A comparative study of quantum yield and electrical energy per order (EEo) for advanced oxidative decolourisation of reactive azo dyes by UV light

This paper evaluates the quantum yield and electrical energy per order (EEo) efficiency of Reactive Orange 4 (RO4) and Reactive Yellow 14 (RY14) azo dyes by three advanced oxidation processes (AOPs). Both dyes were completely decolourised by all these processes. The relative decolourisation efficiencies of these processes were in the following order: Fe2+/H2O2/UV > UV/TiO2 > UV/H2O2. The low efficiency of UV/H2O2 process is mainly due to low UV absorption by hydrogen peroxide at the 365 nm. The figure of merit EEo values showed that UV/H2O2 process consumes more electrical energy than the other two processes. The electrical energy consumption is in the following order: UV/H2O2 > UV/TiO2 > Fe2+/H2O2/UV. At low initial dye concentration higher quantum yield was observed in UV/TiO2 process, whereas in photo-Fenton process higher quantum yield was observed at high initial dye concentration. The structure of dye molecule also influences the quantum yield and EEo value.