Effect of Nitrate on the Semiconductor-Based Photocatalytic Degradation of Azithromycin

The efficacy of photocatalytic degradation can be influenced by light intensity, matrix elements, and ambient conditions. Matrices such as metal ions, humic acid, and sodium bicarbonate can decrease optimal reaction rates and change photodegradation products. Exogenous substances such as nutrients, dissolved organic matter, and absorption coefficients can significantly affect semiconductor-based photocatalytic degradation of pollutants. However, research on nutrient effects on macrolide antibiotic degradation is limited. In the present study, a titanium dioxide (TiO2) photocatalyst was used for photocatalytic degradation of azithromycin (AZC). UV-vis diffuse reflectance spectroscopy and X-ray diffraction (XRD) were used to characterize the photocatalyst. All of the diffraction peaks were attributed to the anatase phase TiO2 structure, possessing a compatible bandgap for study under ultraviolet irradiation. Photocatalysis of AZC with and without UV light was carried out, and maximum degradation of more than 91% was observed under UV light+TiO2. Further, the effect of nutrients was assessed, indicating the optimal influence at pH 9 and overall degradation efficiency in the following order: NO3<control<NO2<NH3<M–3 (matrix of nutrients). The sulphuric acid-colorimetric method was used to monitor the concentration of AZC. Beyond that, toxicity bioassay showed that no sample exhibited toxicity, indicating that this technique is an effective method of eliminating AZC from wastewater without generating new toxic byproducts. Overall, this work demonstrates an efficient and simple method of detoxifying AZC from water samples. Thus, TiO2+5 mmol/L NO3+pH 9.0 is anticipated to be a promising semiconductor-based photocatalysis for the remediation of antibiotic-contaminated wastewater.