Sunlight Induced Decoloration/Degradation of Non-Biodegradable Orange II Dye by Advanced Oxidation Technologies in Homogeneous and Heterogeneous Media

Abstract

Light and dark oxidation processes of organic compounds involving H

Bleaching and photobleaching of Orange II within seconds by the oxone/Co2+ reagent in Fenton-like processes

“…) and inserting this expression in (11): (5)- (9) is the production of sulfate radicals in reaction (6). Since reaction (9) is kinetically faster than reaction (8), the bleaching of Orange II (Fig.…”

“…4a shows that no photobleaching takes place when Co 2+ -ions are absent suggesting that the chain radical branched reaction only occurs when the oxone decomposition is mediated by Co 2+ -ions. When the oxone and Co 2+ are added in solutions containing organic compound(s), the formation of peroxides (ROOH) in radical chain processes have been reported [6,8,9]:…”

“…Only short treatment times when using expensive photons and oxidant(s) in a suitable reactor will allow AOT's treatments to compete with the more traditional non-destructive technology. Several techniques such as Fenton [6], photo-Fenton [7] and TiO 2 photocatalysis [8] have been used to abate the model azo-dye, Orange II.…”

“…The mineralization of pollutants has been carried out in recent years using peroxodisulfates as oxidants in the presence of TiO 2 in the AOT's field [6,[8][9][10]. Malato et al [11] have successfully tested peroxodisulfate (S 2 O 8 2− ) and oxone (2KHSO 5 ·KHSO 4 ·K 2 SO 4 ) which is essentially HSO 5 − and also known as peroxomonosulfate (PMS).…”

“…AOT's [10][11][12] uses UV-Vis light to activate the degradation of many organic compounds through the formation of metallo-complexes like: ligand to metal (LMCT), metal to ligand or ligand to ligand (LLCT) charge transfer photo-dissociation states leading to a variety of radicals under light irradiation [6][7][8][9][10]21,23,24]. Ozone has also been used as a source of oxidative radicals in waste water treatment [2].…”