UV light and Fe catalysed COD removal of AO 8 using NaOCl as oxidant.

The present study aims to establish NaOCl as a potential oxidant in the COD removal of Acid Orange 8 using UVC light (λ = 254 nm) and Fe as catalysts. The different systems used in this study are NaOCl, Fe/NaOCl, UV/NaOCl, and Fe/NaOCl/UV. All these process were found to be operative in acidic, neutral and basic medium. The initial decolorisation and COD removal efficiency (COD) for different systems follow the order: Fe/NaOCl/UV > UV/NaOCl > Fe/NaOCl > NaOCl. Nevertheless, NaOCl can alone be used in the treatment process considering its COD to the extent of 95% in 90 min. The change in pH of the solutions after treatment is an important observation - for non-UV systems it remained around 11.0 and 7.0 in other systems. Thus, UV systems are environmental benign. The effect of various anions on COD was tested in Fe systems. Presence of F ions were found to accelerate COD in both the systems. However, the effect is more pronounced in Fe/ NaOCl/UV, where complete COD was observed in the presence of 9.0 gl of F. The COD removal kinetics for all systems was studied using zero-order, first-order, second-order, and BMG kinetic models. BMG model was found to be more suitable among all and is in good agreement with COD of all systems. It is, therefore, established that NaOCl can serve as a powerful oxidant in the advanced oxidation process.