization of Photocatalytic TiO2 Nanoparticles in Aqueous Suspension for Coatings Applications
Siti Hajar Othman,Suraya Abdul Rashid,Tinia Idaty Mohd Ghazi,Norhafizah Abdullah
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/718214
Abstract: To produce titanium dioxide (TiO2) nanoparticle coatings, it is desirable that the nanoparticles are dispersed into a liquid solution and remain stable for a certain period of time. Controlling the dispersion and aggregation of the nanoparticles is crucial to exploit the advantages of the nanometer-sized TiO2 particles. In this work, TiO2 nanoparticles were dispersed and stabilized in aqueous suspensions using two common dispersants which were polyacrylic acid (PAA) and ammonium polymethacrylate (Darvan C). The effect of parameters such as ultrasonication amplitude and type and amount of dispersants on the dispersibility and stability of the TiO2 aqueous suspensions were examined. Rupture followed by erosion was determined to be the main break up mechanisms when ultrasonication was employed. The addition of dispersant was found to produce more dispersed and more stabilized aqueous suspension. 3 wt.% of PAA with average molecular weight () of 2000 g/mol (PAA 2000) was determined to produce the best and most stable dispersion. The suspensions were then coated on quartz glass, whereby the photocatalytic activity of the coatings was studied via the degradation of formaldehyde gas under UV light. The coatings were demonstrated to be photocatalytically active.
Solar Photocatalytic Degradation of Azo Dye in Aqueous Suspension Assisted by Fresnel Lens  [PDF]
Wen-Shiuh Kuo,Wen-Yu Chen
International Journal of Photoenergy , 2012, DOI: 10.1155/2012/303586
Abstract: Solar TiO2 photocatalytic process assisted by a Fresnel lens was investigated for treating an azo dye wastewater of Acid Orange 10 (AO10). Response surface methodology (RSM) was employed to assess the effect of critical process parameters (including initial pH of wastewater, concentration of TiO2, and reaction time) on treatment performance in terms of COD and TOC degradation efficiency. Optimized reaction conditions based on the analysis of RSM were established under an initial pH of 6.0, a concentration of TiO2 of 1?g/L, and a reaction time of 2?h for reaching a 90% COD and TOC degradation of AO10 wastewater. With the assistance of Fresnel lens, the TOC degradation rate of AO10 wastewater increased significantly from 0.606?h?1 and 0.289?h?1 to 1.477?h?1 and 0.866?h?1 in summer (June) season (UV280–400?nm?nm: 39.9–44.8?W/m2) and winter (December) season (UV280–400?nm?nm: 23.9–26.9?W/m2), respectively. This could be mainly due to the concentrating effect of Fresnel lens for solar energy, resulting in an increase of 2~2.5 times of solar light intensity and a raising heat irradiation in terms of 10~15?°C of wastewater temperature. These results revealed that solar energy could be concentrated effectively by using Fresnel lens and showed a significant promoting effect on the TiO2 photocatalytic degradation of dye wastewater. 1. Introduction Over 100,000 different types of dyes are commercially available and 700,000 tons are produced yearly all over the world. Nearly 50% of these dyes are azo-type dyes [1]. Azo dyes, aromatic moieties linked together by azo (–N=N–) chromophores, represent the largest class of dyes used in textile processing and other industries. The release of these compounds into the environment is undesirable, because the color matters and their toxic breakdown products can be mutagenic [2]. In addition, due to the complex aromatic structure and stability of the azo-dyes, conventional biological treatments are ineffective for degradation and mineralization of the dye molecules [3]. Instead, activated carbon adsorption or coagulation is commonly used. However, new environmental laws may consider the spent adsorbents or sludge as hazardous waste and require further treatment. Consequently, intensive research for novel technologies with higher efficiency and less amount of waste generated has been stimulated. Advanced oxidation processes (AOPs) have been previously described as a promising option to remove persistent pollutants from contaminated water [4]. AOPs are able to produce a highly reactive, nonspecific oxidant, mainly hydroxyl
