Oxidative removal of Orange G by homogeneous advanced oxidation processes

Azo dyes represent approximately 60–70 % of all synthetic dyes produced worldwide and are rather difficult to degrade. In this study, we investigate the degradation of Orange G (OG) using two types of homogeneous advanced oxidation processes (AOP): a chemical degradation with bicarbonate activated hydrogen peroxide (BAP) and a photochemical process involving either hydrogen peroxide (H 2 O 2 ) or persulfate (S 2 O 8 2− ), irradiated with a low-pressure mercury lamp emitting at a wavelength of 254 nm (40 W). The degradation efficiency was compared against a UV-irradiated sample without any oxidants. The degradation follows an apparent first-order kinetics, with the rate constant values positively influenced by the increase in the concentration of oxidant species within the tested range. All tested methods proved to be clean and cost-effective, but the photodegradation systems (UV/S 2 O 8 2− and UV/H 2 O 2 ) are more efficient for removing this dye from wastewater. • UV/H 2 O 2 and UV/PS demonstrated superior efficiency compared to UV photolysis. • SO 4 ·- and · OH radicals were identified as the key oxidants in OG degradation. • The degradation rate followed pseudo-first order kinetics. • 85.5 % and 76.3 % TOC removal for UV/PS and UV/H 2 O 2 , respectively