Layer by layer TiO2 thin films and photodegradation of Congo red (original) (raw)
Related papers
Surface modified nanostructured-TiO2 thin films for removal of Congo red
Korean Journal of Chemical Engineering, 2018
We synthesized nanostructured TiO 2 thin films by the modified sol-gel template method using the polyethylene glycol as filler media. The TiO 2 surface modification for both the thin films, i.e., template and non-template, was done with the ascorbic acid. All the four thin film samples, S1 (TiO 2 (non-template), TiO 2 (template), S3 (S1 modified with ascorbic acid) and S4 (S2 modified with ascorbic acid), were characterized by various analytical methods. Phase evaluation was monitored by the X-Ray diffraction analysis. Moreover, the thin films particle sizes were obtained to be 22.32, 21.20, 14.52 and 16.77 nm, respectively for the samples S1, S2, S3 and S4. The changes in particle size and morphology due to the PEG and ascorbic acid were determined by scanning electron microscopy (SEM). Similarly, thermal gravimetric (TG) and differential scanning calorimetry (DSC) were performed to determine the decomposition behavior of organic compound present in the solid samples. The functional groups were determined by infrared (IR) analysis. The photocatalytic efficiency, as a reference of Congo red, was conducted using all the four samples of TiO 2 thin films. Complete photocatalytic degradation of Congo red was achieved by these samples within 130, 80, 40 and 30 mins of UV illumination.
Photodegradation of Congo Red catalyzed by nanosized TiO2
Journal of Molecular Catalysis A: Chemical, 2005
The effects of various physical properties (particle size, shape, surface area, crystal structure, and phase composition) on the photocatalytic performance of nanosized TiO 2 were studied through the photodegradation of Congo Red. Kinetic results showed that anatase TiO 2 was a superior photocatalyst to rutile TiO 2 due to the inherent difference in the two crystal structures. Anatase TiO 2 nanorods with predominantly (1 0 1) surface exhibited low activity because the non-dissociative adsorption of H 2 O to this surface retarded the generation of OH • radicals required for facile photocatalytic oxidation. It was found for the first time that the shape of TiO 2 nanocrystals significantly affected their photocatalytic activities. The previously reported anatase-rutile synergetic effect in commercialized mixed-phase TiO 2 (Degussa P25) was not observed in this study, perhaps, due to poor contact between the two phases and the extremely small sizes, as well as the not-optimized phase compositions in the current work.
International Journal of Environmental Science and Technology, 2017
In this study, the photocatalytic degradation of Congo red has been investigated in N-doped TiO 2 (N-TiO 2) aqueous suspensions under visible light irradiation. Visible light-active N-TiO 2 was successfully prepared at three different weight contents (2.5, 5, and 7%) employing sol-gel method. It was able to harvest the visible irradiation with wavelength suitable for activation. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometer, diffused reflectance UV-Vis spectroscopy, nitrogen adsorption Brunauer-Emmert-Teller, Raman spectroscopy, photoluminescence and X-ray photoelectron spectrometer were used to characterize the doped catalyst. The samples had a relatively large specific Brunauer-Emmert-Teller surface areas of about 42 m 2 g-1 with average X-ray diffraction crystalline size of 52 nm and showed visible light photocatalytic activity at about 408 nm. The impacts of several operating parameters on the Congo red photodegradation process were examined. Langmuir-Hinshelwood model exhibited pseudo-firstorder degradation kinetics. N-TiO 2-assisted plausible photodegradation mechanism has been suggested based on the qualitatively detected intermediate compounds.
