Influence of TiO2 morphological parameters in dye photodegradation: A comparative study in peroxo-based synthesis (original) (raw)
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The Role of the Relative Dye/Photocatalyst Concentration in TiO2Assisted Photodegradation Process
Photochemistry and Photobiology, 2013
Despite photocatalytic degradation is studied generally focusing the catalyst, its interaction with the contaminant molecule plays a fundamental role in the efficiency of that process. Then, we proposed a comparative study about the photodegradation of two well-known dyes, with different acidity/basicity-Methylene Blue (MB) and Rhodamine B (RhB), catalyzed by TiO 2 nanoparticles, varying both dye and photocatalyst concentrations. The results showed that the amphoteric character of MB molecules, even in a range of concentration of 5.0-10.0 mg L À1 , did not imply in pH variation in solution. Therefore, it did not affect the colloidal behavior of TiO 2 nanoparticles, independent of the relative dye/catalyst concentration. The acid-base character of RhB influenced the resultant pH of the solution, implicating in different colloidal behavior of the nanoparticles and consequently, in different degradation conditions according to dye concentration. As the isoelectric point of TiO 2 is between the pH range of the RhB solutions used in this study, from 1.0 to 7.5 mg L À1 , the resultant pH was the key factor for degradation conditions, from a well dispersed to an agglomerated suspension. MATERIALS AND METHODS For this study, TiO 2 (Aldrich nanopowder, 99.7% purity) and the salts MB and RhB P.A. (VETEC, >99%) were used without further purification. X-Ray Diffraction (XRD) analysis of the oxide was carried out with a Rigaku Dmax 2500-PC X-ray diffractometer with Cu Ka source (1.5456 A). Crystallographic coherence lengths were calculated according
Journal of Photochemistry and Photobiology A: Chemistry, 2003
Anionic (Alizarin S (AS), azo-Methyl Red (MR), Congo Red (CR), Orange G (OG)) and cationic (Methylene Blue (MB)) dyes were degraded, either individually or in mixtures, by using UV-irradiated TiO 2 in suspension or supported on glass and on paper. The influence of the chemical structure of different dyes as well as that of pH and of the presence of inorganic salts on the photocatalytic properties of TiO 2 has been discussed. The role of adsorption is suggested, indicating that the reaction occurs at the TiO 2 surface and not in the solution. S and N hetero-atoms are respectively mineralized into SO 4 2− , NO 3 − and NH 4 + , except azo-groups which mainly formed N 2 which represents an ideal case for a decontamination reaction. The fate of nitrogen strongly depends on its initial oxidation degree. High photocatalytic activities have been found for TiO 2 coated on glass by the sol-gel method. Its efficiency was intermediate between those of PC-500 and P-25 powders. The efficiency of PC-500 TiO 2 sample, fixed on paper by using a binder, is slightly less important than that of the powder. The presence of a silica-binder with an acidic pzc is suggested to be at the origin of the decrease in efficiency.
Photocatalytic Activity of Defective TiO2-x for Water Treatment/Methyl Orange Dye Degradation
Chemistry & Chemical Technology
This study is designed to highlight photocatalytic activity of TiO2 nanoparticles in methyl orange (MO) dye degradation. Titanium dioxide TiO2 nanopowder was synthesized by conventional sol-gel method and calcined in air atmosphere at different temperatures 350C, 550C and 850C. The prepared TiO2 nanoparticles then were subjected to a solid state reaction with calcium hydride (CaH2) at the same temperatures but calcined in argon atmosphere. X-Ray Diffraction (XRD) measurements used for phase and crystalline size identification showed that the obtained samples have the same TiO2 anatase phase, but the crystalline size decreased after reduction treatment. The electronic properties obtained via UV spectroscopy showed the decrease in calculated energy gap from 3.3 eV for prepared TiO2-550 to 2.65 eV for reduced TiO2-CaH2-550, which extend the absorption spectra toward visible light region. Energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM) measurements reveale...
Journal of Molecular Catalysis A: Chemical, 2007
Titanium dioxides (TiO 2 ) nanoparticles with one-dimensional (1D) geometry, nanorods and nanostripes, were used as photocatalysts to photodegrade Rhodamine B (RhB) under ultraviolet (UV) and visible irradiation. The nanorods catalyst exhibited very interesting photocatalytic properties: under the UV irradiation its catalytic activity was slightly below that of the well-known TiO 2 catalyst P25, while under visible light it exhibited a better activity than P25.
