Design of a new ZnO photocatalytic Fenton-like system for enhancing the removal of methylene blue at neutral pH

Abstract

Although doping, nanostructuration, metallization, and binary/ternary oxide systems are widely used to improve the degradation kinetics in photocatalytic processes, rapid electron _ hole recombination remains one of its major limitations. On the other hand, homogeneous photo-Fenton-like processes suffer from the slow regeneration of Fe3+/Fe2+ catalysts and the formation of iron sludge at pH > 3. In this work, a new catalytic system is designed based on the coupling of nanostructured ZnO thin films photocatalysts with Fe3+/H2O2 (Fenton-Like) for the degradation of methylene blue (MB) molecules under UVA irradiation, at near-neutral pH (7.5). This coupled process promotes the formation of additional reactive oxygen species and reduces the formation of sludge by accelerating the regeneration of the iron catalysts in the medium. Furthermore, it exhibits a single kinetic regime of degradation with a rate constant of 0.0049 min−1 exceeding the sum of both individual processes and allowing therefore the removal of 94 % of MB after 480 min.