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.
Highlights
Water quality and water re-use are two emerging issues related to the most important natural resource on which the entire life of the planet depends
The synthesized composites were characterized by means of X-ray diffraction (XRD), BET, scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS) analyses
We report a critical comparison among various TiO2 and N-doped TiO2 sepiolite and zeolite composites for the photocatalytic degradation of one of the most used human antibiotics
Summary
Water quality and water re-use are two emerging issues related to the most important natural resource on which the entire life of the planet depends. It has been established that the conventional wastewater treatment plants are not suitable for the quantitative abatement of a wide range of chemicals, the so-called Contaminants of Emerging Concern (CEC), which are re-entering the bodies of water, even though at very low concentration levels. The removal of CEC, especially pharmaceuticals and personal care products (PPCPs) from waters is an urgent task. These have been detected worldwide in surface waters, drinking waters, wastewater effluents, and soils. Some drugs have been recently integrated in the list of priority of pollutants by water legislation [1,2,3,4], most of them are not regularly monitored, and the potentially negative environmental implications due to long-time exposure at trace levels cannot be ignored, as recently demonstrated by many studies [4,5]. Antibiotics pose a serious threat because they contribute to the emergence of Materials 2020, 13, 537; doi:10.3390/ma13030537 www.mdpi.com/journal/materials
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