Improved stability in SBA-15 mesoporous materials as catalysts for photo-degradation processes (original) (raw)
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Microporous and Mesoporous Materials, 2017
Mesoporous silica, SBA-15, decorated with different amounts of TiO 2 (anatase) were prepared by a sol-gel method followed by hydrothermal treatment and calcination, in the presence of a soft template, copolymer Pluronic 123. Tetraethyl orthosilicate (TEOS) was used as the SiO 2 precursor and commercially available TiO 2 anatase nanoparticles as the supported photocatalyst. The materials were characterized by transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDS), N 2 adsorptiondesorption isotherms, raman spectroscopy, ground state diffuse reflectance (GSDR), laser induced luminescence (LIL) and X-ray photoelectron spectroscopy (XPS). The zeta potentials of the pure SBA-15, TiO 2 /SBA-15 substrate and the commercial anatase sample were monitored through a complete range of pH values. All the nanomaterials developed in this work were studied in terms of their photoactivity in the UV range and in the visible range, separately. In the first case, hydroxyl radicals (OH) were confirmed to be the key active oxidizers in the photodegradation of the pesticide amicarbazone in aqueous medium. On the other hand, in the visible range, and following a dye sensitization process via a fluorescent rhodamine-like dye, two different mechanisms could be identified for the formation of the superoxide radical anion, O 2 À .
Chemical Engineering Journal, 2011
Thick-walled hexagonally ordered Cobalt and titanium loaded SBA-15 mesoporous photocatalysts were prepared by impregnating the metal precursor solution on the hydrothermally stable support. The catalysts were analyzed using various spectroscopic and diffraction techniques. XRD measurements revealed that Co exists as its spinel structure Co 3 O 4 and Ti is present in the anatase TiO 2 phase. FTIR showed the absorption bands of Co 3 O 4 around 667 and 565 cm −1 . The visible light absorbance of the photocatalytic systems was studied by Diffuse Reflectance Ultraviolet-Visible spectroscopy (UV-vis DRS) measurements. Systems exhibited fairly good performance as photocatalysts for pollutant degradation under visible light. SBA-15 support was helpful in the easy separation of catalysts after the completion of the degradation. In the case of cobalt loaded SBA-15, activity is found to be maximum when the cobalt loading is 40% whereas 50% Ti loaded SBA-15 is found to be the most active among the prepared systems for the degradation of the dye pollutant methylene blue (MB).
A photo-catalyst of mesoporous silicate SBA-15 doped with 15%MoO 3 was synthesized by modified sol–gel process and then characterized by SBET, XRD, HRTEM/EDX, TGA and optical techniques. The photo-catalytic performances of 15%Mo/SBA-15 were tested in the photo-remediation of wastewater composed of multi-organic pollutants (i.e., aromatics, phenols, and dyes) at different light sources of visible (400 nm), UVB (316 nm)and UVC (254 nm) irradiation. The photo-catalytic activities of the 15%Mo/SBA-15 were considerably greater under UVC irradiation, which is coincident with 15%Mo/SBA-15 calculated band gap of 3.5 eV. Further, wastewater treatment rate was ranked in the order of aromatic > phenolic > dyes with the rate of 95%, 69%, and 14%, respectively after 120 min UVC irradiation time. A statistical analysis, using both parametric (one way ANOVA) and nonparametric (Kruskal-Wallis) methodologies, were developed to validate the experimental comparison between neat SBA-15 and 15%Mo/SBA-15 based on structural properties, light intensity and the type of organic contaminants are the key factors influencing the photo-catalytic degradation rate. The kinetic rate of the was-tewater photo-catalytic remediation was found to be ranked in the order of benzene > anthracene > pyrene > naphthalene within aromatic contaminants, hydroxyphenyl ≈ chlorophenols > phenol within the phenolic group, and no significant difference between methyl orange and methyl red within dyes contaminants over 15%Mo/SBA-15. Results suggested that the developed 15%Mo/SBA-15 could be used as efficient photo-catalysts for the treatment of petroleum and petrochemical wastewater with aromatic and phenolic hazardous, but not efficient for the treatment of textile wastewater pollutants.
MCM-41-based materials for the photo-catalytic degradation of Acid Orange 7
Catalysis Today, 2011
MCM-41 materials were modified with Cr, Fe, Co and Ti and characterized by ICP, XRD, N 2 adsorption, UV-Vis DRS and TPR. Their photo-catalytic activity was evaluated for the degradation of Acid Orange 7 (AO7) in aqueous suspensions irradiated by artificial UV-Vis and visible light. The results showed that the Cr-modified catalysts exhibited the highest activity under visible light. The presence of Cr 6+ highly dispersed on the internal surface of the MCM-41 structure would have a significant influence on the photo-activity. Thus, the lack of a notable increment in the activity when the Cr loading was duplicated is probably due to the increased presence of inactive Cr 3+ species. Upon the TiO 2 loading, an increase in the degradation was not observed. It is suggested that the Cr 3+ species, as Cr 2 O 3 clusters and/or ␣-Cr 2 O 3 nano-particles, could avoid the desired heterojunction between Cr 6+ and titania species.
