Degradation of acidic aqueous solutions of the diazo dye Congo Red by photo-assisted electrochemical processes based on Fenton’s reaction chemistry

Comparative use of anodic oxidation, electro-Fenton and photoelectro-Fenton with Pt or boron-doped diamond anode to decolorize and mineralize Malachite Green oxalate dye

“…Oxalic, formic and oxamic acids are the final by-products that are directly mineralized to CO 2 [4]. All the detected acids form Fe(III) complexes to a large extent in the EF and PEF processes [33][34][35][36][37]. It is noticeable that the starting dye solution already contained 48 mg dm À3 of oxalic acid.…”

“…To do this, 0.50 mmol dm À3 Fe 2+ was added to the solution, since this catalyst concentration has been found optimal for the EF treatments of aromatic azo dyes using an air-diffusion cathode [33][34][35][36][37]. For comparison, these trials were also performed at 66.7 mA cm À2 for 360 min, and no significant variation of the solution pH was observed during the runs, as stated above for AO trials.…”

“…The PEF process has been extensively applied to the treatment of azo dyes [24,[34][35][36][37][38][39], the most common pollutants in dyeing effluents, but no information on its viability to destroy dyes with a triphenylmethane group has been previously reported. To clarify the oxidation power of this method over dyes with this chromophore group, we have undertaken a study on the comparative degradation of Malachite Green by AO, EF and PEF.…”

“…Fe 2+ (4) In our laboratory, we are also developing the photoelectroFenton (PEF) process, where the solution treated by EF is simultaneously illuminated with UVA light [34][35][36][37], yielding: (i) the photoreduction of Fe(OH) 2+ , the pre-eminent species at pH 3, to regenerate Fe 2+ ion with larger OH production by reaction (5), and (ii) the photolysis of generated Fe(III)-carboxylate intermediates via reaction (6). Recently, Khataee et al [38,39] reported that the addition of oxalate ion catalyzes the PEF process due to the enhancement of Fe 2+ regeneration via reaction (6).…”

Hydrothermal electrocatalytic oxidation for the treatment of herbicides wastewater

“…Moreover, pollutants and their intermediates can also be adsorbed on the surface of the electrode, resulting in the passivation of the electrode, which will decrease the decomposition rate greatly, especially at a high pollution concentration (Brillas et al 2004). To obtain a fast degradation of pollutions, even at the high concentration, many other techniques combined with EO were developed, such as microwave, ultrasound, Fenton oxidation, and photoelectric-synergistic catalytic oxidation Souza et al 2015;Iglesias et al 2014;Solano et al 2015). In these reaction systems, the problems induced by mass transfer or electrode passivation can be well dissolved; thus, enhanced degradation efficiency can be achieved.…”