Optimization of photocatalytic activity of immobilized TiO2-P25 nanoparticles in the removal of phenazopyridine using response surface methodology

The photocatalytic degradation of phenazopyridine (PhP) as a model contaminant from pharmaceutical compounds was studied using batch-recirculated photoreactor packed with immobilized TiO2-P25 nanoparticles on glass beads. The effects of operational parameters (irradiation time, initial concentration of PhP, volume of solution, and volumetric flow rate) were evaluated by the response surface methodology (RSM). The proposed model of the RSM is a second order mathematical model. According to the results of ANOVA, initial concentration of PhP, volumetric flow rate, irradiation time, volume of solution, mutual effects of initial concentration of PhP x irradiation time, irradiation time x volume of solution and quadratic effects of initial concentration of PhP, and volume of solution are significant model parameters. The optimization process by RSM offers the following optimal conditions: PhP concentration 24 mg L-1, liquid volumetric flow rate 230 mL min(-1), irradiation time 30 min, and volume of solution 300 mL. Under these conditions, the proposed removal percent of RSM is 90.28% which have good correspondence with experimental removal percent (87.36%).