Green ternary composite of graphitic carbon nitride/TiO2/ polyorthoanisidine for the enhanced photocatalytic treatment of Direct Red 28 for industrial water treatment solutions

Industrial dye effluent causes significant risks to the environment. The present study was focused on photocatalytic degradation of the dye Direct Red 28 using a ternary composite of graphitic carbon nitride, TiO₂, and polyorthoanisidine (g-C₃N₄/TiO₂/POA), prepared by <i>in-situ</i> oxidative polymerization <i>o-</i>anisidine. The synthesized composite g-C₃N₄/TiO₂/POA properties were characterized using different analytical techniques. X-ray diffraction (XRD) results revealed the prominent pattern of TiO₂ and g-C₃N₄ in the composite peak at 2θ° while Fourier transform infrared (FTIR) results provided the confirmation peaks for g-C₃N₄/TiO₂/POA and POA at 1,110 cm^-1 and 1,084 cm^-1 for C-O-C ether. Scanning electron microscopy (SEM) demonstrated an increase in the average size of the composite up to 428 nm. The energy-dispersive X-ray spectroscopy (EDX) spectrum provided the weight percentages of the C, O, and Ti in the composite were 8.5%, 45.69%, and 45.81%, respectively. The photocatalytic degradation of Direct Red 28 dye under UV irradiation using a composite showed that 86% Direct Red 28 dye was degraded by a 30 mg/L dose of g-C₃N₄/TiO₂/POA in 240 min at pH 2. After four consecutive cycles, the utilized composite showed 79% degradation of Direct Red 28, demonstrating the stability and effectiveness of the g-C₃N₄/TiO₂/POA photocatalyst. The high reusability and efficiency of the g-C₃N₄/TiO₂/POA composite are due to increased light absorption range and reduced e^-/h⁺ recombination rate in the presence of g-C₃N₄ and POA.