Photocatalytic degradation of azo-dye Acid Red 18

The presented studies have focused on application of photocatalysis in degradation of azo-dye Acid Red 18 (C20 H11 N2 Na3 O10 S3) under UV irradiation. The effect of parameters such as initial dye concentration and catalyst dosage on the photocatalytic degradation of model dye was investigated. Another important factor affecting the photodegradation process performance was the temperature of the reaction mixture. The reaction temperatures were equal to 293, 323, 333 and 343 K. The initial dye concentrations amounted to 10 and 30 mg/dm3 and the photocatalyst (TiO2 Aeroxide® P25, Degussa, Germany) dosage was in the range of 0.1–0.5 g/dm3. The effectiveness of model dye photodecomposition was evaluated on the basis of changes of Acid Red 18 and total organic carbon (TOC) concentration and total dissolved substances (TDS) content. The effectiveness of photodecomposition of Acid Red 18 increased with increasing the catalyst concentration. However, an unfavourable effect of light scattering and reduction of light penetration through the solution in case of photocatalyst loading of 0.5 g/dm3 was observed. It was found that a linear correlation between the apparent rate constant and the reaction temperature exists in the range of 293–333 K. At the temperature of 343 K a decrease in the reaction rate was observed.