Alumina coating with TiO₂and its effect on catalytic photodegradation of phenol andp-cresol

Abstract

BACKGROUND This study is focused on the peptization of Boehmite and titanium alkoxide (modified sol–gel method) to obtain Al2O3–TiO2 mixed oxides taking advantage of the physicochemical properties of TiO2 and Al2O3. TiO2 is an important semiconductor and the most active photocatalyst. Al2O3 is an insulator with high surface area and thermal, chemical and mechanical resistance. It is possible to produce high surface area materials, where TiO2 is dispersed on the alumina surface for photodegradation of pollutants. RESULTS γ‐Al2O3–TiO2 (5, 10 and 15 wt% TiO2) mixed oxides presented stabilization of the anatase phase. Rietveld studies showed incorporation of the Al3+ into the TiO2 anatase and Ti4+ into the Al2O3. They exhibit higher specific surface area than pure TiO2. The TiO2‐coated alumina surface with small TiO2 particles produced a large number of active sites on the surface. The sample with 15 wt% of TiO2 presented the highest photodegradation of p‐cresol and phenol. CONCLUSION The addition of TiO2 to the alumina improved the photoactivity of pure TiO2 producing materials with higher surface area covered with TiO2. Alumina delayed the recombination of photogenerated electron–hole pairs favoring the formation of highly reactive •OH radicals. The photodegradation of p‐cresol and phenols increased with TiO2 loading increase. © 2016 Society of Chemical Industry

Sunlight photoactivity of rice husks-derived biogenic silica

“…However, it has important scale-up limitations such as the high and pH-dependent recombination rate, a low absorption of solar light, and the low to moderate surface area of most commercial TiO 2 -based photocatalysts, which limits their application to low effluent volumes and low pollutants concentration [3,4]. It has been extensively reported than most of these limitations can be overcome by using various co-supports such as alumina [5], silica [6,7], and activated carbon [8][9][10].…”

Multistimuli Activation of TiO2/α-Alumina Membranes for Degradation of Methylene Blue

“…Indeed, the absorption of substrate molecules will be promoted by the alumina porous support and by the forced permeation of reagents through the catalytic membrane pores . The efficiency of the supported-TiO 2 photocatalyst could also be enhanced, since alumina is able to trap the photogenerated (e – ) and (h + ) charges, delaying their recombination. ,, Moreover, it has been proved that, by extending the interfacial contact surface between the TiO 2 semiconductor and Al 2 O 3 support, important surface defects are created at the alumina–titania interface, which act as active sites for photodegradation …”

“…In recent years, semiconductor photocatalytic processes have been shown to have great potential as a low-cost, environmentally friendly, and sustainable technology for wastewater treatment and environmental remediation. − Compared with other materials, titanium dioxide (TiO 2 )-based photocatalysts are the most attractive due to the multiple advantages that they display: (i) high efficiency, (ii) structural stability, (iii) nontoxicity, and (iv) ready availability. , Their ability to remove refractory organic pollutants and microorganisms in water by photooxidative processes has been widely demonstrated by using both artificial and natural lights. , The main research efforts have been addressed to modify the TiO 2 structural and electronic properties, with the aim of improving the photocatalyst efficiency and extending their photoresponse into the visible region. The main strategies adopted to reach these aims comprise impurity-doping, − dye anchoring, − design of TiO 2 nanohybrids, or defect-engineered (including Ti 3+ self-doped) nanophases. − The use of charge transfer catalysts (CTCs), such as Al 2 O 3 , to prepare TiO 2 -based photocatalysts is an alternative way of improving the photocatalytic activities. − These composite binary oxides frequently exhibit unexpected properties derived from a synergistic interaction between the two components. Indeed, Al 2 O 3 hosting materials are proved to trap the photogenerated charges, delaying their recombination, and to enhance the adsorption ability of the photocatalyst for target molecules.…”

“…This strategy would allow for maintaining a high surface area to volume ratio of the catalyst, thus maximizing the number of highly reactive surface sites. Moreover, by improving the surface contact area between the TiO 2 semiconductor and the Al 2 O 3 surface a major number of defects can be created at the interface, which would act as active sites for photodegradation. , Furthermore, higher permeate fluxes are also expected for these modified membranes, due to the reduced thickness of the TiO 2 top layer and the photoinduced hydrophilic effect …”

Advanced Ceramics in Radical Filtration: Tio2 Layer Thickness Effect on the Photocatalytic Membrane Performance

“…They supported the idea that the coating blocks the transfer of both photo-generated holes and electrons by the reduction of photocatalytic oxidation and photocatalytic reduction. Gomez et al [42] created coatings with a mixture of 𝛼-alumina and TiO 2 . Their study concluded that the presence of Al 2 O 3 decreases the electron-hole recombination as it acts as a charge transfer catalyst.…”