The total annual production of synthetic dye is more than 7 Â 10 5 tons. Annually, through only textile waste effluents, around one thousand tons of non-biodegradable textile dyes are discharged into natural streams and water bodies. Therefore, with growing environmental concerns and environmental awareness there is a need for the removal of dyes from local and industrial water effluents with a cost effective technology. In general, these dyes have been found to be resistant to biological as well as physical treatment technologies.
Nanostructured mesoporous TiO2 particles with high specific surface area and average crystallite domain sizes in the range of 2 nm-30 nm have been synthesized via sol-gel and hydrothermal techniques. The as-produced nanoparticles have been characterized via X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, Fourier Transform Infra-Red, and Raman Spectroscopy as a function of temperature for their microstructure, morphology, optical, porosity and absorption properties. The as-synthesized TiO2 nanostructures were attempted as catalysts in the photocatalytic degradation of Rhodamine B and Sudan III dyes in a batch reactor under UV light. The results show that for catalysts calcined at 300 °C, ~100 % degradation of Sudan III dye was observed when Hydrothermal based catalyst was used whiles ~ 94 % degradation of Rhodamine B dye was observed using the sol-gel based catalysts. These synthesized TiO2 nanoparticles have promising potential applications in the degradation of a wide range of dye pollutants.
This paper presents the review of the effects of operating parameters on the photocatalytic degradation of textile dyes using TiO 2-based photocatalysts. It further examines various methods used in the preparations of the considered photocatalysts. The findings revealed that various parameters, such as the initial pH of the solution to be degraded, oxidizing agents, temperature at which the catalysts must be calcined, dopant(s) content and catalyst loading exert their individual influence on the photocatalytic degradation of any dye in wastewaters. It was also found out that sol–gel method is widely used in the production of TiO 2-based photocatalysts because of the advantage derived from its ability to synthesize nanosized crystallized powder of the photocatalysts of high purity at relatively low temperature.
Nanostructured mesoporous titanium dioxide (TiO 2) particles with high specific surface area and average crystallite domain sizes within 2 nm and 30 nm have been prepared via the sol-gel and hydrothermal procedures. The characteristics of produced nanoparticles have been tested using X-Ray Diffraction (XRD), BrunauereEmmetteTeller (BET) surface area analysis, Scanning Electron Microscopy (SEM), Fourier Transform Infra-Red (FTIR), and Raman Spectroscopy as a function of temperature for their microstructural, porosity, morphological, structural and absorption properties. The as-synthesized TiO 2 nanostructures were attempted as catalysts in Rhodamine B and Sudan III dyes' photocatalytic decomposition in a batch reactor with the assistance of Ultra Violet (UV) light. The results show that for catalysts calcined at 300 C, w100 %
Revista Facultad …, 2011
In this work, TiO 2 photocatalysts were synthesized using a conventional sol-gel and hydrothermal synthesis methods with steam pressure treatment. Photocatalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectra (DRS) and N 2 adsorption-desorption. The photoactivity of the samples was analyzed towards the photooxidation of the azo dye Orange II (Or-II) and phenol using different illumination setups to compare the activity features of photocatalysts. The effect of the synthesis variables such as the synthesis route, water/alcoxide and alcohol/alcoxide ratios, as well as the alcohol type was analyzed. TiO 2 photocatalysts obtained by hydrothermal synthesis have a better photoactivity than the particles synthesized by the chosen sol-gel route, reaching the Or-II degradation photoactivity of the commercial TiO 2 P25. On the other hand, the water/alcoxide ratio and alcohol type have a marked effect on the photoactivity of the hydrothermal synthesized TiO 2 , whereas the alcohol/alcoxide ratio does not have a relevant effect on the Or-II degradation photoactivity.
Effect of Dye Structure on the Photodegradation Kinetic Using TiO<sub>2</sub> Nanoparticles
Journal of Materials Science and Chemical Engineering
In this study the effect of pH, adsorption behavior and the chemical structures of two dyes (Methyl Orange and Bromothymol Blue) on the photodegradation rate constant, was investigated. Adsorption isotherm shows that the adsorption amount of dyes on TiO 2 surface is highly related to the pH of the solution and to the pKa of each dye. In acidic medium the adsorption percentage of Methyl Orange on TiO 2 surface was 76% facing 5% for Bromothymol Blue. The kinetic study shows compatibility between the degradation rate constant and the adsorption percentage on the surface. In basic medium the adsorption percentage of Methyl orange and Bromothymol Blue is similar while the degradation rate of Methyl orange is two times faster than that of Bromothymol Blue which reveals the role of chemical structure in the photodegradation rate.