Electrochemical degradation of the Disperse Orange 29 dye on a β-PbO2 anode assessed by the response surface methodology

Electrochemical degradation of the herbicide picloram using a filter-press flow reactor with a boron-doped diamond or β-PbO 2 anode

“…6a, active chlorine has a significant effect on the rate of initial electrodegradation of PCL; furthermore, this effect is much more marked when the solution pH is kept at 6 or is not controlled. [53] or Aquino et al [44]), its higher concentration at pH 6 seems to be the reason why the initial electrodegradation of PCL occurs at a higher rate at this pH value (see Fig. 6a).…”

“…The BDD and β-PbO2 anodes have been extensively investigated in the electrooxidation of solutions/effluents containing organics due to their excellent chemical stability and high overpotential for the oxygen evolution reaction, which favors • OH electrogeneration [23][24][25]29,31]. Despite the fact that • OH is a potent oxidant, other types of oxidants may be electrolytically generated if certain chemical species are present in solution, such as Cl -or SO41 -ions, when their oxidation leads to the formation of active chlorine (Cl2, HOCl, or OCl -, whose individual concentrations are dependent on the concentration of Cl -and the solution pH, temperature, and ionic strength [44]) or persulfate ions (S2O8 2-) [26,45]; furthermore, hydrogen peroxide (H2O2) may be formed by the combination of hydroxyl radicals [43]. These oxidants, once formed, diffuse to the bulk of the solution; thus, they may decrease the organics oxidation dependence on mass transfer to the electrode surface and, hence, increase the process rate and efficiency.…”

“…Picloram electrodegradation when Cl -ions are present in the supporting electrolyteThe presence of Cl -ions in the supporting electrolyte commonly leads to the electrogeneration of active chlorine, which, as mentioned in the Introduction, might contribute to increase the rate and efficiency of the organics electrooxidation. As discussed and exemplified by Aquino et al[44], active chlorine involves the Cl2, HOCl, and OCl -species, whose individual concentrations are dependent on the concentration of Cl -and the solution pH, temperature, and ionic strength. Considering that those species have different oxidation powers [E 0 (Cl2) = 1.36 V, E 0 (HOCl) = 1.49 V, and16 E 0 (OCl -) = 0.89 V vs. SHE], the predominance of one or another might influence the obtained results; thus, this possible effect has been investigated in some cases.…”

“…Considering that those species have different oxidation powers [E 0 (Cl2) = 1.36 V, E 0 (HOCl) = 1.49 V, and16 E 0 (OCl -) = 0.89 V vs. SHE], the predominance of one or another might influence the obtained results; thus, this possible effect has been investigated in some cases. For instance, Aquino et al[44] reported that the best conditions for COD abatement of a solution of the Direct Orange 29 dye containing Cl -ions in the supporting electrolyte (0.10 M Na2SO4) were neutral to alkaline solutions (for [NaCl] < 1.0 g L -1 and high temperatures), whereas those for TOC abatement were slightly acidic to alkaline solutions (for 1.2 g L -1 ≤ [NaCl] < 1.7 g L -1 ). On the other hand, Degaki et al[26] showed that the electrochemical decolorization of the Reactive Blue 19 dye is significantly enhanced by the presence in solution of electrogenerated active chlorine, especially at pH 1, when Cl2 is the predominant active-chlorine species.…”

Electrochemical degradation of the Acid Orange 10 dye on a Ti/PbO2 anode assessed by response surface methodology

“…It is also possible to determine the relationships and interactions among the variables through these techniques. In this regard, statistical methodologies, such as the response surface methodology (RSM), are suitable for studying and modeling a particular system; for example, RSM has been used for the investigation of electrochemical degradation of the Disperse Orange 29 dye [31].…”