Photocatalytic degradation of an azo dye using immobilised TiO2 nanoparticles on polyester support: central composite design approach

In this Letter, optimisation of the degradation of Reactive Orange 16 (RO16) by UV/TiO₂ process in recirculated tubular photoreactors was investigated by central composite design (CCD). Immobilised TiO₂ nanoparticles (100% anatase and average particle size of 6.7%nm) on the polyester support were used for the photocatalytic degradation. The applied TiO₂ nanoparticles were characterised by X-ray diffraction and transmission electron microscopy. The morphology of immobilised TiO₂ nanoparticles on the polyester support was observed by scanning electron microscopy. Using the CCD method, a model was developed for prediction of decolourisation efficiency as a function of independent operational parameters, including initial concentration of RO16 (5-25-mg/L), flow rate (5-15-L/h), temperature (14-46-C) and reaction time (30-150-min). The obtained results from the model are in good agreement with the experimental data (R²=0.9671 and Adj-R²=0.9383), and the optimum conditions for maximum degradation of RO16 can be calculated by the model. Moreover, this model is applicable to find individual and interactive effects of mentioned parameters. The mineralisation of RO16 was monitored by the chemical oxygen demand during the process.