TiO2 and N-TiO2 Sepiolite and Zeolite Composites for Photocatalytic Removal of Ofloxacin from Polluted Water

Abstract

TiO2 sepiolite and zeolite composites, as well the corresponding N-doped composites, synthesized through a sol–gel method, were tested for the photocatalytic degradation of a widespread fluoroquinolone antibiotic (ofloxacin) under environmental conditions. The catalysts were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS) analyses. A complete drug degradation occurred in 10–15 min in the presence of both TiO2 sepiolite and zeolite catalysts, and in 20–30 min with the N-doped ones. Sepiolite proved to be a better TiO2 support compared to the most common zeolite both in terms of adsorption capacity and photocatalytic efficiency in pollutants degradation. The influence of nitrogen doping (red shift from 3.2 to 3.0 eV) was also investigated. Although it was blurred by a marked increase of the particle dimension and thus a decrease of the specific surface area of the doped catalysts, it allowed a faster drug removal than direct photolysis. The photochemical paths and photoproducts were investigated, too.

Improving the photocatalytic activity of nitrogen-doped surface defect TiO2-x nanobelts for degradation of organic pollutants

“…The N2p form impurity states above the valance band (VB), which narrows the band gap energy of TiO 2 . According to literature reports, 37,38 Ti 4+ is reduced to Ti 3+ and oxygen vacancies can significantly prolong the lifetime of photo-electrons and restrain the recombination of photogenerated electrons and holes. The holes of the VB react with hydroxyl groups (OH − ) to generate •OH radicals.…”

Water Depollution and Photo-Detoxification by Means of TiO2: Fluoroquinolone Antibiotics as a Case Study

“…The sharp increase of papers published in the field is due to the solid evidence of the mechanism and the excellent properties of this material that has a minimal (photo)toxicity, good long-term stability, is low-cost and requires virtually no treatment prior to application. It is true that some increase in efficiency could be obtained either by using a single crystal phase (the commercial material is a mixture of anatase, rutile and brookite) [49][50][51], by controlling the micro-structure or the organization of the semiconductor [52], or through either metal or non-metal ion doping that allows fraction of solar energy absorbed toward the visible to be extend, although this reduces the potentially accessible range of oxidizable molecules [52,53]. The overall efficacy of these changes is still relatively limited and the first experiment carried out with commercial titania powder gives a satisfactory estimate of the final result [49].…”

A High-Efficiency TiO2/ZnO Nano-Film with Surface Oxygen Vacancies for Dye Degradation

“…Indeed, the limited charge transfer and high electron-hole recombination are the main factors hindering the photocatalytic performance of TiO 2 [7]. To accelerate electron transport and reduce charge recombination of TiO 2 , many ways have been designed and employed, such as doping with transition metal or non-metal [8], increasing surface area [9], and constructing a proper heterostructure [10], etc. Among these different methods, constructing a proper heterostructure is one of the most effective strategies to improve the photocatalytic ability of TiO 2 by accelerating the transfer of photo-generated e-h pairs at the interface between various semiconductor materials [11][12][13].…”