Photocatalytic degradation of red dye: optimisation using RSM

The aim of this research was to apply experimental design methodology to the optimisation of the photocatalytic degradation of red dye present in waste water. This paper reports the broad range of several photocatalyst composite efficiencies for photocatalytic degradation of red dye in waste water samples from textile industries. Three composites, which were graphitic carbon nitride (g-carbon nitride (C₃N₄))/zinc oxide (ZnO), g-carbon nitride/titanium dioxide (TiO₂) and zinc oxide nanoparticles, were prepared using different precursors (zinc chloride, zinc nitrate etc.). The catalysts were characterised by Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The catalytic performance of different photocatalysts was tested using different variables such as dosage, stirring speed, composite structure and dye concentration. Two methods were used to optimise the operating conditions. The results indicate that the photocatalytic degradation of the red dye solution at the resulting optimum condition, which was found to be after 90 min of ultraviolet irradiation, can reach 68, 57 and 53% when using zinc oxide nanoparticles, titanium dioxide/carbon nitride and zinc oxide/carbon nitride, respectively, as catalysts.