| Summary: | <p class="PaperAbstract">Small volumes (100 mL) of acidic aqueous solutions with 30-200 mg L<sup>-1</sup> TOC of the toxic azo dye Acid Red 1 (AR1) have been comparatively treated by various electrochemical advanced oxidation processes (EAOPs). The electrolytic system consisted of a BDD anode able to produce <sup>·</sup>OH and an air-diffusion cathode that generated H<sub>2</sub>O<sub>2</sub>, which subsequently reacted with added Fe<sup>2+</sup> to yield additional <sup>·</sup>OH from Fenton’s reaction. Under optimized conditions (i.e., 1.0 mM Fe<sup>2+</sup>, 60 mA cm<sup>-2</sup>, pH 3.0, 35 ºC), the analysis of the initial rates for decolourization and AR1 decay assuming a pseudo-first-order kinetics revealed a much higher rate constant for photoelectro-Fenton (PEF, ~ 2.7x10<sup>-3</sup> s<sup>-1</sup>) compared to electro-Fenton (EF, ~ 0.6x10<sup>-3</sup> s<sup>-1</sup>). Mineralization after 180 min was also greater in the former treatment (90 % vs 63 %). The use of UV radiation in PEF contributed to Fe(III) photoreduction as well as to photodecarboxylation of refractory intermediates, yielding a mineralization current efficiency as high as 85% during the treatment of solutions of 200 mg L<sup>-1</sup> TOC. Primary reaction intermediates included three aromatic derivatives with the initial naphthalenic structure and four molecules only featuring benzenic rings, which were totally mineralized in PEF.</p><p class="PaperTitle"> </p>
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