Fenton Reagent-Based Advanced Oxidation for the Degradation of Reactive Black 5 and Methylene Blue Dyes

This study investigates how Fenton oxidation affects the decolourization and mineralization of two dyes—an azo dye (Reactive Black 5) and a basic dye (Methylene Blue)—in water. A series of batch experiments were conducted to determine the optimal conditions for the process, including the starting concentrations of the dyes, dosages of hydrogen peroxide (H2O2) and ferrous sulfate (FeSO4), pH levels, reaction time, and temperature. The degradation of both dyes was assessed by measuring the extent of color removal and mineralization, using UV-visible spectrophotometry and chemical oxygen demand (COD), respectively. The most effective conditions were found to be at a pH of 3 and a temperature of 40°C, with 200 mg/L of Reactive Black 5 and 150 mg/L of Methylene Blue. For Reactive Black 5, the use of 30 mg/L FeSO4 and 300 mg/L H2O2 achieved 99.32% color removal, while 50 mg/L FeSO4 and 500 mg/L H2O2 resulted in 99.28% color removal for Methylene Blue after 25 minutes of treatment. COD reduction was 60% for Reactive Black 5 and 73.33% for Methylene Blue. These results indicate that the Fenton process can achieve nearly complete decolourization and significant, though partial, mineralization. Further analysis using GC-MS confirmed the breakdown of the dyes and showed the absence of certain toxic by-products after the treatment.