Electrochemical mineralization of the azo dye Acid Red 29 (Chromotrope 2R) by photoelectro-Fenton process

Routes for the electrochemical degradation of the artificial food azo-colour Ponceau 4R by advanced oxidation processes

“…As can be seen, after a poorly efficient early stage related to the aforementioned induction period, maximum MCE values of 55%, 29%, 21% and 18% were obtained after 90-120 min as current increased, whereupon the efficiency decayed due to the accumulation of by-products that were highly resistant to oxidation by BDD( • OH) and • OH and/or UVA photolysis. High current values are then preferred if time is the key parameter for applying the treatment, whereas such choice is detrimental in terms of energy consumption since parasitic reactions of BDD( • OH) and • OH are enhanced under such conditions, especially as the organic matter content diminishes [37][38][39][40][41][42].…”

“…Encouraging results have been obtained for the treatment of textile azo dyes by EAOPs with a BDD anode [36][37][38][39][40], and very recently we have even discussed the behaviour of two food azo dyes in such systems [41,42]. In the present work, aiming to gain more thorough knowledge about the fate of food azo-colours upon application of EAOPs, Ponceau 4R has been chosen as a model pollutant.…”

Photoelectrocatalytic/photoelectro-Fenton coupling system using a nanostructured photoanode for the oxidation of a textile dye: Kinetics study and oxidation pathway

“…In addition, the absorbance of the OG solution did not significantly vary during exposure to the UV lamp over 60 min, indicating that the dye was not directly photolyzed to any appreciable extent. The more efficient color removal obtained by the PEC/PEF process could be attributed to the faster oxidation of the OG dye and by-products (with similar absorbance of the target dye) that were formed during the degradation process (Almeida et al, 2012) due to the additional production of Å OH radicals by: (i) the photochemical reduction of Fe(OH) 2+ complexes from reaction (4) (Almeida et al, 2012), (ii) the photolytic cleavage of H 2 O 2 according to reaction (6) (Harir et al, 2008;Saquib et al, 2008) and (iii) the photo-generated holes (h + ) in the valence band of the Pt/TiO 2 NT photoanode (Almeida and Zanoni, 2014). Fig.…”

“…In these processes, H 2 O 2 is continuously http://dx.doi.org/10.1016/j.chemosphere.2015.04.042 0045-6535/Ó 2015 Published by Elsevier Ltd. electrogenerated to contaminated solutions as a product of the two-electron reduction of O 2 gas at carbonaceous cathodes, such as carbon-PTFE (Almeida et al, 2012;Moreira et al, 2014), carbon cloth (Peralta-Hernández et al, 2008), reticulated vitreous carbon (Xie and Li, 2006), activated carbon-fiber (Wang et al, 2008), graphite-felt (Zhou et al, 2012) or BDD electrodes (Cruz-González et al, 2012), according to the following reaction (1):…”

“…Electrochemical advanced oxidation processes (EAOPs) have widely been employed for the decontamination of wastewaters containing organic pollutants due to their versatility, high efficiency and environmental compatibility (Almeida et al, 2012). Their effectiveness is ascribed to the generation of hydroxyl radicals ( Å OH) with a high redox potential (E s ( Å OH/H 2 O) = 2.80 V/ SHE) that react non-selectively with the organic compounds until they are oxidized to CO 2 , water and inorganic ions Almeida et al, 2011).…”