The main objective of this work was to study the degradation of Acid Orange 7 (AO7) dye in aqueous solution by hydrogen peroxide using HFe 2.

system in the decolorization of one common industrial azo dye, naphthol blue black (NBB). The effects of different parameter's dye decolorization were investigated. The studied parameters were: the initial pH, the initial H 2 O 2 concentration, the catalyst mass, and the initial dye concentration. The optimal conditions for a maximum discoloration efficiency (100%) are: pH: 3, [NBB] 0 = 10 mg/L, Catalyst mass : 0.3 g, [H 2 O 2 ] 0 = : 2 m M. The spectrophotometric analysis indicated that the decolorization of the azo dye with Fe(III)P 2 W 12 Mo 5 /H 2 O 2 was due to the reduction of the azo bonds. This study verifies the viability of the use of Fe(III)P 2 W 12 Mo 5 /H 2 O 2 in the decolorization of NBB.

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The synthesis, IR , 31 P NMR and cyclic voltammetry characterizations of a new Wells-Dawson-type heteropolyanions which contains iron HFe 2.5 P 2 W 18 O 62 , 23H 2 O and HFe 2.5 P 2 W 12 Mo 6 O 62 , 22 H 2 O are reported. The catalytic activity of these compounds was evaluated through the oxidation of methyl violet dye, by hydrogen peroxide. The influence of different parameters such as the initial pH, the initial H 2 O 2 concentration, the catalyst mass, and the initial dye concentration have been studied.

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