Photocatalytic Degradation of Chloramphenicol Using Iron-Containing Metal-Ceramic Composites Under Visible-Light Conditions

In the present study iron-containing, metal-ceramic composites based on silicon nitride modified with the semiconductor compound TaON were synthesized by autowave combustion in a nitrogen atmosphere of ferrosilicoaluminum with various additives (5, 10, 15 wt%) of tantalum metal. The phase composition was determined by the X-ray diffraction method, and the morphology of the surfaces of the composites was studied by scanning electron microscopy (SEM). Quantification of surface iron using a scanning electron microscope accessory for X-ray spectral microanalysis was performed. The acid-base properties of the surface of the composites were investigated by pH-metry and the Hammett and Tanabe indicator method with spectrophotometric indication. Integral evaluation of the surface acidity was performed, and the surface centres were identified. A wide set of acid-base centres was established. Lewis basic (pKa -0.29) and acid centres (pKa 1.3-6.5), and Bransted basic centres (pKa 7-13) were obtained. These results show the adsorption activity of the composites to various pollutants. The adsorption of chloramphenicol (CHL) was studied, and the mechanisms of adsorption processes were proposed. The adsorption activity of composites to CHL (pKa1=5.5; pKa2=11.3) correlates with their acidic properties. The photocatalytic activity of composites in the oxidative degradation of CHL was investigated. Iron-containing, metal-ceramic composites based on silicon nitride modified by TaON are promising photocatalysts for the oxidative degradation of CHL (85-91%) under visible light irradiation in the presence of H2O2. The high activity of the composites is caused by their adsorption properties and the combination of heterogeneous and homogeneous photo-Fenton photocatalysis systems. Contribution of the authors: the authors contributed equally to this article. The authors declare no conflicts of interests.

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