Photocatalytic Destruction of Pharmaceutically Active Compounds by Hydrogen Peroxide Immobilized on TiO2

Abstract

The widespread application of pharmaceutically active compounds all over the world and the imperfection of traditional water treatment technologies lead to the appearance of these preparations and their metabolites in purified waste and surface waters. Contemporary advanced oxidation processes (AOPs) based on the generation of powerful OH radicals from environmentally friendly oxidants (O₂, O₃, H₂О₂) under UV radiation and the application of titania as a photocatalyst are able to provide the complete destruction of many ecotoxicants to CО₂, H₂О, and inorganic ions, i.e., their mineralization. A promising trend in expanding the capabilities of heterogeneous AOPs is the use of titania, which is deposited (immobilized) on solid supports to avoid the terminal nanosized powder separation stage. The kinetics of photocatalytic and heterogeneous photocatalytic destruction with hydrogen peroxide has been studied for popular cheap drugs, such as aspirin, salicylic acid, and analgin, in an aqueous medium in a reactor with TiО₂ immobilized on a large-pore ceramic support under UV-C irradiation. It has been shown that the Н₂О₂/TіО₂/UV photocatalytic system is able to provide the almost complete (96–100%) primary destruction of salicylic acid and aspirin (C₀ = 0.2 mM) and analgin (C₀ = 0.1 mM) at a maximum degree of mineralization of 85, 84, and 71%, respectively, for 3 h at an oxidant utilization rate ≥90%. The direct photolysis of all three preparations for 3 h has led their molecules only to slight initial transformation (≤41% according to spectrophotometric data) accompanied by a low degree of mineralization (≤6%).