Abstract
Pharmaceuticals, especially antibiotics, constitute an important group of aquatic contaminants given their environmental impact. Specifically, tetracycline antibiotics (TCs) are produced in great amounts for the treatment of bacterial infections in both human and veterinary medicine. Several studies have shown that, among all antibiotics, oxytetracycline hydrochloride (OTC HCl) is one of the most frequently detected TCs in soil and surface water. The results of the photocatalytic degradation of OTC HCL in aqueous suspensions (30 mg·L−1) of 0.5 wt.% cobalt-doped TiO2 catalysts are reported in this study. The heterogeneous Co-TiO2 photocatalysts were synthesized by two different solvothermal methods. Evonik Degussa Aevoxide P25 and self-prepared TiO2 modified by the same methods were used for comparison. The synthesized photocatalysts were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), UV/vis diffuse reflectance spectroscopy (DRS), and N2 adsorption (BET) for specific surface area determination. The XRD and Raman results suggest that Ti4+ was substituted by Co2+ in the TiO2 crystal structure. Uv/visible spectroscopy of Co-TiO2-R showed a substantial redshift in comparison with bare TiO2-R. The photocatalytic performance of the prepared photocatalysts in OTC HCL degradation was investigated employing Uv/vis spectroscopy and high-performance liquid chromatography (HPLC). The observed initial reaction rate over Co-TiO2-R was higher compared with that of Co-TiO2-HT, self-prepared TiO2, and the commercial P25. The enhanced photocatalytic activity was attributed to the high surface area (153 m2·g−1) along with the impurity levels within the band gap (2.93 eV), promoting the charge separation and improving the charge transfer ability. From these experimental results, it can be concluded that Co-doping under reflux demonstrates better photocatalytic performances than with the hydrothermal treatment.
Highlights
The growing demand for clean water sources has become an important issue worldwide owing to increasing water pollution by, for example, pharmaceuticals, personal care products, and endocrineMolecules 2020, 25, 249; doi:10.3390/molecules25020249 www.mdpi.com/journal/moleculesMolecules 2020, 25, 249 disruptors
Among a wide variety of pharmaceutical compounds, antibiotics, owing to their extensive use in human and veterinary medicine, may cause environmental impacts, disturbing the function of the ecosystem by developing antibiotic-resistant pathogens that are of potential risk for human health after incorporation with drinking water, and vegetables or fruits irrigated with contaminated water [1,2,3]
The concentrations of the antibiotics released from the environmental matrix to aquatic systems are extremely low, oxytetracycline hydrochloride (OTC HCl) recognized as an emerging pollutant may cause serious risks to human health and ecosystems [6]
Summary
The growing demand for clean water sources has become an important issue worldwide owing to increasing water pollution by, for example, pharmaceuticals, personal care products, and endocrineMolecules 2020, 25, 249; doi:10.3390/molecules25020249 www.mdpi.com/journal/moleculesMolecules 2020, 25, 249 disruptors. Among a wide variety of pharmaceutical compounds, antibiotics, owing to their extensive use in human and veterinary medicine, may cause environmental impacts, disturbing the function of the ecosystem by developing antibiotic-resistant pathogens that are of potential risk for human health after incorporation with drinking water, and vegetables or fruits irrigated with contaminated water [1,2,3]. The concentrations of the antibiotics released from the environmental matrix to aquatic systems are extremely low (μg·L−1 to mg·L−1 ), OTC HCl recognized as an emerging pollutant may cause serious risks to human health and ecosystems [6]. Owing to its chemical stability and antibiotic property, residues of OTC HCl released in the aquatic environment cannot be removed by conventional water treatment processes [7]. There are numerous limitations such as the formation of byproducts, selective functional, photosensitive groups, and contact time [3]
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