Novel integrated reactor for evaluation of activity of supported photocatalytic thin films: Case of methylene blue degradation on TiO2 and nickel modified TiO2 under UV and visible light

Stefanov, B.; Kaneva, Nina; Puma, Gianluca Li; Dushkin, Ceco D.

doi:10.1016/j.colsurfa.2010.11.026

Cited by 22 publications

(20 citation statements)

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“…They will be referred to as sample "<101>" corresponding to the sample with 2% <001> orientation (i.e., almost randomly oriented grains dominated by <101> facets), and sample "<001>" with 25% <001> orientation. The experiments with MB were performed in a liquid-phase reactor employing in situ laser colorimetry for chemical analysis of the MB concentration employing a λ = 365 nm diode laser, as described in detail elsewhere [29]. A standard 4 W UV tube (λ = 365 nm) was used as a light source, positioned above the sample and attached on a stand, allowing for the distance between the tube and the reaction cell to be changed, as well as the illumination intensity.…”

Section: Photocatalytic Measurementsmentioning

confidence: 99%

Tuning the Photocatalytic Activity of Anatase TiO2 Thin Films by Modifying the Preferred <001> Grain Orientation with Reactive DC Magnetron Sputtering

Stefanov

Österlund

2014

Coatings

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Anatase TiO 2 thin films were deposited by DC reactive magnetron sputtering on glass substrates at 20 mTorr pressure in a flow of an Ar and O 2 gas mixture. The O 2 partial pressure (P O2 ) was varied from 0.65 mTorr to 1.3 mTorr to obtain two sets of films with different stoichiometry. The structure and morphology of the films were characterized by secondary electron microscopy, atomic force microscopy, and grazing-angle X-ray diffraction complemented by Rietveld refinement. The as-deposited films were amorphous. Post-annealing in air for 1 h at 500 °C resulted in polycrystalline anatase film structures with mean grain size of 24.2 nm (P O2 = 0.65 mTorr) and 22.1 nm (P O2 = 1.3 mTorr), respectively. The films sputtered at higher O 2 pressure showed a preferential orientation in the <001> direction, which was associated with particle surfaces exposing highly reactive {001} facets. Films sputtered at lower O 2 pressure exhibited no, or very little, preferential grain orientation, and were associated with random distribution of particles exposing mainly the thermodynamically favorable {101} surfaces. Photocatalytic degradation measurements using methylene blue dye showed that <001> oriented films exhibited approximately 30% higher reactivity. The measured intensity dependence of the degradation rate revealed that the UV-independent rate constant was 64% higher for the <001> oriented film compared to randomly oriented films. The reaction order was also found to be higher for <001> films compared to randomly oriented films, suggesting that the <001> oriented film exposes more reactive surface sites.

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Section: Photocatalytic Measurementsmentioning

confidence: 99%

Tuning the Photocatalytic Activity of Anatase TiO2 Thin Films by Modifying the Preferred <001> Grain Orientation with Reactive DC Magnetron Sputtering

Stefanov

Österlund

2014

Coatings

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“…The measurements were carried out in a custom-built reactor wherein the concentration of the dye in the solution is measured in situ by laser colorimetry at λ = 670 nm. 29 Each experiment comprised an initial 40 minutes of adsorption, which was needed to reach adsorption-desorption equilibrium. Subsequently a black-light UV tube was used to illuminate the films (2.44 mW cm -2 at the film surface), and the dye concentration was measured in situ every 10 min for 80 min.…”

Section: Experimental Part and Methodsmentioning

confidence: 99%

Quantitative relation between photocatalytic activity and degree of 〈001〉 orientation for anatase TiO₂ thin films

et al. 2015

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Quantitative relation between photocatalytic activity and degree of#001#orientation for anatase TiO 2 thin films. We demonstrate a quantitative relation between exposed crystal surfaces and photocatalytic activity of nanocrystalline anatase TiO2. Thin films with controlled amount of <001> preferential orientation were prepared by reactive DC magnetron sputtering in Ar/O2 atmosphere with the partial O2 pressure as control parameter. The samples were characterized with X-ray diffraction, transmission electron microscopy and atomic force microscopy, from which the degree of preferential <001> orientation and exposed facets were determined by an extension of the March-Dollase model. Photocatalytic degradation of methylene blue dye shows that the photocatalytic reaction rate increases approximately with the square of the fraction of <001> oriented surfaces, with about eight times higher rate on the {001} surfaces, than on {101}, thus quantifying the effect of crystal facet abundancy on the photocatalytic activity of anatase TiO2. Journal of Materials Chemistry IntroductionThe chemical reactivity of TiO 2 is known to depend strongly on its surface structure and morphology. [1][2][3] In particular, the {001} surfaces of anatase TiO 2 have been shown to be associated with high reactivity. [4][5] Accordingly, a number of methods have been proposed to prepare chemically reactive TiO 2 materials, including e.g. laser ablation, 6 modification of surface acidity, 3 and hydrophilicity through chemical and mechano-chemical methods. 7 Recently, preparation of TiO 2 with controlled crystallographic properties, such as facet distribution and preferential orientation, has attracted considerable attention. [8][9][10][11] In particular, the study by Yang et al. of F -ion assisted shape-controlled synthesis of {001} exposed TiO 2 particles has spurred interest in this field. 12Normally anatase nanoparticles are dominated by low-energy {101} surface planes with only a fraction of {001} facets, typically about 10% of the total surface area. 13 It has been predicted that the {001} facets are much more reactive than the {101} facets due to their higher surface energy (0.9 J m -2 versus 0.44 J m -2 for {101}).14 Theoretical work has shown that water and other small molecules, such as methanol and formic acid, adsorb molecularly on {101} surfaces while dissociation is favoured on {001} surfaces. 4,5,15 Furthermore it was observed that the {001} and {101} surfaces exhibit selectivity towards oxidation and reduction reactions, respectively. 16,17 These observations suggest that it is possible to purposefully tailormake TiO 2 materials with improved reactivity. It is, however, challenging to experimentally prepare nanostructured TiO 2 with different facet distributions and quantify the facetcontrolled reactivity. Several studies have shown that reactive DC magnetron sputtering yields anatase TiO 2 films with preferential orientation along the <001> crystallographic direction. [18][19][20] Depending on the preparation conditions, this orienta...

