Photocatalytic degradation of polycyclic aromatic hydrocarbons under visible light irradiation in water using...

An extensive class of pollutants found in soil, water, and bottom sediments are categorized as polycyclic aromatic hydrocarbons. A possible method of breaking down polycyclic aromatic hydrocarbons is thought to be the photochemical approach. The potential application of mesoporous nanocomposites on TiO₂/MgO as catalysts for the photooxidation of polycyclic aromatic hydrocarbons under the influence of visible light was assessed in this work. TiO₂/MgO nanocomposites were successfully obtained by the self-propagating high-temperature synthesis using methotitanic acid and magnesium nitrate as metal precursors. An important step in the synthesis was the conversion of the titanium precursor into a water-soluble form with the subsequent addition of glycine and citric acid at a carbon/nitrogen (C/N) molar ratio of 0.25. This synthesis via solutions allowed the target materials with major phases of magnesium metatitanate MgTiO₃, magnesium dititanate MgTi₂O₅, and magnesium titanate Mg₂TiO₄ to be obtained after heat treatment at 750 °C. Heterostructured mesoporous TiO₂/MgO powders with a specific surface area of 22.0-28.4 m²/g had an average diameter of the predominant pores of 10-30 nm. The greatest degree of photocatalytic oxidation of fluorene, pyrene, and benzpyrene (80, 68, and 53%, respectively) was obtained when it was combined with the TiO₂/MgTi₂O₅/MgTiO₃ nanocomposite under visible light irradiation. This study showed that mesoporous TiO₂/MgO nanocomposites could be used as photooxidation catalysts for polycyclic aromatic hydrocarbons. The maximum level of photocatalytic oxidation of polycyclic aromatic hydrocarbons in TiO₂/MgO nanocomposites occurred at pH 7 and a photocatalyst dose of 1 mg/L under the influence of normal solar radiation.