Heterogeneous photocatalytic degradation of the anthraquinonic dye, Acid Blue 25 (AB25): a kinetic approach

The photocatalytic degradation of the anthraquinonic dye, Acid Blue 25 was investigated in aqueous solutions containing TiO2 suspension as photocatalyst. The influence of parameters such as adsorption of the dye onto TiO2, pH, temperature, catalyst concentration and photon flux were studied. Results showed that adsorption played an important role in the control of the photocatalytic degradation rate and an optimal TiO2 concentration of 2.6 g L−1 was determined. By comparing the disappearance of AB25 followed by HPLC–DAD (high performance liquid chromatography–diode array detector) and the bleaching of the solution followed by UV-Vis spectrometry (wavelength of analysis=600 nm), two different kinetics were found proving that some of the intermediate products were still colored. This was confirmed using HPLC–DAD and HPLC–MS (high performance liquid chromatography—mass spectrometry) analysis.