Au/Ti Synergistically Modified Supports Based on SiO2 with Different Pore Geometries and Architectures

Abstract

New photocatalysts were obtained by immobilization of titanium and gold species on zeolite Y, hierarchical zeolite Y, MCM-48 and KIT-6 supports with microporous, hierarchical and mesoporous cubic structure. The obtained samples were characterized by X-ray diffraction (XRD), N2-physisorption, scanning and transmission electron microscopy (SEM/TEM), diffuse reflectance UV–Vis spectroscopy (DRUV-Vis), X-ray photoelectron spectroscopy (XPS), Raman and photoluminescence spectroscopy. The photocatalytic properties were evaluated in degradation of amoxicillin (AMX) from water, under UV (254 nm) and visible light (532 nm) irradiation. The higher degradation efficiency and best apparent rate constant were obtained under UV irradiation for Au-TiO2-KIT-6, while in the visible condition for the Au-TiO2-MCM-48 sample containing anatase, rutile and the greatest percent of Au metallic clusters were found (evidenced by XPS). Although significant values of amoxicillin degradation were obtained, total mineralization was not achieved. These results were explained by different reaction mechanisms, in which Au species act as e− trap in UV and e− generator in visible light.

Co- and Ni-Doped TiO2 Nanoparticles Supported on Zeolite Y with Photocatalytic Properties

“…These materials have significant advantages in reactions involving large molecules by coupling the native micropores with an intracrystalline mesoporous network. Higher adsorption capacity and degradation efficiency of amoxicillin were obtained for Au-Ti [7] and Fe-Ti [8] bimetallic photocatalysts supported on hierarchical zeolite Y photocatalysts. All zeolite supports are not photoactive, so they were activated by the incorporation of semiconductors and metal nanoparticles.…”

“…Unfortunately, the micropores from zeolites and active sites from the surface are less accessible to organic pollutants due to the limitations of mass transport. Furthermore, materials with a mesoporous structure are widely used as supports in the synthesis of photocatalysts because of their highly ordered mesoporous channels and large surface areas [5][6][7]. The solution to keep the properties of zeolites, along with the advantage of mass transfer through mesopores, seems to be hierarchical zeolites.…”

“…However, TiO 2 is a wide-band-gap semiconductor (~3.2 eV) and has a high recombination rate for electron-hole pairs with limited practical utility [12,13]. Recently, there has been increased interest in the synthesis of nanocomposite materials as photocatalysts that are more efficient and active under visible light irradiation by doping TiO 2 with noble metals [7,14,15] and transition metal semiconductors [8,[16][17][18][19]. Increasing catalytic activity with transition metals is an alternative to highly expensive noble metals.…”

Effect of the Modification of Catalysts on the Catalytic Performance

“…The superior photocatalytic activity of CuLTO-800R was attributed to its narrow band gap and photogenerated-carriers separation. Petcu et al [6] presented the synthesis and characterization of new photocatalysts obtained through the immobilization of titanium and gold on the supports with various porous structures (micropores-zeolite Y, micro and mesopores-hierarchical zeolite Y, smaller mesopores-MCM-48 and larger mesopores-KIT-6). The effects of porous structure and surface properties on TiO 2 dispersion, crystal structure, the nature of the interaction between support-titanium species and Au-TiO 2 , respectively, were studied.…”

Effects of Aluminosilicate Gel Treatment and TiO2 Loading on Photocatalytic Properties of Au–TiO2/Zeolite Y

“…The narrowing of the energy band gap was achieved by TiO 2 doping with various metals or nonmetal species [ 13 , 14 , 15 , 16 , 17 , 18 ]. A method to diminish agglomerations is the immobilization of TiO 2 nanoparticles on a support framework, such as zeolites [ 19 , 20 , 21 , 22 ]. In this case, the surface chemistry of the support plays a decisive role in photocatalytic activity and stability [ 23 ].…”