Visible Light-Induced Oxidative Degradation of Chloramphenicol by Iron-Containing Ceramic-Metal Composites

Autowave combustion of ferrosilicon aluminum with various metallic tantalum additives (5, 10, and 15 wt %) in nitrogen produces iron-containing ceramic-metal composites based on silicon nitride modified by the TaON semiconductor compound. The phase composition was determined by X-ray diffraction, and the surface morphology of the composites was studied by scanning electron microscopy (SEM). The surface iron composition was assessed using an attachment to a scanning electron microscope for X-ray microanalysis. The acid–base properties of the surface of the composites were studied by pH-metry and the Hammett–Tanabe indicator method with spectrophotometric indication. A comprehensive assessment of the acidity of the surface of the composites was performed, and the surface centers of the composites were identified. A wide range of acid–base sites (Lewis base centers, pKa –0.29), acid sites (pKa 1.3–6.5), and basic Brønsted sites (pKa 7–13) were found, indicating the adsorption activity of the composites to various pollutants. We studied the adsorption of chloramphenicol (CHL) on these composites and proposed the adsorption mechanisms. A correlation was found between the adsorption activity of the composites to СHL (pKa1 = 5.5; pKa2 = 11.3) and their acidic properties. The photocatalytic activity of the composites during the oxidative degradation of CHL is studied. Iron-containing ceramic-metal composites based on TaON-modified silicon nitride are promising photocatalysts for the oxidative degradation of CHL (85–91%) under visible light irradiation with the addition of H2O2. Such a high activity is due to their adsorption properties and the combination of heterogeneous photocatalysis and a homogeneous photo-Fenton system.