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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.
Effect of Oxygen and Hydrogen Peroxide on the Photocatalytic Degradation of Monochlorobenzene in Aqueous Suspension  [PDF]
Dyi-Hwa Tseng,Lain-Chuen Juang,Hsin-Hsu Huang
International Journal of Photoenergy , 2012, DOI: 10.1155/2012/328526
Abstract: The influences of oxygen and hydrogen peroxide ( ) on the degradation and mineralization of monochlorobenzene (MCB) during UV/ process were investigated. Experimental results indicated that oxygen was a determining parameter for promoting the photocatalytic degradation. The presence of oxygen reduced the illumination time needed for the complete decay of MCB from 240 to 120?min. The photocatalytic degradation of MCB in UV/ / photocatalysis followed a simplified two-step consecutive kinetics. The rate constants of degradation ( ) and mineralization ( ) were increased from 0.016 to 0.046?min?1 and from 0.001 to 0.006?min?1, respectively, as the initial concentration of dissolved oxygen (DO) was increased from 1.6 to 28.3?mg?L?1. Owing to the fact that acted as an electron and hydroxyl radicals ( ) scavenger, the addition of should in a proper dosage range to enhance the degradation and mineralization of MCB. The optimal dosage for MCB degradation was 22.5?mg?L?1, whereas the most efficient dosage for MCB mineralization was 45.0?mg?L?1. In order to minimize the adverse effects of higher dosage, including the capture of radicals and competitive adsorption, and to improve the photocatalytic degradation of MCB, the sequential replenishment of was suggested. For the stepwise addition of a total dosage of 45.0?mg?L?1, a complete destruction of MCB was observed within 120?min of irradiation. Additionally, the mineralization efficiency was about 87.4% after 240?min of illumination time. 1. Introduction During last several decades, the control of organic pollutants has received much attention for its considerable amount and variety. However, the conventional biological, physical, and chemical technologies are ineffective and limitative toward the destruction of toxic and recalcitrant organic pollutants. Heterogeneous photocatalysis, one of the so-called Advanced Oxidation Processes (AOPs), offers an advanced oxidation capable of pollutant abatement [1, 2]. Many researchers have concluded that the UV/TiO2 process is a promising technology for the degradation and mineralization of organic substrates to harmless final products in air and water media [3–6]. The mechanism of the UV/TiO2 process has been discussed extensively in the literature [7–9]. When TiO2 is irradiated with light energy equal to or higher than its band-gap, an electron ( ) can be excited from the valence band to the conduction band and leaving a hole ( ) in the valence band If charge separation is maintained, the paired may migrate to the surface of the photocatalyst. In aqueous phase, the
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
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.
Photocatalytic degradation of reactive dye RED-3BA in aqueous suspension under UV-visible light  [PDF]
Nguyen Thi Dung,Nguyen Van Khoa,Jean-Marie Herrmann
International Journal of Photoenergy , 2005, DOI: 10.1155/s1110662x05000024
Abstract: The photo-catalytic degradation efficiency of several commercial titania powders (Degussa P-25 and Ishihara Sangyo ST-01) and of TiO2 supported on diatomite were investigated in the degradation of a reactive dye (RED-3BA) under UV-Visible light. The observed rate constant for Degussa P-25 was found to be higher than that achieved by using Ishihara Sangyo ST-01 (kobs=3.3×10−2min−1 for Degussa P-25 and 4×10−4min−1 for Ishihara Sangyo ST-01). This could be related to the amount of basic hydroxyl groups on the surface of TiO2 particles as shown in the IR spectra. TiO2 Degussa P-25 supported on diatomite was prepared by dip-coating method. The photo-catalytic activity of supported TiO2 was twice smaller than TiO2 Degussa P-25 (kp-25=3.3×10−2min−1;kp25/diatomite=1.6×10−2min−1). The higher surface areas of ST-01 and the TiO2/diatomite could not lead to a higher degradation rate and to a higher degree of mineralization but TiO2/diatomite could be separated more promptly and more easily from the solution. The effect of pH was investigated in the range 4–9. Acidic (pH = 4) medium was found to favor the adsorption and degradation rate with P-25 particles.
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.