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“…Validation experiments resulted to an average MB removal of 57.2%. The reactor performs better than other reactors in related studies [21], [24], [25] and may be considered at par with some reactors [9], but with the advantage of using a simpler immobilization method (spray coating) and the use of less expensive materials of construction (borosilicate glass) [18].…”

Section: Reactor Optimizationmentioning

confidence: 99%

Design, Mass Transfer Studies, and Optimization of an Air-Sparged Tubular Photocatalytic Reactor for the Degradation of Methylene Blue

Dalida¹,

Ramoso²

2017

IJCEA

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Abstract-An alternative process for the removal of organic pollutants in aqueous systems is photocatalysis. The challenges hindering its industrial use are electron-hole recombination and mass transfer limitations. In order to address these problems, the objective of this study is to introduce air by sparging, and design an air-sparged photocatalytic reactor using titanium dioxide immobilized on borosilicate glass. The performance of the reactor on the removal of the model pollutant, methylene blue (MB), was evaluated and compared against the reactor operated without sparging. The effect of mass transfer limitations on reactor performance was also investigated by regression using a Langmuir-type model equation. Reactor performance was optimized using Response Surface Methodology to determine the set of initial MB concentration, treatment time, initial pH, and sparging rate that would result to the highest removal of methylene blue. The sparged photocatalytic reactor was able to degrade 57% MB in 2 hours, an improvement of 40% compared to no sparging. Mass transfer limitation studies showed that the reactor operates near the reaction-limited regime, and that the extent of mass transfer limitation effects was reduced. The set of parameters that maximizes methylene blue removal were 2.0 ppm MB, 120 minutes treatment time, pH 9.95 and 2.0 L/min sparging rate, with a predicted removal of 55.5%. Validation experiments resulted to 57.2% MB removal, and that the present reactor is comparable to similar reactors in literature, but with the advantage of using less expensive materials of construction and simpler immobilization technique.Index Terms-Photocatalysis, response surface methodology, tubular photocatalytic reactor, wastewater treatment.

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Novel integrated reactor for evaluation of activity of supported photocatalytic thin films: Case of methylene blue degradation on TiO2 and nickel modified TiO2 under UV and visible light

Cited by 22 publications

References 21 publications

Tuning the Photocatalytic Activity of Anatase TiO2 Thin Films by Modifying the Preferred <001> Grain Orientation with Reactive DC Magnetron Sputtering

Tuning the Photocatalytic Activity of Anatase TiO2 Thin Films by Modifying the Preferred <001> Grain Orientation with Reactive DC Magnetron Sputtering

Quantitative relation between photocatalytic activity and degree of 〈001〉 orientation for anatase TiO₂ thin films

Design, Mass Transfer Studies, and Optimization of an Air-Sparged Tubular Photocatalytic Reactor for the Degradation of Methylene Blue

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Novel integrated reactor for evaluation of activity of supported photocatalytic thin films: Case of methylene blue degradation on TiO2 and nickel modified TiO2 under UV and visible light

Cited by 22 publications

References 21 publications

Tuning the Photocatalytic Activity of Anatase TiO2 Thin Films by Modifying the Preferred <001> Grain Orientation with Reactive DC Magnetron Sputtering

Tuning the Photocatalytic Activity of Anatase TiO2 Thin Films by Modifying the Preferred <001> Grain Orientation with Reactive DC Magnetron Sputtering

Quantitative relation between photocatalytic activity and degree of 〈001〉 orientation for anatase TiO2 thin films

Design, Mass Transfer Studies, and Optimization of an Air-Sparged Tubular Photocatalytic Reactor for the Degradation of Methylene Blue

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Quantitative relation between photocatalytic activity and degree of 〈001〉 orientation for anatase TiO₂ thin films