UV-Activated and Fe2+-Catalyzed H2O2 for the Treatment of Dye-Contaminated Water: Kinetics, Mechanism and Toxicity Investigations

This study investigated the removal of methylene blue (MB) by different UV, UV-catalyzed H2O2 (UV/H2O2) and UV-and-iron-catalyzed H2O2 (UV/H2O2/Fe2+)-based advanced oxidation processes. At pH 6.0, the removal of MB (15 mg/L) was found to be 6.31% at 60 min for UV only. However, the combination of H2O2 (5 mM) with UV greatly enhanced the removal efficiency as 96.44% degradation of MB was found in the UV/H2O2 process at 60 min. Furthermore, the UV/H2O2/Fe2+ process was observed to be even more efficient than UV/H2O2, achieving 99.11% MB degradation at 30 min of treatment under the experimental conditions of [MB]0 = 15 mg/L, [H2O2]0 = 2 mM, [Fe2+]0 = 0.5 mg/L, and pH0 = 3.0. Furthermore, the removal of TOC was found to be 59 and 71% for UV/H2O2 and UV/H2O2/Fe2+, respectively. The pH did not change the efficiency of the UV/H2O2 process significantly; however, it greatly affected the efficiency of the UV/H2O2/Fe2+ system. The results demonstrate that both UV/H2O2 and UV/H2O2/Fe2+ could be used for the effective degradation and mineralization of MB.