Reactivity of Cu2O-Cu in the Discoloration of Methylene Blue via a Heterogeneous Fenton-Like Process

In this study, copper particles were synthesized by using sodium ascorbate as a green reducing agent under atmospheric conditions. The product was micron-sized and mainly formed by metallic copper Cu with a minor presence of Cu2O. The product was used as a catalyst in the discoloration of methylene blue in a heterogeneous Fenton-like process in which H2O2 was produced in situ. The effect of different parameters such as copper loading, dye concentration, pH of the solution, and temperature was studied. The total discoloration was achieved after 42 min with 30 mg of copper at 60 °C and pH= 3. The amount of H2O2 produced in situ during methylene blue discoloration was evidenced by the permanganate method. It was found the formation of 110 µM after 40 min. The external addition of H2O2 at 0.001 M reduced the time for total discoloration to 10 min and the application of 40 kHz ultrasounds reduced the time further to 6 min.