Journal of hazardous …, 2005
Electrochemical-assisted photodegradation of methyl orange has been investigated using TiO 2 thin films. The films were prepared by sol-gel dip-coating method. Several operational parameters to achieve optimum efficiency of this electrochemical-assisted photodegradation system have been tested. Photoelectrochemical degradation was studied using different light sources and light intensity. The light sources chosen ranged from ultraviolet to visible light. The effect of agitation of the solution at different speeds has also been studied. Slight improvement of photodegradation rate was observed by applying higher agitation speed. Investigation on the electrode after repeated usages show the electrode can be reused up to 20 times with percentage of deficiency less than 15%. The study on the effect of solution temperature indicated that the activation energy of the methyl orange degradation is 18.63 kJ mol −1 .
Molecules
TiO2 thin films were deposited on quartz substrates by metal–organic chemical vapor deposition (MOCVD) at temperatures of 250, 350, and 450 °C. X-ray diffraction (XRD) data revealed the production of a pure anatase phase, a decrease in crystallite size, and a textural change as deposition temperature increased. Atomic force microscopy (AFM) was used to study the morphological properties and confirm XRD results. UV-Vis.-NIR spectroscopy was used to investigate the optical properties of the samples. The effect of deposition temperature on wettability was investigated using contact angle measurements. Sunlight photocatalytic properties increased with the increase in deposition temperature for methyl orange and methylene blue. Films were post-annealed at 500 °C for 2 h. The effect of annealing on all the above-mentioned properties was explored. The kinetic analysis demonstrated superb agreement with the kinetic pseudo-first-order model. The rate of photocatalytic degradation of MB was ~...
The influence of TiO2 powder and film on the photodegradation of methyl orange
Materials Chemistry and Physics, 2008
Recent investigation has showed that the semiconductor nano-powder or thin film, such as titanium dioxide suspended in water, can utilize ultraviolet light for photocatalytic oxidation of organic pollutants, such as dyes. The photocatalytic activity of TiO 2 (powder or thin film) was tested in the reaction of photodegradation of methyl orange (MO). The effect of the initial concentration of dye, the pH, the amount and the type of TiO 2 have been investigated. The films were prepared by doctor blade technique, and were annealed in air at various temperatures ranging from 300 to 500 • C. The thermal treatment increases the surface roughness of thin films. The best film (without fissures), with higher pores and small grains (150 nm) was the annealed one at 500 • C. The correlation between the measured contact angle and the films roughness estimated from atomic force microscopy (AFM) shows that a low contact angle (wetting behavior) corresponds to a higher porosity (a fractured structure, rich in edges and corners), and consequently to high surface energy. Kinetic analyses indicate that the photodegradation rates of dyes can usually be approximated as first-order kinetics for degradation mechanisms. Adsorption is a prerequisite for the TiO 2 -assisted photodegradation, and the extent of degradation has been discussed in terms of the Langmuir-Hinshelwood model. Thin-film coating of photocatalyst may solve the problems of leaching and separation. At a low concentration of MO (0.0125 mM) the efficiency of MO photodegradation is comparable in the case of thin film and powder of TiO 2 .
Journal of Physics: Conference Series, 2014
Nanosized TiO2 films were deposited by spray pyrolysis and thermally treated at 400 o C. Then the films were dipped in 1M aqueous solution of HCl. The activated samples were divided into two parts -one part was dried (A) and another was annealed (AT) in air. The photocatalytic degradation of Reactive Black (RB5) textile dye under visible light was tested. The following instrumental methods: X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied for the phase and surface characterization of obtained samples. According to Raman and XRD analyses all films are anatase. The XRD showed that activated films are better crystallized than non activated TiO2 film. The presence of chlorine at 200.3 eV was registered for acid activated samples by X-Ray photoelectron spectroscopy. The acidic activated films exhibited higher rate of dye photodegradation than that of the reference TiO2 sample. The photocatalytic efficiency decreases in the order A > AT> non activated TiO2 films. The degradation rate constant for acid activated films is two times higher than those of the reference film. The hydroxyl content in TiO2 acidic activated films is greater than that of the non-activated films, which results in significant increase in the photocatalytic activity. In addition, the presence of chlorine may also lead to enhancement in efficiency.