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

Abstract

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.