Acid–Base Properties and Adsorption Activity of Iron-Containing Composites in the Photocatalytic Degradation of Organic Pollutants

The autowave combustion of ferroalloys (ferrovanadium, aluminum ferrochrome, ferroaluminum silicocirconium) in nitrogen are used to determine the phase composition of iron-containing metal–ceramic composites based on nitrides of aluminum, chromium, and vanadium. The content of iron on the surfaces of the composites is measured via scanning electron microscopy using an X-ray micro analyzer. The Hammett and Tanabe indicator reveals that aprotic Lewis basic centers (pK_a −0.29) and strong acidic Brønsted centers (pK_a 2.01, 4.1) dominate on the surfaces of chromium nitride-based composites. The surfaces of the samples based on vanadium nitride have many acidic Brønsted centers (pK_a 1.3–5.5). The correlation between the adsorption activity of composites and the studied organic pollutants (metamizole, cinnarizine, methylene blue, and methyl orange), plus the type and number of acid-base active centers on the surfaces of the materials, testifies to the dominance of chemisorption, for which mechanisms are proposed. The strong oxidative destruction of organic pollutants (64–96%) upon UV irradiation is due to the adsorption properties of the composites and the combination of heterogeneous photocatalysis and the homogeneous Fenton process.