“…In this concentration range, 98% decolorization is achieved after less than 10 min. For higher H 2 O 2 concentrations, MG degradation rate decreases leading to 99%, 98%, and 88% decolorization for 5, 10 and 50 mM, respectively, after 1 h. An optimal H 2 O 2 concentration has already been reported in the Fenton oxidation of dyes [ 42 , 43 ]. Indeed, for high concentrations, H 2 O 2 excess acts as a scavenger of hydroxyl radical ( • OH), resulting in less dye degradation.…”