Degradation and mineralization of Calcon using UV 365/H 2O 2 technique: Influence of pH

Abstract

Degradation and mineralization of Calcon, an azo dye in aqueous solution were studied, probably for the first time using UV 365/H 2O 2 technique at various pHs. Higher degradation of Calcon is achieved in strong basic medium (99.4% at pH = 12.6 at 1260 μW cm – 2 ) than in strong acid medium (≈96% at pH 1.0 and 3.0 at 1260 μW cm – 2 ) both in the presence and absence of H 2O 2. Higher degradation under strong alkaline medium may partly be attributed to the neutralization of the acids formed in the mineralization process and partly to the involvement of additional HO radicals. The high degradation in the absence of H 2O 2 under strong acidic medium may be attributed to the role played by the counter ion of the acid used for adjusting the pH; SO 4 2− in the present case. The degree of mineralization is more in the presence of H 2O 2 than in its absence and is pH dependent (pH 1 > pH 12.6 > pH 3). The results show that strong acidic and basic media favor degradation and that mineralization of dye molecules in neutral form is more favored than in anionic form.