The oxidation study of methyl orange dye by hydrogen peroxide using Dawson-type heteropolyanions as catalysts

In this research, the oxidation of an azo dye (methyl-orange) by H2O2, in an aqueous solution, using a Dawson-type heteropolyanion (α2P2W12Mo5O61Fe)7− as catalyst was studied. The effects of different parameters dye oxidation were investigated. The studied parameters were: the initial pH, the initial H2O2 concentration, the catalyst mass and the initial dye concentration. The optimal conditions for a maximum discoloration efficiency (100 %) are: pH: 6, [MO]0 = 2 mg/L, Catalyst (α2P2W12Mo5O61Fe)7− mass: 1 g, [H2O2]0 =: 0.072 M. The effect of other Dawson-mixed heteropolyanions, such as (αP2W18O62)6−, (αP2W12Mo6O62)6− and (α2P2W12Mo5O61X)n− (X = Ni2+,Cr3+,Cu2+) on the dye oxidation at room temperature was evaluated. The stability of the catalyst after reaction was verified.