Photoassisted hetero-Fenton mineralisation of azo dyes by Fe(II)-Al2O3 catalyst

Photoassisted Fenton mineralisation of two azo dyes Direct Red 23 (DR 23) and Reactive Orange 4 (RO 4) was studied in detail using a Fe(II) loaded Al2O3 as a heterogeneous catalyst in presence of H2O2 and UV-A light. 25 and 15% FeSO4 loaded Al2O3 show the maximum efficiency in the degradation of DR 23 and RO 4 respectively. The effects of catalyst loading, H2O2 concentration, initial solution pH and initial dye concentration on photodegradation were investigated and the optimum conditions are reported. DR 23 undergoes easy degradation when compared to RO 4. The difference is due to the presence of stable triazine ring system in RO 4. The catalyst is reusable and the leaching of Fe(II) from the catalyst in each run is less than 10% in the pH range 2–7.