The vanadium-substituted heteropolytungstate catalyzed oxidation of the organic dye by H2O2 in an aqueous solution

Abstract

The main objective of this work is to study the oxidation of the acid orange 7 (AO7) in an aqueous solution by using the hydrogen peroxide in the presence of vanadium substituted heteropolytungstate (α 1 P 2 W 17 VO 62 ) 6− as a catalyst. The effects of various experimental parameters on the oxidation reaction of the dye were investigated. And they are as follow: The H 2 O 2 concentration, the mass of the catalyst, and the dye concentration. The optimum conditions were determined. In addition, it was found that the efficiency of the degradation is obtained after 80 min of reaction, and it was about 100%. The optimal parameters were: initial pH = 4; [H 2 O 2 ] 0 = 1 mM; catalyst mass = 0.05 g; for a concentration of the dye [AO7] 0 = 2 mg/L. The kinetic oxidation of the AO7 by this catalytic system was also elucidated and based on experimental data. The oxidation of the AO7 follows a pseudo second-order Kinetic model. The activation energy, as well as the activation enthalpy and the entropy were calculated by using respectively the Arrhenius and the Eyring equations. The oxidation of the AO7 by the H 2 O 2 and the (α 1 P 2 W 17 VO 62 ) 6− requires a small amount of energy and has an endothermic nature. KeywordsThe Vanaduim-substituted heteropolyanions · A homogeneous catalysis · The azo dyes · The hydrogen peroxide · A kinetic and thermodynamic study · The water treatment * Ouahiba Bechiri, bechirio@yahoo.fr |