Photocatalytic Degradation of 2,4-dichlorophenol in Irradiated Aqueous ZnO Suspension  [cached]
Umar Ibrahim Gaya,Abdul Halim Abdullah,Zulkarnain Zainal,Mohd Zobir Hussein
International Journal of Chemistry , 2010, DOI: 10.5539/ijc.v2n1p180
Abstract: This paper focuses on the destruction of aqueous 2,4-dichorophenol in ZnO suspension irradiated by low wattage UV light at 299 K. The operating variables studied include initial 2,4-dichlorophenol concentration, photocatalyst doses and pH. At 1.5 g l-1 feed concentration of ZnO and 50 mg l-1 initial 2,4-dichlorophenol level, a complete degradation was achieved in 180 min. The decomposition kinetics with respect to 2,4-dichlorophenol approximates pseudo zero-order with rate constant peaking at 0.38 mg l-1 min-1. High performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) detected benzoquinone, 2-chlorohydroquinone, 4-chlorophenol, 3,5-dichlorocatechol, hydroquinone, 4-hydroxybenzaldehyde and phenol during the ZnO-assisted photodegradation of 2,4-dichlorophenol among which some pathway products are disclosed for the first time. The reaction mechanism accounting for the degradation pathway intermediates is proposed. Inorganic anion additives such as S2O8 2-, SO4 2-, Cland HPO4 2- manifested inhibition against 2,4-dichlorophenol removal.
Photocatalytic Degradation of p-Nitrophenol (PNP) in Aqueous Suspension of TiO2  [PDF]
Shafiqul Islam, Sumon Kumar Bormon, Md. Nadim, Kamrul Hossain, Ahsan Habib, Tajmeri Selima Akhter Islam
American Journal of Analytical Chemistry (AJAC) , 2014, DOI: 10.4236/ajac.2014.58057
Abstract: The effects of initial concentrations of PNP, doses of TiO2, cations and anions have been investigated to find out the conditions for the maximum degradation of PNP in presence of 254 nm UV light. The rate of photocatalytic degradation of PNP was increased with increasing TiO2 dose until the dose concentration reached at a value 0.4 g/100 mL. Further increase of TiO2 decreased the degradation. The maximum degradation of PNP was found with the catalyst dose 0.4 g/100 mL at pH 3. The degradation of PNP was decreased with increasing of PNP concentration. About 90% degradation of PNP was observed when 1.0 × 10﹣4 M PNP was irradiated for 2 hours in 0.4 g/100 mL of TiO2 suspension. The effect of Cu(II) and Fe(II) ions on the degradation was also investigated. Addition of Cu(II) ions enhances the percent degradation but excess of Cu(II) ions decreases the degradation. Under the same experimental conditions, the presence of \"\" and \"\" is found to be detrimental to the photodegradation of PNP. Hydrogen ion concentration of reaction mixture was found to increase continuously during photodegradation suggesting mineralization of PNP.
Photocatalytic Degradation of Chlorobenzene by TiO2 in High-Temperature and High-Pressure Water  [PDF]
N. Kometani,S. Inata,A. Shimokawa,Y. Yonezawa
International Journal of Photoenergy , 2008, DOI: 10.1155/2008/512170
Abstract: A fluidized-bed-type flow reactor available for the photocatalytic treatment of the suspension of model soil under high-temperature, high-pressure conditions was designed. An aqueous suspension containing hydrogen peroxide (H2O2) as an oxidizer and inorganic oxides as a model soil, titania (TiO2), silica (SiO2), or kaoline (Al2Si2O5(OH)4) was continuously fed into the reactor with the temperature and the pressure controlled to be T=20 ¢ € “400 ¢ C and P ¢ € ‰= ¢ € ‰30 ¢ € ‰MPa, respectively. The degradation of chlorobenzene (CB) in water was chosen as a model oxidation reaction. It appeared that most of the model soils are not so harmful to the SCWO treatment of CB in solutions. When the TiO2 suspension containing H2O2 was irradiated with near-UV light, the promotion of the degradation caused by photocatalytic actions of TiO2 was observed at all temperatures. Persistence of the photocatalytic activity in the oxidation reaction in high-temperature, high-pressure water would open up a possibility of the development of the hybrid process based on the combination of SCWO process and TiO2 photocatalysis for the treatment of environmental pollutants in soil and water, which are difficult to handle by conventional SCWO process or catalytic SCWO process alone.
