Fe-Modified TiO2 Nanotube Layer as a Photochemically Versatile Material for the Degradation of Organic Pollutants in Water

Abstract

TiO2 nanotube layers (TNT) are prepared by electrochemical anodization of Ti foil in an electrolyte composed of ethylene glycol, ammonium fluoride, and water. The surface of TNT is modified by iron using spin-coating of Fe(NO3)3/IPA (isopropyl alcohol) solution of different concentrations (10 μM−100 mM). The as-prepared materials are annealed at 450 ◦C for 2 h to form crystalline Fe-TNT. The phase identification and surface morphology of the materials are investigated by XRD and SEM/EDX, respectively. The novelty of this work is based on the investigation of different photochemical processes that could occur simultaneously, and it includes mainly photocatalysis and Fenton-based processes since iron is a Fenton-active element and TiO2 is a photocatalyst. To this end, the degradation of caffeine, an organic pollutant, is performed under solar-like radiation at pH = 3 using different systems that are: (i) Fe-TNT material alone; (ii) a radical precursor alone (H2O2 = 1 mM); and (iii) Fe-TNT combined with H2O2. It is worth noting the degradation mechanism of the organic pollutants occurs via advanced oxidation processes where hydroxyl radicals have been identified as the main reactive oxygen species. One of the main goals of this work is to determine the contribution of the different involved photochemical processes (photocatalysis, photo-Fenton, and photolysis) along with the potential synergy between all these processes. To resume, this work provides new insights into the concept of photochemical versatility (using Fe-TNT), which is scarcely described in the literature.