Investigation of the degradation of acidic dye solutions containing azo groups by fenton process

In this study, the degradation of Acid Orange 8 (AO8), Acid Red 44 (AR44), Acid Red 66 (AR66) and Direct Blue 71 (DB71) azo dyes used widely in textile industry was investigated by Fenton process. On-line spectrophotometric method was used to follow the degradation of azo dyes. The effects of various operation parameters such as initial H2O2 concentration, initial Fe2+ concentration, pH of solution, initial dye concentration and temperature of solution on the degradation of AO8, AR44, AR66 and DB71 were investigated and the optimal operational conditions were determined. The experimental results showed that the optimal initial H2O2 concentration was 7,50x10-4 M for AO8 and AR66, 3,75x10-4 M for AR44 and 5,00x10-3 M for DB71. The optimal values of the initial Fe2+ concentration, pH and temperature of solution were found to be 2,5x10-5 M, 3,5 (in the range of 3,5 and 4,0 for AR44, AR66 and DB71) and 45 ºC, respectively. Under these optimal operation conditions, the decolorization percentages of AO8, AR44, AR66 and DB71 after 180 minutes were 99,43; 99,28; 99,59 and 99,75, respectively, in the presence of 2,94x10-5 M dye solution.