Aqueous photocatalytic oxidation of lignin and humic acids with supported TiO 2
Sergei Preis,Juha Kallas
International Journal of Photoenergy , 2006,
Abstract: The photocatalytic oxidation (PCO) of UV-irradiated aqueous solutions containing humic acids and lignin was studied. The photocatalyst TiO 2 was attached to buoyant hollow glass microspheres and glass plates. A maximum oxidation efficiency as low as 1.1 and 2.54 mg W 1 h 1 for humic acids and lignin, respectively, was achieved in neutral and alkaline media with 25 gm 2 of the buoyant catalyst. In acidic media, efficiency was even lower. The photocatalytic efficiency with the photocatalyst attached to glass plates was about 3 to 4 times higher than that for the buoyant catalyst. Ferrous ions added to acidic solutions did not increase the rate of PCO of humic acids. However the addition of Fe 2+ ions, up to 0.05 mM, to the lignin solution leads to a dramatic increase, about 25%, in PCO efficiency. A further increase in ferrous ion concentration results in a decrease in the PCO efficiency of lignin. Proceeding most likely by a radical mechanism, the efficiency of PCO of humic acids did not benefit from an excessive presence of hydroxyl radical promoters, such as hydrogen peroxide, although the reaction rate increased. However, PCO of lignin in the acidic medium, where OH.-radical formation is suppressed, benefited from the introduction of hydrogen peroxide due to promoted radical formation.
Aqueous Photocatalytic Oxidation of Lignin: The Influence of Mineral Admixtures  [PDF]
Elina Portjanskaja,Sergei Preis
International Journal of Photoenergy , 2007, DOI: 10.1155/2007/76730
Abstract: The photocatalytic oxidation (PCO) of UV-irradiated aqueous solutions containing lignin on TiO2 was studied for the influence of ferrous ions. The addition of Fe2
Photocatalytic Degradation of Pesticides in Natural Water: Effect of Hydrogen Peroxide
Natividad Miguel,María P. Ormad,Rosa Mosteo,José L. Ovelleiro
International Journal of Photoenergy , 2012, DOI: 10.1155/2012/371714
Abstract: The aim of this paper is to evaluate the effectiveness of photocatalytic treatment with titanium dioxide in the degradation of 44 organic pesticides analyzed systematically in the Ebro river basin (Spain). The effect of the addition of hydrogen peroxide in this treatment is studied, and a monitoring of effectiveness of photocatalytic processes is carried out by measurements of physical-chemical parameters of water. The application of photocatalytic treatment with 1 g L−1 of TiO2 during 30 minutes achieves an average degradation of the studied pesticides of 48%. Chlorine demand, toxicity, and dissolved organic carbon (DOC) concentration of water are reduced. If hydrogen peroxide is added with a concentration of 10 mM, the average degradation of pesticides increases up to 57%, although chlorine demand and toxicity of water increase while DOC concentration remains unchanged with this treatment. The application of either photocatalytic treatments does not produce variations in the physical-chemical parameters of water, such as pH, conductivity, colour, dissolved oxygen, and hardness. The pesticides which are best degraded by photocatalytic treatments are parathion methyl, chlorpyrifos, α-endosulphan, 3,4-dichloroaniline, 4-isopropylaniline, and dicofol while the worst degraded are HCHs, endosulphan-sulphate, heptachlors epoxide, and 4,4′-dichlorobenzophenone.
Photocatalytic degradation of Phenol Red using complexes of some transition metals and hydrogen peroxide  [PDF]
Journal of the Serbian Chemical Society , 2008,
Abstract: The photocatalytic degradation of Phenol Red was investigated using thiocyanate complexes of iron, copper, cobalt and hydrogen peroxide. The rate of photocatalytic degradation of the dye was followed spectrophotometrically. The effect of the variation of different parameters, such as pH, concentration of the complexes and dye, amount of H2O2 and light intensity on the rate of photocatalytic degradation was also studied. A tentative mechanism for the photocatalytic degradation of Phenol Red is proposed.
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