Effect of calcium oxalate on the photocatalytic degradation of Orange II on ZnO surface

The photocatalytic degradation of aqueous solution of Orange II, has been investigated in the presence of ZnO catalyst with calcium oxalate as sacrificial agent. This study demonstrated that the performance of ZnO photocatalyst can be improved by addition of calcium oxalate. Results show that adsorption is an important parameter controlling the degradation phenomena. Indeed, the added oxalate causes a drop in the pH medium, what causes a better adsorption of Orange II on the ZnO surface. The effect of calcium oxalate is to increase the concentration of superoxides (O 2 · ) and hydroperoxides (HO2·) radicals, which are key intermediaries in the mechanism of photodegradation because of their powerful force of oxidation.