Abstract: Upon visible light irradiation in the presence of H2O2, the novel catalyst HMS-FePcS was found to be 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 decolorization 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.

Key words: visible light, malachite green, degradation mechanism, photocatalysis, iron sulfophthalocyanine