New Porphyrin/Fe-Loaded TiO2 Composites as Heterogeneous Photo-Fenton Catalysts for the Efficient Degradation of 4-Nitrophenol  [PDF]
Giuseppe Mele,Iolanda Pio,Anna Scarlino,Ermelinda Bloise,Roberta Del Sole,Leonardo Palmisano,Giuseppe Vasapollo
Journal of Catalysts , 2013, DOI: 10.1155/2013/376078
Abstract: A new class of porphyrin(Pp)/Fe co-loaded TiO2 composites opportunely prepared by impregnation of [5,10,15,20-tetra(4-tert-butylphenyl)] porphyrin (H2Pp) or Cu(II)[5,10,15,20-tetra(4-tert-butylphenyl)] porphyrin (CuPp) onto Fe-loaded TiO2 particles showed high activities by carrying out the degradation of 4-nitrophenol (4-NP) as probe reaction in aqueous suspension under heterogeneous photo-Fenton-like reactions by using UV-visible light. The combination of porphyrin-Fe-TiO2 in the presence of H2O2 showed to be more efficient than the simple bare TiO2 or Fe-TiO2. 1. Introduction Nowadays, due to the increasing presence of refractory molecules in the wastewater streams, it is important to develop new technologies to degrade such recalcitrant pollutant molecules into smaller innocuous ones. For this reason efficient oxidation processes operating under environmentally friendly conditions are needed [1]. As well known, Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species such as the hydroxyl radical and possibly others. In the last few years, Fenton-like reactions, in combination with other advanced oxidation processes, are assuming fundamental and practical perspectives in water treatment processes [2, 3]. The combination of various technologies, in fact, is often effective to achieve a complete mineralization of the pollutant(s) present in the starting effluents because many stable products of environmental concern can be persistent after the treatment by Fenton reaction. Recently, the utilization of TiO2 as catalyst for the photooxidation of organic pollutants in water is becoming a relevant topic in view of a possible application in economically advantageous and environmentally friendly processes not only performed with the aim to abate pollutants but also for synthetic purposes [4–8]. Various advanced oxidation technologies have been used in the presence of TiO2, H2O2, and irradiation to enhance the efficiency of the overall photodegradation process [9–12]. Also, in the last years, dye-sensitized TiO2-based materials have been employed for improving the efficiency of energy light conversion towards photocatalytic processes [13–19]. In this work the design of novel composites metal free or Cu-porphyrin/Fe co-loaded TiO2 as well as their application as catalytic systems for photoassisted heterogeneous Fenton-like reactions has been reported. In particular, we demonstrated that the presence of porphyrins and Fe species co-loaded onto the TiO2 surface along with H2O2 in the reacting medium
Transition metal doped : physical properties and photocatalytic behaviour  [PDF]
A. Di Paola,S. Ikeda,G. Marcì,B. Ohtani,L. Palmisano
International Journal of Photoenergy , 2001, DOI: 10.1155/s1110662x01000216
Abstract: Two probe photocatalytic reactions, i.e. ethanoic acid and 4-nitrophenol photooxidation, were carried out in different experimental conditions by using suspensions of transition metal (Co, Cr, Cu, Fe, Mo, V and W) doped polycrystalline TiO2 powders in aqueous systems. A beneficial influence of the presence of metal species was observed only with the samples containing copper and tungsten. In particular, the TiO2/Cu powders showed to be more photoactive of bare TiO2 for the ethanoic acid oxidation while the TiO2/W samples were more efficient for 4-nitrophenol degradation. A tentative interpretation is provided on the basis of the values of the points of zero charge of the powders and of the rate constants of recombination of photogenerated electrons and holes, determined by femtosecond pump-probe diffuse reflectance spectroscopy (PP-DRS).
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
Solar photocatalitic degradation of Vat Yellow 4 dye in aqueous suspension of TiO2 - optimization of operational parameters  [PDF]
Sullipalayam K. Kavitha,Pachakoundanpalayam N. Palanisamy
Advances in Environmental Sciences , 2010,
Abstract: The photocatalytic decolourisation and degradation of an anthraquinone dye Vat Yellow 4 inaqueous solution with TiO2-P25 (Degussa) as photocatalyst in slurry form has been investigated undersolar irradiation and UV irradiation. The study on the effect of various photocatalysts on the degradationreveals that TiO2 is the best catalyst in comparison to other commercial photocatalysts. The effects ofvarious operational parameters such as catalyst loading, initial dye concentration and pH on thedecolourisation and degradation under solar irradiation in TiO2 suspension have been investigated to findout the optimum conditions. The decolourisation and degradation kinetics have been analysed. Bothfollow first-order kinetics. A study on the effect of electron acceptors on photo oxidation reveals thatboth decolourisation and degradation increase in the presence of the electron acceptors such as H2O2and (NH4)2S2O8 up to an optimum dosage beyond which the enhancement effect is negligible. Thecomparison between thin-film coating of TiO2 and aqueous slurry method reveals that slurry method ismore efficient.
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