Exploring a substitute for hydrogen peroxide in Fenton process – A case study on the COD removal of Acid Orange 8

Abstract

Hydrogen peroxide (HP) is widely used in advanced oxidation processes (AOPs). This study evaluates the chemical oxygen demand (COD) removal efficiency of Acid Orange 8 (AO 8) at a higher concentration by modified Fenton processes using substituted HP such as tert-butyl hydroperoxide (TBHP) and sodium perborate (SPB) and sodium persulphate (SPS) as oxidants. Under optimal conditions, COD removal was found to be 72.8 and 58.9% at pH 3.0 and 6.5 in the Fenton process in 300 min. The COD removal efficiency of different systems is in the order: Fe²⁺/SPB>Fe²⁺/HP>Fe²⁺/TBHP>Fe²⁺/SPS indicating the possibility of using SPB as a substitute for HP and SPS. The order of efficiency is attributed, among other factors, to their ability to produce HO^. radicals. Various anions are shown to exhibit an inhibitory effect in the order:  I^->Br^->F^->Cl^->SO₄^2->NO₃^-. The inhibitory effect of Cl^- is observed at higher concentrations than F^- and Br^-, even though I^- displays inhibition at all concentrations. Finally, COD removal kinetics and the degradation mechanism, based on the identified intermediate products, were determined in this study.