Fe-Impregnated Charcoal for Enhanced Removal of Azo Dye Reactive Blue 194: Fenton-like Oxidation Conditions and Fate of Degradation Products in Activated Sludge System

This study aimed to assess the effectiveness of Fe-impregnated charcoal (FIC) in removing azo dye Reactive Blue 194 (RB) under various Fenton-like oxidation (FLO) conditions, as well as investigate the fate of degradation products when discharged into an activated sludge system. The optimal FIC concentration for achieving maximum decolorization activity was found to be 0.5 to 1 g/L, resulting in a removal efficiency of over 95% within 90 minutes. However, the decolorization efficiency decreased as the initial dye concentration increased, reaching 83.6% at 0.5 g/L within 90 minutes. Other optimal reaction conditions included 80 mg/L H2O2 at an initial pH of 3.5 and a temperature of 25°C. The impact of tap water and chemical additives commonly used in dyeing baths, such as acetic acid and sulfonic acid, on the FLO rate was investigated. The use of tap water resulted in a 3.4% reduction in decolorization activity, while the addition of 0.3 g/L sulfonic acid led to a decrease in color removal efficiency to 84.4% within 90 minutes, although the pH was maintained at the optimum condition. The treated solutions were transferred to a pre-adapted activated sludge system, and the resulting solutions after each stage were extracted and analyzed using GC-MS. The results revealed that the de-aromatization process began during the Fenton oxidation stage and was completed in the activated sludge system. However, certain phenolic compounds originating from the degradation of the parent dye remained unchanged throughout all stages