Photocatalytic Degradation Mechanism of Malachite Green under Visible Light Irradiation over Novel Biomimetic Photocatalyst HMS-FePcs

Upon visible light irradiation in the presence of H2O2, the novel catalyst HMS-FePcS was highly effective for the degradation of nonbiodegradable malachite green (MG). High-performance liquid chromatography spectra and mass spectrometry spectra during the degradation process were analyzed to show that the MG degradation included its decoloration followed by the mineralization of intermediates. More than ten intermediates were confirmed through GC-MS, and the most probable degradation pathway for MG was proposed. The C–C bond between the central carbon atom and N,N-dimethylaminobenzyl was broken first to give the intermediate 4-(N,N-dimethylamino) methylbenzylone. Subsequently, 4-(N,N-dimethylamino) methylbenzylone reacted with strongly oxidative hydroxyl radicals. Finally, benzene rings were opened, and many small molecules such as fatty acids were produced.