Abstract

In this paper, nanostructured TiO2 film was prepared by the by sol-gel process and dip-coating technique with titanium tetraisopropoxide as a precursor. After heat treatment at 550 °C, the deposited film was characterized by means of micro-Raman spectroscopy and atomic force microscopy (AFM). It was found that the TiO2 film consisted of only the TiO2 anatase phase and showed a granular microstructure. Photocatalytic degradation of azithromycin by using sol-gel nanostructured TiO2 film was studied to define the most effective degradation process for potential use in wastewater treatment. Different factors were evaluated during photocatalysis, such as pH (3, 7, and 10), water matrix (ultrapure water and synthetic municipal waste water effluent), influence of another pharmaceutically active compound (sulfamethoxazole, one of the most often detected pharmaceutic compounds in waste waters), and radiation sources (low pressure ultraviolet (UV) mercury lamps with a UV-A and UV-C range; a light-emitting diode (LED) lamp with a radiation peak at 365 nm). The most effective degradation process was achieved with the UV-C irradiation source in matrices at pH 10. The water matrix had little effect on the photocatalytic degradation rates of azithromycin. The presence of sulfamethoxazole in the water matrix decreased the degradation rate of azithromycin, however, only in matrices with a pH level adjusted to 10. During the experiments, five azithromycin degradation products were identified and none of them showed toxic properties, suggesting effective removal of azithromycin. LED 365 nm as the irradiation source was not as effective as the UV-C lamp. Nevertheless, considering the cost, energy efficiency, and environmental aspects of the irradiation source, the LED lamp could be a “real-life” alternative.

Highlights

  • The presence of pharmaceuticals in the environment has been the focus of scientific research world-wide for several decades and the issue it poses for the environment is well established.Pharmaceuticals may reach the environment via different pathways, but wastewater treatment plants are considered to be prominent [1]

  • None of the investigated samples showed any toxicity, which that the newly formed degradation products are not toxic. These results show that photocatalytic proves that the newly formed degradation products are not toxic. These results show that photocatalytic degradation is an efficient way of removing azithromycin from the waste waters without producing new compounds which are toxic

  • The purpose of this research was to investigate the photocatalytic degradation of azithromycin under real life conditions to prove that photocatalytic oxidation is an option for waste water purification

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Summary

Introduction

The presence of pharmaceuticals in the environment has been the focus of scientific research world-wide for several decades and the issue it poses for the environment is well established.Pharmaceuticals may reach the environment via different pathways, but wastewater treatment plants are considered to be prominent [1]. Materials 2019, 12, 873 and potential transformation products These compounds reach the environment without being decomposed during treatment. Once they reach the environment, they may have possible negative effects on all types of organisms. They influence organisms they encounter and the resulting consequences are still under investigation. To control their levels in the environment, and in that way, minimize possible negative effects, legal definitions of their concentrations in the environment are required. Aggravating circumstances exist, including the lack of data on the chronic toxicity of such compounds, and ecotoxicological data for mixtures of pharmaceuticals, their metabolites, and transformation products [2]. The combination of all the mentioned properties can result in an imbalance in the complete ecosystem [3]

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