Catalytic effect of lucunary heteropolyanion containing molybdenum and tungsten atoms on decolorization of direct blue 71

In this research,a lucunary Keggin structure,[PMo2W9O39]7- was selected as an efficient homogenous catalyst for degradation of an azo dye（direct blue 71） and a simple method was developed for degradation of DB71.The method is based on the oxidation of azo dye in the presence of a lucunary Keggin form of polyoxometalates,K7[PMo2W9O39]? 19H2O,as a homogenous catalyst at room temperature.The reaction is monitored spectrophotometrically by measuring the absorbance of dye atλ=585 nm.Some parameters including concentration of catalyst,concentration of H2O2,pH and reaction time were investigated and optimized. Results show that K7[PMo2W9O39]? 19H2O is more efficient in the presence of hydrogen peroxide.Degradation of dye in the presence of the catalyst and H2O2 could lead to the disappearance approximately 65%of dye after 60 min.But degradation for the same experiment performed in the absence of catalyst or in the absence of H2O2 was 22%or 5%respectively.Approximately 87% azo dyes has been eliminated after 90 min in the presence of catalyst,H2O2 and optimize conditions(0.6 g/L of K7[PMo2- W9O39H9H2O,0.08 mol/L hydrogen peroxide and room temperature).