Reusable hybrid nanocomposites for clean degradation of dye waste under visible light

Herein we report on the degradation performance of three phthalocyanine-photosensitized TiO2 nanocomposites on waste dyes such as Ponceau 4R, Sella Fast Black, Congo Red, Select Brown, Indigo Carmine, Brilliant Blue, Fuchsin, Fluorescein and Naphthol Yellow S. All experiments were carried on at neutral pH, in ambient conditions, requiring only visible light and no additional oxidants. Chlorinated copper (II) α-phthalocyanine
(αClCuPc), copper (II) β-phthalocyanine (βCuPc), and tetra-sulfonated copper (II) β-phthalocyanine (βSCuPc)
increased the decolourization efficiency of TiO2 from moderate to high degrees, i.e., 30–100%, even for recalcitrant azo-dyes such as Ponceau 4R, Sella Fast Black, Congo Red and Select Brown. Moreover, the photosensitized catalysts display good thermal, operational stability, and reusability, providing total organic carbon (TOC) removal above 50% within 180 min in batch conditions. The reactive oxygen species were generated in the presence of dissolved oxygen, through the activation of phthalocyanine/TiO2 and it can be combined further with enzymatic/microbial treatment to achieve total mineralization.