Use of Pt and boron-doped diamond anodes in the electrochemical advanced oxidation of Ponceau SS diazo dye in acidic sulfate medium

The electrochemical degradation of 2.5 L of solutions of Ponceau SS diazo dye in acidic sulfate medium has been studied in a pre-pilot flow plant with a BDD/air-diffusion or Pt/air-diffusion cell connected to an annular photoreactor. The decolorization and mineralization was enhanced in the order: electrochemical oxidation with electrogenerated H2O2 < electro-Fenton < photoelectro-Fenton. The two former methods performed better with the BDD anode, whereas the latter one yielded similar results for both anodes. From this, the use of less expensive active anodes like Ti|Pt instead of non-active BDD for photo-assisted Fenton-based electrochemical processes is recommended. In all methods, increasing current density led to greater degradation rate, but with lower mineralization current efficiency and higher energy consumption. Five primary aromatic products and four final carboxylic acids were detected, along with recalcitrant products poorly removed by hydroxyl radicals and UVA radiation