a b s t r a c tThe performance of three electrochemical advanced oxidation processes, namely electro-oxidation with electrogenerated H 2 O 2 (EO-H 2 O 2 ), electro-Fenton (EF) and photoelectro-Fenton (PEF) for the treatment of aqueous solutions of the food azo dye Ponceau 4R in an undivided cell with a BDD anode and an airdiffusion cathode was compared in terms of colour, dye concentration and total organic carbon (TOC) removals. PEF treatments in ultrapure water with Na 2 SO 4 were performed to assess the effect of current density, as well as supporting electrolyte and dye concentrations. At 100 mA cm −2 , solutions of 130 mL of 254 mg L −1 of the dye in 0.05 M Na 2 SO 4 became colourless and totally mineralized after 50 and 240 min, respectively, which can be explained by the synergistic action of BDD( • OH) at the anode surface and homogeneous • OH formed in the bulk from Fenton's reaction promoted in the presence of Fe 2+ catalyst. Furthermore, UVA photons induced the continuous Fe 2+ regeneration and photolytic decomposition of refractory intermediate complexes. In that aqueous matrix, the cleavage of the dye molecules proceeded through several reaction routes to yield N-containing and non-N-containing derivatives with one or two aromatic rings, short-chain aliphatic carboxylic acids and inorganic ions. Oxalic and oxamic acids and sulfate ions were accumulated at different rates in EO-H 2 O 2 , EF and PEF. The three methods allowed the progressive decontamination of Ponceau 4R solutions in a real water matrix even without the addition of electrolyte, although complete TOC abatement after 360 min at 33.3 mA cm −2 was only ensured by the iron-catalyzed PEF process.