Congo red dye removal from aqueous solutions by photocatalytic redox reactions: Degradation kinetics and simulation using dispersion model

This study degrades Congo red dye in aqueous solutions using redox reactions and Anatase nano-TiO2 as a catalyst, examining the kinetics of photodegradation through redox reactions. Then, a model based on the dispersion number estimates the efficiency of different plug flow reactors (ideal and nonideal flow states up to a mixed flow reactor). The photocatalytic redox reactions were carried out in a closed batch photoreactor using 0.2 g/L Anatase nano-TiO2 as a catalyst to remove different initial concentrations (32, 71, and 178 ppm COD) of the dye from its neutral aqueous solutions at 40 oC. The air was supplied to the reactor as an oxygen source at 0.2 L/min. The COD removal values decreased with the increasing initial dye concentration, and the best removal value was recorded (89.47 %) for the lowest initial COD (32 ppm) after 255 minutes of radiation. The kinetics study showed that the dye removal followed a first-order reaction model. Effects of initial concentration, dispersion number, and space-time on the organic distribution through the reactors were studied and discussed using a developed mathematical model based on the dispersion approach for the nonideal flow in reactors. The simulated results show that the ideal plug flow reactor (zero dispersion) performance was better than that of the nonideal plug flow reactor, and the performance decreased with the increasing dispersion number and gave the worst performance in the mixed flow reactor (infinity dispersion).