Degradation mechanism of diazo dyes by photo-Fenton-like process:Influence of various reaction parameters on the degradation kinetics

摘要

The degradation of diazo dyes Brilliant Yellow (BY) and Bismark Brown (BB) was investigated by the photo-Fenton-like process Fe~(2+)/ammonium persulphate (APS)/UV in acidic pH medium. The influence of various reaction parameters like pH, concentration of Fe~(2+) ions/APS, structure of the dye and effect of radical scavenger on the degradation kinetics is reported. The rate constant (k), catalytic efficiency (k_c) and process efficiency (Ф) are evaluated at different concentrations of Fe~(2+) ions. It was found out that the BB degrades at a faster rate than BY. The degradation process was followed by GC-MS technique. The results show that the initial step in the degradation of BB involves direct oxidation of azo chromophore, while in the case of BY the initial step is oxidation of azo group followed by the oxidation of ethylenic chromophore. Based on the obtained intermediates, probable degradation mechanism has been proposed. The results show that photo-Fenton-like process could be a useful and efficient technology for the mineralization of diazo dyes at lower concentrations of iron in acidic medium.