The study on a mixed-phase I–N-TiO2 for the treatment of azithromycin wastewater under visible light

Abstract

Photocatalysis has attracted worldwide research interest for several decades because of its potential utilization of solar energy. It has been demonstrated that TiO2 is one of the most significant inorganic photocatalytic materials [1, 2]. However, due to the large band gap of *3.2 eV, TiO2 can only be activated in UV region [3]. To enhance its lightabsorbing properties and photocatalytic efficiency under visible light, many attempts have been carried out, such as selective ion doping [4–12], noble metal supporting [13, 14], and composite-type semiconductor preparation [15–18], etc. Among these attempts, TiO2 materials modified with two types of non-metal ions have attracted great attention over recent years, owing to their enhanced photocatalytic activity, for instance, F–I, C–N, N–F, N–P, and B–N-codoped TiO2 [19–24]. In addition, studies show that TiO2 with mixed phases could enhance photocatalytic activity because of the more efficient electron–hole separation on the ‘‘hot spots’’ at the rutile-anatase interfaces [25, 26]. In contrast to the above-doped materials, the doping I and N in TiO2 lattice for substituting the similarradius Ti and O, respectively, has been much less explored [27]. Up to now, only one literature about N–I-TiO2 has been found, which is synthesized by hydrolysis method, and N–I-TiO2 exists only in anatase phase [27]. In this work, using precipitation-grinding method and controlling the calcined temperature at 350 C, we firstly synthesized a mixed-phase I–N-TiO2 material. It could be expected that I–N-codoped TiO2 with mixed phases may have a significant effect on further improving the photocatalytic activity of TiO2 and inducing a remarkable visible-light activity. Azithromycin, which played a major role in the clinical therapy of the infection when the SARS crisis broke, is a kind of macrolide antibiotics commonly used in clinic. While the Azithromycin pharmaceutical wastewater is considered as an important class of organic pollutants, because of its potential hazardous effects on human being and the aquatic ecosystem [28, 29]. Therefore, it is imperative to develop effective methods for treatment of APW. Recently, the application of TiO2 in environmental purification appears to be very attractive, due to the environmentally friendly purification process. In this study, the mixed-phase I–N-TiO2 was applied to treat APW. The result shows that the mixed-phase I–N-TiO2 exhibits superior photocatalysis activity of APW under visible light.