RSC Advances, 2019
A dark-coloured effluent called "spent wash" is generated as an unwanted product in sugarcane-based alcohol distilleries. Most distilleries discharge this effluent into soil or water without any treatment, causing water and soil pollution. Herein, we report chromium-doped TiO 2 (Cr-TiO 2) as a photocatalyst for the degradation of spent wash colour under natural sunlight. Cr-doped TiO 2 nanoparticles were prepared using an aqueous titanium peroxide-based sol-gel method with titanium isopropoxide as the Ti precursor and chromium nitrate as the Cr precursor. To observe the effect of dopant on sol-gel behaviour and physicochemical properties, the Cr concentration was varied in the range 0.5-5 wt%. The crystallization temperature and time were optimized to obtain the required phase of Cr-TiO 2. The physicochemical characteristics of the Cr-doped TiO 2 catalyst were determined using X-ray diffraction, FE-SEM, FETEM, TG, XPS, the Brunauer-Emmett-Teller (BET) method, FT-IR, Raman, PL, ICP-MS, and UV visible spectroscopy. A shift in the absorption edge of TiO 2 by doping with chromium suggested an increase in visible light absorption due to a decrease in the effective band gap. The application potential of the Cr-TiO 2 catalyst was studied in the degradation of sugar-based alcohol distillery waste under natural sunlight, and the results were compared with those of undoped TiO 2 and Degussa P25 TiO 2. Degradation of the spent wash solution was monitored using UV-visible, gel permeation chromatography (GPC), and QTOF LC-MS. GPC and LC-MS showed significant changes in the molecular weight of spent wash colour-forming compounds due to the degradation reaction. QTOF LC-MS analysis suggested that acids, alcohols, glucosides, ketones, lipids, peptides, and metabolites were oxidized to low-molecular-weight counterparts. From the results, 5% Cr-TiO 2 showed the highest degradation rate among all Cr-TiO 2 samples, undoped TiO 2 , and Degussa P25 TiO 2 under identical reaction conditions, with nearly 68-70% degradation achieved in 5 h.
2016
Heterogeneous photocatalysis is a promising technology especially for environmental remediation. Despite more than a decade of worldwide research in developing photocatalytic efficiency improving techniques, many questions regarding the large scale application of photocatalytic reactors still remain unanswered. Recently, improving the photocatalytic efficiency has gained scientific attention because it might lead to more economical and robust photocatalytic operation for environmental remediation. In this review, fundamental and comprehensive assessments of the photocatalytic concepts and their applications for environmental remediation are reviewed. The existing challenges and strategies to improve the photocatalytic efficiency are discussed. Further, recent developments and future research prospects on photocatalytic systems for environmental applications are also addressed.
Materials, 2019
Titanium dioxide materials were synthesized using two different methods. The samples were characterized by X-ray diffraction (XRD), UV-Visible diffusion reflectance spectroscopy (UV-Vis DR), Raman spectroscopy, N 2 adsorption/desorption, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron spectroscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Although both kind of materials were found to have mesoporous structure and anatase crystalline phase, one of them was obtained from a synthesis method that does not involve the use of surfactants, and therefore, does not require calcination at high temperatures. This implies that the synthesized solid was self-doped with carbon species, coming only from the same source used for titanium. Then, the relationship between the presence of these species, the final calcination temperature, and the photocatalytic activity of the solids was studied in terms of the degradation and mineralization of an Acid Orange 7 aqueous solution, under visible radiation. A photosensitizing effect caused by the non-metal presence, that allows the solid to extend its absorption range, was found. Hence, a novel route to prepare C-modified photoactive mesoporous TiO 2 , simpler and cheaper, where neither a template nor an external carbon source is used, could be performed.
Photocatalysis: Past, Present and Future Trends for Remediation of Wastewater
2022
The current paper examines the use of Photocatalysis in various wastewater treatment applications, beginning with a brief overview of how industrialization is causing various water threats and how wastewater treatment processes, particularly Advanced Oxidation Processes (AOPs), have improved in recent years. Then, we go over the current status of photocatalysis in wastewater clean up,as well as the numerous hurdles that are encountered along the way. The applications of photo catalytic technology in waste water treatment are highlighted ,as well as the most recent efforts to improve photocatalytic materials. A brief explaination of photocatalytic reactor design and system evaluation is also included. Finally, the tactics for boosting research outputs and the future prospects of photocatalysis are discussed.