1,720,996 research outputs found
Degradation of 4-chlorophenol and NO x Using Ultrasonically Synthesized TiO2 Loaded Graphene Oxide Photocatalysts
No full textTiO2, GO–TiO2, Pt–GO–TiO2 were synthesized using an ultrasound-assisted technique. The synthesized photocatalysts were characterized using XRD, UV-Vis, FTIR and TEM-EDX instruments. The photocatalytic activities of these catalysts were compared using the degradation of 4-chlorophenol (4-CP) in aqueous solutions. Pt–GO–TiO2 showed higher rate of degradation of 4-CP than that of bare TiO2. Doping of TiO2 with Pt (0.4 wt%) exhibited total degradation of 4-CP in 1 h under light irradiation. A similar trend was observed with mineralization of 4-CP using different catalysts which was monitored by total organic carbon (TOC) analysis. Among different solution pH, pH 6 showed high efficiency for the degradation of 4-CP. A combined method of ultrasound and photocatalysis was also investigated for the effective degradation of 4-CP. High frequency (215 kHz) ultrasound exhibited higher degradation of 4-CP than low frequency (20 kHz) of ultrasound. There was no synergistic effect of photocatalysis combined with ultrasound method but an additive effect was observed. Gas phase degradation of NO x was also carried out using the above catalysts and the results revealed that GO–TiO2 was an excellent catalyst for the total decomposition of toxic NO x gas in a short period of time without using Pt. GO was proved to be a useful support for photocatalysts effective for both gas phase as well as liquid phase reactions and, GO–TiO2 can be a viable catalyst for gas phase decomposition of air-pollutants
Sonophotocatalytic Degradation of 4-chlorophenol using Bi2O3-TiZrO4 as a Visible Light Driven Photocatalyst
No full textSonophotocatalytic degradation of 4-chlorophenol using Bi2O3/TiZrO4 as a visible light responsive photocatalyst
No full textThe oxidative degradation of 4-chlorophenol (4-CP) by sonolytic, photocatalytic and sonophotocatalytic processes was studied in aqueous solutions using Bi2O3/TiZrO4 as a visible light driven photocatalyst and with 20kHz ultrasound. The results reveal that Bi2O3/TiZrO4 is an efficient photocatalyst capable of degrading 4-CP by both photocatalytic and sonophotocatalytic processes. During the sonolysis of 4-CP solutions, HPLC results showed the formation of a number of intermediate products, whereas, no such intermediates were formed during the sonophotocatalytic degradation of 4-CP. TOC results showed rapid mineralization of 4-CP during the sonophotocatalytic degradation process, relative to that observed with sonolysis alone. The results reveal a clear advantage in using a coupled method for the oxidation of 4-CP and a cumulative effect was observed. Further, the solution pH had no specific influence on the sonophotocatalytic degradation of 4-CP, unlike the situation for sonolysis alone where the degradation rate decreased as the pH was raised from acidic to basic conditions. The combined sonophotocatalytic degradation process was found to be simple to apply and has the potential to be a powerful method for the remediation of organic contaminants present in water and wastewater
Graphene oxide based Pt–TiO2 photocatalyst: Ultrasound assisted synthesis, characterization and catalytic efficiency
No full textAn ultrasound-assisted method was used for synthesizing nanosized Pt–graphene oxide (GO)–TiO2 photocatalyst.
The Pt–GO–TiO2 nanoparticles were characterized by diffused reflectance spectroscopy, X-ray diffraction, N2 BET adsorption–desorption measurements, atomic force microscopy and transmission
electron microscopy. The photocatalytic and sonophotocatalytic degradation of a commonly used anionic surfactant, dodecylbenzenesulfonate (DBS), in aqueous solution was carried out using Pt–GO–TiO2 nanoparticles in order to evaluate the photocatalytic efficiency. For comparison purpose, sonolytic degradation
of DBS was carried out. The Pt–GO–TiO2 catalyst degraded DBS at a higher rate than P–25 (TiO2), prepared TiO2 or GO–TiO2 photocatalysts. The mineralization of DBS was enhanced by a factor of 3 using
Pt–GO–TiO2 compared to the P–25 (TiO2). In the presence of GO, an enhanced rate of DBS oxidation was observed and, when doped with platinum, mineralization of DBS was further enhanced. The Pt–GO–TiO2 catalyst also showed a considerable amount of degradation of DBS under visible light irradiation. The initial solution pH had an effect on the rate of photocatalytic oxidation of DBS, whereas no such effect of initial pH was observed in the sonochemical or sonophotocatalytic oxidation of DBS. The intermediate products formed during the degradation of DBS were monitored using electrospray mass spectrometry.
The ability of GO to serve as a solid support to anchor platinum particles on GO–TiO2 is useful in developing
new photocatalysts
Efficient photocatalytic degradation of organics present in gas and liquid phases using Pt-TiO2/Zeolite (H-ZSM)
No full textTiO2-encapsulated H-ZSM photocatalysts were prepared by physical mixing of TiO2 and zeolites. Pt was immobilized on the surface of the TiO2-encapsulated zeolite (H-ZSM) catalysts by a simple photochemical reduction method. Different weight ratios of both TiO2 and Pt were hybridized with H-ZSM and the catalytic performance of the prepared catalysts was investigated for 2-propanol oxidation in liquid phase and acetaldehyde in gas phase reaction. Around 5e10 wt% TiO2-encapsulated H-ZSM catalysts was found to be optimal amount for the effective oxidation of the organics. Prior to light irradiation, Pt-TiO2-H-ZSM showed considerable amount of catalytic degradation of 2-propanol in the dark, forming acetone as an intermediate. In this study, Pt has played a major and important role on the total oxidation of 2- propanol as well as acetaldehyde. As a result, no residual organics were present in the pores of the zeolites. The catalysts could be reused more than three times without losing their catalytic activity in both phases. The Pt-TiO2-H-ZSM photocatalysts could overcome the problem of strong adsorption of organics in the zeolite pores (after the reaction). Thus, Pt-TiO2-H-ZSM can be used as a potential catalyst for both liquid and gas phase oxidation of organic pollutants
Ultrasonic enhancement of the acidity, surface area and free fatty acids esterification catalytic activity of sulphated ZrO2-TiO2 systems
Full text linkDifferent samples of sulphated zirconia and mixed zirconia/ titania (SO4 2-/ZrO2 and SO42- /80%ZrO2-20%TiO2), were prepared with traditional and ultrasound (US) assisted sol-gel synthesis and tested in the free fatty acids esterification. The catalysts were characterized through acid sites quantification by ion exchange, specific surface area and porosity measurements (N2 adsorption at 77 K), XRD, XPS and FT-IR spectroscopy. SEM-EDX and TEM analyses were also used to investigate the morphology of the samples. The results of this study demonstrate the possibility of increasing the acidity and the surface area of sulphated zirconia through the addition of TiO2 and tune the same properties with the continuous or pulsed US. It is also demonstrated that it is necessary to combine specific values of both acidity and surface area and which type of active sites are essential to obtain better catalytic performances in the free fatty acids esterification
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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